research about junk food

Frontiers for Young Minds

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The Impacts of Junk Food on Health

Energy-dense, nutrient-poor foods, otherwise known as junk foods, have never been more accessible and available. Young people are bombarded with unhealthy junk-food choices daily, and this can lead to life-long dietary habits that are difficult to undo. In this article, we explore the scientific evidence behind both the short-term and long-term impacts of junk food consumption on our health.

Introduction

The world is currently facing an obesity epidemic, which puts people at risk for chronic diseases like heart disease and diabetes. Junk food can contribute to obesity and yet it is becoming a part of our everyday lives because of our fast-paced lifestyles. Life can be jam-packed when you are juggling school, sport, and hanging with friends and family! Junk food companies make food convenient, tasty, and affordable, so it has largely replaced preparing and eating healthy homemade meals. Junk foods include foods like burgers, fried chicken, and pizza from fast-food restaurants, as well as packaged foods like chips, biscuits, and ice-cream, sugar-sweetened beverages like soda, fatty meats like bacon, sugary cereals, and frozen ready meals like lasagne. These are typically highly processed foods , meaning several steps were involved in making the food, with a focus on making them tasty and thus easy to overeat. Unfortunately, junk foods provide lots of calories and energy, but little of the vital nutrients our bodies need to grow and be healthy, like proteins, vitamins, minerals, and fiber. Australian teenagers aged 14–18 years get more than 40% of their daily energy from these types of foods, which is concerning [ 1 ]. Junk foods are also known as discretionary foods , which means they are “not needed to meet nutrient requirements and do not belong to the five food groups” [ 2 ]. According to the dietary guidelines of Australian and many other countries, these five food groups are grains and cereals, vegetables and legumes, fruits, dairy and dairy alternatives, and meat and meat alternatives.

Young people are often the targets of sneaky advertising tactics by junk food companies, which show our heroes and icons promoting junk foods. In Australia, cricket, one of our favorite sports, is sponsored by a big fast-food brand. Elite athletes like cricket players are not fuelling their bodies with fried chicken, burgers, and fries! A study showed that adolescents aged 12–17 years view over 14.4 million food advertisements in a single year on popular websites, with cakes, cookies, and ice cream being the most frequently advertised products [ 3 ]. Another study examining YouTube videos popular amongst children reported that 38% of all ads involved a food or beverage and 56% of those food ads were for junk foods [ 4 ].

What Happens to Our Bodies Shortly After We Eat Junk Foods?

Food is made up of three major nutrients: carbohydrates, proteins, and fats. There are also vitamins and minerals in food that support good health, growth, and development. Getting the proper nutrition is very important during our teenage years. However, when we eat junk foods, we are consuming high amounts of carbohydrates, proteins, and fats, which are quickly absorbed by the body.

Let us take the example of eating a hamburger. A burger typically contains carbohydrates from the bun, proteins and fats from the beef patty, and fats from the cheese and sauce. On average, a burger from a fast-food chain contains 36–40% of your daily energy needs and this does not account for any chips or drinks consumed with it ( Figure 1 ). This is a large amount of food for the body to digest—not good if you are about to hit the cricket pitch!

• Figure 1 - The nutritional composition of a popular burger from a famous fast-food restaurant, detailing the average quantity per serving and per 100 g.
• The carbohydrates of a burger are mainly from the bun, while the protein comes from the beef patty. Large amounts of fat come from the cheese and sauce. Based on the Australian dietary guidelines, just one burger can be 36% of the recommended daily energy intake for teenage boys aged 12–15 years and 40% of the recommendations for teenage girls 12–15 years.

A few hours to a few days after eating rich, heavy foods such as a burger, unpleasant symptoms like tiredness, poor sleep, and even hunger can result ( Figure 2 ). Rather than providing an energy boost, junk foods can lead to a lack of energy. For a short time, sugar (a type of carbohydrate) makes people feel energized, happy, and upbeat as it is used by the body for energy. However, refined sugar , which is the type of sugar commonly found in junk foods, leads to a quick drop in blood sugar levels because it is digested quickly by the body. This can lead tiredness and cravings [ 5 ].

• Figure 2 - The short- and long-term impacts of junk food consumption.
• In the short-term, junk foods can make you feel tired, bloated, and unable to concentrate. Long-term, junk foods can lead to tooth decay and poor bowel habits. Junk foods can also lead to obesity and associated diseases such as heart disease. When junk foods are regularly consumed over long periods of time, the damages and complications to health are increasingly costly.

Fiber is a good carbohydrate commonly found in vegetables, fruits, barley, legumes, nuts, and seeds—foods from the five food groups. Fiber not only keeps the digestive system healthy, but also slows the stomach’s emptying process, keeping us feeling full for longer. Junk foods tend to lack fiber, so when we eat them, we notice decreasing energy and increasing hunger sooner.

Foods such as walnuts, berries, tuna, and green veggies can boost concentration levels. This is particularly important for young minds who are doing lots of schoolwork. These foods are what most elite athletes are eating! On the other hand, eating junk foods can lead to poor concentration. Eating junk foods can lead to swelling in the part of the brain that has a major role in memory. A study performed in humans showed that eating an unhealthy breakfast high in fat and sugar for 4 days in a row caused disruptions to the learning and memory parts of the brain [ 6 ].

Long-Term Impacts of Junk Foods

If we eat mostly junk foods over many weeks, months, or years, there can be several long-term impacts on health ( Figure 2 ). For example, high saturated fat intake is strongly linked with high levels of bad cholesterol in the blood, which can be a sign of heart disease. Respected research studies found that young people who eat only small amounts of saturated fat have lower total cholesterol levels [ 7 ].

Frequent consumption of junk foods can also increase the risk of diseases such as hypertension and stroke. Hypertension is also known as high blood pressure and a stroke is damage to the brain from reduced blood supply, which prevents the brain from receiving the oxygen and nutrients it needs to survive. Hypertension and stroke can occur because of the high amounts of cholesterol and salt in junk foods.

Furthermore, junk foods can trigger the “happy hormone,” dopamine , to be released in the brain, making us feel good when we eat these foods. This can lead us to wanting more junk food to get that same happy feeling again [ 8 ]. Other long-term effects of eating too much junk food include tooth decay and constipation. Soft drinks, for instance, can cause tooth decay due to high amounts of sugar and acid that can wear down the protective tooth enamel. Junk foods are typically low in fiber too, which has negative consequences for gut health in the long term. Fiber forms the bulk of our poop and without it, it can be hard to poop!

Tips for Being Healthy

One way to figure out whether a food is a junk food is to think about how processed it is. When we think of foods in their whole and original forms, like a fresh tomato, a grain of rice, or milk squeezed from a cow, we can then start to imagine how many steps are involved to transform that whole food into something that is ready-to-eat, tasty, convenient, and has a long shelf life.

For teenagers 13–14 years old, the recommended daily energy intake is 8,200–9,900 kJ/day or 1,960 kcal-2,370 kcal/day for boys and 7,400–8,200 kJ/day or 1,770–1,960 kcal for girls, according to the Australian dietary guidelines. Of course, the more physically active you are, the higher your energy needs. Remember that junk foods are okay to eat occasionally, but they should not make up more than 10% of your daily energy intake. In a day, this may be a simple treat such as a small muffin or a few squares of chocolate. On a weekly basis, this might mean no more than two fast-food meals per week. The remaining 90% of food eaten should be from the five food groups.

In conclusion, we know that junk foods are tasty, affordable, and convenient. This makes it hard to limit the amount of junk food we eat. However, if junk foods become a staple of our diets, there can be negative impacts on our health. We should aim for high-fiber foods such as whole grains, vegetables, and fruits; meals that have moderate amounts of sugar and salt; and calcium-rich and iron-rich foods. Healthy foods help to build strong bodies and brains. Limiting junk food intake can happen on an individual level, based on our food choices, or through government policies and health-promotion strategies. We need governments to stop junk food companies from advertising to young people, and we need their help to replace junk food restaurants with more healthy options. Researchers can focus on education and health promotion around healthy food options and can work with young people to develop solutions. If we all work together, we can help young people across the world to make food choices that will improve their short and long-term health.

Obesity : ↑ A disorder where too much body fat increases the risk of health problems.

Processed Food : ↑ A raw agricultural food that has undergone processes to be washed, ground, cleaned and/or cooked further.

Discretionary Food : ↑ Foods and drinks not necessary to provide the nutrients the body needs but that may add variety to a person’s diet (according to the Australian dietary guidelines).

Refined Sugar : ↑ Sugar that has been processed from raw sources such as sugar cane, sugar beets or corn.

Saturated Fat : ↑ A type of fat commonly eaten from animal sources such as beef, chicken and pork, which typically promotes the production of “bad” cholesterol in the body.

Dopamine : ↑ A hormone that is released when the brain is expecting a reward and is associated with activities that generate pleasure, such as eating or shopping.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

[1] ↑ Australian Bureau of Statistics. 2013. 4324.0.55.002 - Microdata: Australian Health Survey: Nutrition and Physical Activity, 2011-12 . Australian Bureau of Statistics. Available online at: http://bit.ly/2jkRRZO (accessed December 13, 2019).

[2] ↑ National Health and Medical Research Council. 2013. Australian Dietary Guidelines Summary . Canberra, ACT: National Health and Medical Research Council.

[3] ↑ Potvin Kent, M., and Pauzé, E. 2018. The frequency and healthfulness of food and beverages advertised on adolescents’ preferred web sites in Canada. J. Adolesc. Health. 63:102–7. doi: 10.1016/j.jadohealth.2018.01.007

[4] ↑ Tan, L., Ng, S. H., Omar, A., and Karupaiah, T. 2018. What’s on YouTube? A case study on food and beverage advertising in videos targeted at children on social media. Child Obes. 14:280–90. doi: 10.1089/chi.2018.0037

[5] ↑ Gómez-Pinilla, F. 2008. Brain foods: the effects of nutrients on brain function. Nat. Rev. Neurosci. 9, 568–78. doi: 10.1038/nrn2421

[6] ↑ Attuquayefio, T., Stevenson, R. J., Oaten, M. J., and Francis, H. M. 2017. A four-day western-style dietary intervention causes reductions in hippocampal-dependent learning and memory and interoceptive sensitivity. PLoS ONE . 12:e0172645. doi: 10.1371/journal.pone.0172645

[7] ↑ Te Morenga, L., and Montez, J. 2017. Health effects of saturated and trans-fatty acid intake in children and adolescents: systematic review and meta-analysis. PLoS ONE. 12:e0186672. doi: 10.1371/journal.pone.0186672

[8] ↑ Reichelt, A. C. 2016. Adolescent maturational transitions in the prefrontal cortex and dopamine signaling as a risk factor for the development of obesity and high fat/high sugar diet induced cognitive deficits. Front. Behav. Neurosci. 10. doi: 10.3389/fnbeh.2016.00189

• Systematic Review
• Open access
• Published: 12 June 2024

Association between junk food consumption and mental health problems in adults: a systematic review and meta-analysis

• Hanieh-Sadat Ejtahed 1 , 2 ,
• Parham Mardi 3 ,
• Bahram Hejrani 4 ,
• Fatemeh Sadat Mahdavi 5 , 6 ,
• Behnaz Ghoreshi 7 ,
• Kimia Gohari 8 ,
• Motahar Heidari-Beni 9 &
• Mostafa Qorbani 7 , 10  

BMC Psychiatry volume  24 , Article number:  438 ( 2024 ) Cite this article

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Anxiety and depression can seriously undermine mental health and quality of life globally. The consumption of junk foods, including ultra-processed foods, fast foods, unhealthy snacks, and sugar-sweetened beverages, has been linked to mental health. The aim of this study is to use the published literature to evaluate how junk food consumption may be associated with mental health disorders in adults.

A systematic search was conducted up to July 2023 across international databases including PubMed/Medline, ISI Web of Science, Scopus, Cochrane, Google Scholar, and EMBASE. Data extraction and quality assessment were performed by two independent reviewers. Heterogeneity across studies was assessed using the I 2 statistic and chi-square-based Q-test. A random/fixed effect meta-analysis was conducted to pool odds ratios (ORs) and hazard ratios (HRs).

Of the 1745 retrieved articles, 17 studies with 159,885 participants were suitable for inclusion in the systematic review and meta-analysis (seven longitudinal, nine cross-sectional and one case-control studies). Quantitative synthesis based on cross-sectional studies showed that junk food consumption increases the odds of having stress and depression (OR = 1.15, 95% CI: 1.06 to 1.23). Moreover, pooling results of cohort studies showed that junk food consumption is associated with a 16% increment in the odds of developing mental health problems (OR = 1.16, 95% CI: 1.07 to 1.24).

Meta-analysis revealed that consumption of junk foods was associated with an increased hazard of developing depression. Increased consumption of junk food has heightened the odds of depression and psychological stress being experienced in adult populations.

Peer Review reports

Psychological conditions such as bipolar affective disorder, eating disorders, anxiety disorders, and depressive disorders impose a considerable burden across the international community, adversely affecting quality of life [ 1 , 2 ]. Psychological problems including depression, stress, and anxiety, also arise in association with some non-communicable diseases including cardiovascular disease (CVD), stroke, and cancer [ 3 ]. All of these mental health problems have adverse effects on health status, quality of life, and ability to work [ 4 ].

Genetics, socioeconomic status, exercise habits, diet, and nutritional status, are understood to be key contributors to the development of emotional or behavioral problems [ 5 ]. Food-mood relationships underpin well-known pathways, suggesting that unhealthy eating habits and poor nutritional status are correlated with various mental health problems and behavioral disturbances in adults [ 6 ]. This infers that mood and psychological health may be influenced by nutritional habits [ 7 ].

The world-wide consumption of junk foods, which include ultra-processed foods, fast foods, unhealthy snacks, and sugar-sweetened beverages, is increasing. The hallmarks of junk foods are that they have high levels of energy, fat, sugar, and salt, accompanied by low levels of micronutrients, fiber, and other bioactive compounds [ 8 ]. The low nutritional value of junk foods can alter inflammatory pathways, leading to an increase in biomarkers for oxidative stress and inflammation, which contribute to biological changes associated with mental health disorders. In vitro studies have demonstrated that junk food consumption can negatively affect the brain and mental health [ 9 , 10 ].

However, the findings of epidemiological studies are inconsistent. Some studies showed the significant association between junk foods consumption and mental health disorders. However, other studies did not mention any relationship [ 4 , 11 , 12 ]. The aim of this study is to examine the relationship between junk food consumption and mental health disorders in adults by conducting a systematic review and meta-analysis of published studies to date.

The current systematic review and meta-analysis study was conducted according to the PRISMA 2020 statement (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) [ 13 , 14 ], included studies assessing the relationship between junk food consumption and mental health in adults.

Search strategy

A systematic literature search was conducted in PubMed/Medline, ISI Web of Science, Scopus, Cochrane, Google Scholar, and EMBASE up to July 2023. The following keywords were used in this search: “sweetened drink*” OR “sweetened beverage*” OR snack* OR “processed food*” OR “junk food*” OR “soft drinks” OR “sugared beverages” OR “fried foods” OR “instant foods” OR sweets for junk food consumption and “mental health” OR depression OR stress OR anxiety OR “sleep dissatisfaction” OR “sleep disorders” OR happiness OR wellbeing for mental health status. In PubMed, keywords were searched through [tiab] and [MeSH] tags. Articles were required to be written in English language; there was no limitation regarding the year of publication. The reference lists of included papers were also examined to avoid missing other published data.

Inclusion and exclusion criteria

Two investigators independently screened the articles retrieved during the literature search. Publications that fulfilled the following criteria were eligible for inclusion: (1) observational studies that were conducted in adults (cohort, case-control, cross-sectional); and (2) studies that examined the relationship between junk food consumption and mental health status. We excluded letters, comments, reviews, meta-analyses, ecological, in vitro, and pre-clinical studies, as well as duplicate studies.

Data extraction

For each eligible study, the following information was extracted: first author, year of publication, study design, country, age range, gender, sample size, type of junk food, dietary assessment tool, mental health parameters, mental health assessment tool, study quality score, effect sizes and measures, and covariates.

It should be noted that in the present study, junk food intake was considered using four categories: (i) sweet drinks (fruit-flavored drinks, sweetened coffee, fruit juice drinks, sugared coffee and tea, energy drinks, cola drinks, beverages, soft drinks, lemonade, and soda), (ii) sweet snacks (total sugars, added sugars, sweetened desserts, fatty/sweet products, ice cream, chocolate, artificial sweeteners, sweet snacks, dessert, sauces and dressings, candy, patterns of consumption of sweet, high fat and sugary foods, biscuits and pastries, cakes, pie/cookies, and baked goods), (iii) snacks (including snacks, sauces/added fats, fast food, fast-food pattern, western diet pattern, snacking and convenience pattern, fried foods, fried potato, crisps, salty snacks, convenience pattern, instant foods), and (iv) total junk foods (all types of junk foods).

Quality assessment of studies

The quality of the included studies was examined using the Newcastle-Ottawa Scale (NOS) [ 15 , 16 ]. The NOS assigns a maximum of 9 points to each study: 4 for selection, 2 for comparability, and 3 for assessment of outcomes (for cohort study) or exposures (for case-control study).

The maximum score for cohort and case-control studies were 9 and for cross-sectional studies were 7. In the current analysis, the quality of studies is defined good if the studies get 3 or 4 stars in the selection domain AND 1 or 2 stars in the comparability domain AND 2 or 3 stars in the outcome/exposure domain. Besides, fair quality is defined as 2 stars in the selection domain AND 1 or 2 stars in the comparability domain AND 2 or 3 stars in the outcome/exposure domain and finally, poor quality is defined for 0 or 1 star in the selection domain OR 0 star in the comparability domain OR 0 or 1 star in the outcome/exposure domain.

All steps including searching, article screening, data extraction, and quality assessment of articles were independently performed by two investigators. Disagreements between the two investigators were resolved by discussion to reach consensus.

Statistical analysis

The results of the current quantitative synthesis are presented as hazard ratios (HRs) or odds ratios (ORs) and 95% confidence intervals (95% CI). STATA version 14.0 (StataCorp, College Station, TX) software was used to perform the meta-analysis. We conducted meta-analysis whenever at least two studies investigated similar associations between junk food consumption and mental health problems.

I 2 statistic and chi-square-based Q-test were used for the assessment of heterogeneity. In the current study, a lack of heterogeneity was inferred when the p-value of chi-square-based Q-test exceeded 0.10. Fixed models were used to pool HRs and ORs when the heterogeneity p-value was higher than 0.10. Random models were used to pool the ORs whenever the heterogeneity p-value was equal to or less than 0.10, followed by Galbraith analysis and sensitivity analysis. Subgroup analysis was also conducted to identify the source of heterogeneity. Publication bias was measured using Begg’s test or Egger’s test and considered substantial whenever the resulting p-value was < 0.1.

Systematic search results

The flow diagram for the process of study selection is shown in the PRISMA flowchart (Fig.  1 ). Based on the initial search, we found 1745 papers. After removal of duplicate documents and title and abstract screening, 69 articles remained for more detailed assessment. Full texts of these papers were reviewed carefully by three researchers, with 17 articles satisfying the eligibility requirements for inclusion in the systematic review and meta-analysis.

The PRISMA flowchart for the process of study selection

Characteristics of the included studies

Seventeen studies evaluating a total of 159,885 participants were included in our quantitative synthesis. A considerable number of participants were female, with seven articles restricted to female participants. Most of the included studies were cross-sectional (58.82%), with the remaining seven (47.05%) being cohort studies. It should be noted that Reinks et al. (2013) presented both cross-sectional and longitudinal data. Reinks et al. (2013) and ten other papers (64.70% in total) assessed depression as an outcome. Nine (52.94%) of studies assessed anxiety or stress as outcomes. In terms of dietary exposures, various types of junk foods such as ultra-processed food, beverages, and snacks were evaluated across the 17 studies. Table  1 illustrates detailed characteristics of records including the age of participants and provenance of studies. All of the included studies have good quality.

Qualitative synthesis

Most of the included studies concordantly showed at least a single significant link between junk food consumption and psychological outcomes. This was despite their use of different measures of association, dissimilar exposure duration and outcomes, and heterogenous definitions, all of which made it challenging to draw conclusions from the qualitative synthesis (summarized in Table  2 ). Nevertheless, findings from some studies were discordant. For instance, while Sangsefidi et al. (2020) and Chaplin et al. (2011) demonstrated a significant association between stress and snack intake, Almajwal et al. (2016) and Zenk et al. (2014) reported non-significant findings, despite the use of similar measures of association and comparable adjustments for covariates. Although a notable number of studies showed a significant link between junk food intake and psychological disorders, the level of disagreement across studies meant that a meta-analysis was essential in order to clarify this relationship.

Quantitative synthesis

Pooling or in cross-sectional studies.

Four cross-sectional studies ( n  = 13,500) demonstrated that junk food consumption was associated with increased stress (pooled OR = 1.33, 95% CI: 1.02 to 1.65). This finding shows a significant association; however, a notable level of heterogeneity was observed (I² = 74.3%, p  = 0.009) (Fig.  2 ; Table  3 ). Also, six cross-sectional studies, including 74,127 participants, illustrated a significant association between junk food consumption and depression, with a pooled OR of 1.16 (95% CI: 1.04 to 1.28) (Fig.  2 ). Overall, junk food consumption indicated a significant association with increased odds of mental health problems (OR = 1.15, 95% CI: 1.06 to 1.23). The Egger’s test for small-study effects indicated evidence of publication bias ( p  > 0.001). To address this bias, a trim and fill analysis was conducted, resulting in an adjusted OR of 1.11 (95% CI: 0.95 to 1.30). Funnel plot is presented in Fig.  3 .

Junk food consumption (unhealthy snacks and sweetened beverages) and odds of having depression and stress in cross-sectional studies

Funnel plot, using data from cross-sectional studies investigating the association between junk food consumption and mental health problems

Pooling PR in cross-sectional studies

Two cross-sectional studies focusing on stress with a combined sample size of 2,232 participants reported a PR of 1.31 (95% CI: 1.07–1.55) (Fig.  4 ).

Association between junk foods consumption and having stress in cross-sectional studies

Pooling OR in cohort studies

Pooling results of cohort studies showed that junk food consumption significantly increases the odds of depression by 15% (OR = 1.15; 95% CI: 1.06 to 1.24). After inclusion of the single cohort study that considered stress as its outcome, the overall OR of junk foods consumption and mental disorders was 1.16 (OR = 1.16, 95% CI: 1.07 to 1.24) (Fig.  5 ).

Association between junk foods consumption and having mental health problems in cohort studies

Although Egger’s test for small-study effects yielded a bias coefficient of 2.53, standard error of 1.19, and a p-value of 0.07, trim and fill analysis did not impute any studies, and the overall OR remained unchanged. Figure  6 demonstrates the funnel plot.

Funnel plot, using data from cohort studies investigating the association between junk food consumption and mental health problems

Pooling HR in cohort studies

Aggregating two cohort studies with 41,637 participants showed an HR of 1.30 (95% CI: 1.15 to 1.45) for depression, demonstrating a significant risk increase (Fig.  7 ). Remarkably, these studies showed no heterogeneity (I² = 0.0%, p  = 0.81) or publication bias.

Junk food consumption and risk of depression in cohort studies

The meta-analysis reported in the present study showed that high consumption of junk foods was significantly associated with increased risks of depression. In addition, higher junk food consumption was associated with increased odds of depression and psychological stress. This association between consumption of food with low nutritional value and mental health was demonstrated in multiple studies on different populations and cultures [ 17 , 18 , 19 ].

Meta-analysis of prospective studies showed that increased risk of subsequent depression and adverse mental health outcomes were correlated with higher ultra-processed food intake [ 20 ]. According to meta analysis incorporating seven studies, junk food consumption increased the risk of experiencing mental illness symptoms [ 21 ]. For example, one study reporting outcomes for 1591 adults, demonstrated that high consumption of fast foods and processed foods was associated with anxiety, nervousness, restlessness, lack of motivation and depressive symptoms [ 22 ]. In another study, weight gain due to unhealthy eating was associated with deterioration in mental health in 404 adults during the second year of the COVID-19 pandemic [ 23 ]. Our findings are consistent with a recent systematic review and dose-response meta-analysis that included 26 studies and 260,385 participants from twelve countries, which showed that ultra-processed food consumption increased risk of depression [ 24 ].

Epidemiological data suggests that unhealthy food consumption may be associated with poorer mental health through its adverse effects on inflammatory processes, nutritional status, and neurotransmitter function. Inflammation has previously been associated with underlying biological bases for depression [ 25 ]. Several observational and meta-analysis studies have demonstrated an inverse association between the consumption of healthy foods including vegetables, fruits, whole-grain and fish, with depressive symptoms [ 26 , 27 , 28 , 29 ]. Healthy dietary patterns include a significant amount of tryptophan, an essential amino acid and precursor to serotonin; evidence shows that reduction in the availability of serotonin is associated with depression [ 30 , 31 ].

The adoption of western dietary patterns that regularly include junk foods and fast foods can increase the probability of developing inflammatory and cardiovascular diseases. Inflammatory conditions are related to mental health disorders including depression, stress and anxiety [ 32 , 33 ]. In addition, life stressors may augment the interconnection between depressive mood and unhealthy dietary patterns through activation of the brain’s reward system by foods that are high in sugar, fat, and salt [ 34 ].

There is also evidence that brain-derived neurotrophic factor (BDNF) may be reduced by consumption of a high fat diet. BDNF is associated with supporting existing neurons and the production of new neurons and implicated in the pathogenesis of depressive disorder. A reduction in BDNF impairs synaptic and cognitive function and neuronal growth, contributing to the development of psychological disorders [ 35 ]. Western-type diets include a higher amount of polyunsaturated omega-6 fatty acids, which increase proinflammatory eicosanoids, and decrease BDNF and neuronal membrane fluidity [ 36 ]. This suggests that the adverse effects of junk and fast foods on mental health might be associated with the high content of unhealthy fats contained in these foods [ 4 ]. Moreover, intake of high amounts of sugar through consumption of sweet drinks and snacks can lead to endothelial dysfunction, inflammation, and exaggerated insulin production that may also influence mood [ 37 , 38 , 39 , 40 ].

Mood disorder may itself influence diet, with some studies reporting that patients with depression consume a large amount of carbohydrate-fat-rich foods during their depressive episodes [ 41 , 42 , 43 ]. Serotonin, an important neurotransmitter for regulating mood, may play a prominent role in this respect given that the sole source of its precursor, tryptophan, is through the diet [ 44 ].

The consumption of ultra-processed foods is positively correlated with unhealthy eating habits, including lower intake of fruits and vegetables and higher intake of sweet foods or beverages [ 8 , 45 ]. It is notable that ultra-processed foods contain additives as well as molecules that are generated by high-temperature heating. These can alter gut microbiota composition and reduce nutrient absorption [ 46 ]. Some studies have explored the association between the gut microbiome and mental health [ 47 , 48 , 49 ], with animal studies suggesting that food additives might increase symptoms of and susceptibility to anxiety and depression via changes of gut microbiota composition [ 50 , 51 ].

The present paper found that the outcomes of studies selected for the meta-analysis were not always in agreement. This may have been due to confounding factors such as past history of depression or negative life events not being included in the analysis, differences in study designs, sample sizes or population characteristics, non-homogeneous assessment of dietary patterns, and inconsistencies in the evaluation of psychological disorders including the use of different diagnostic criteria to define mental health status.

On the other side, some studies have reported that mental health disorders including depression and psychological stress may reduce an individual’s motivation to eat healthy foods and sometime lead to overeating [ 17 ], skipping main meals and replacing them with high calories foods [ 30 ]. Some individuals consume high energy and fatty foods during stressful situations, choosing these more palatable foods as an unconscious or deliberate strategy to change their energy levels and mood [ 52 , 53 ]. Stress affects neuroendocrine function by activating the hypothalamic-pituitary-adrenal (HPA) axis, increasing the secretion of glucocorticoids. These change glucose metabolism, promote insulin resistance, and alter the secretion of appetite-related hormones. All of these factors contribute to the propensity to eat more high-calorie palatable food [ 12 ]. However, there are also studies that report no differences in eating patterns under stressful and non-stressful conditions [ 54 , 55 ]. The analysis presented in the present study cannot be used to demonstrate causality. On the basis of the evidence, it is plausible that there is a bidirectional relationship between junk food consumption and mental health [ 17 ]. It remains unclear whether the quality of food choices affects susceptibility to poorer mental health outcomes, and/or the experience of unpleasant emotions influences the quality of food selection [ 30 ]. Evidence for a causal pathway is unclear and needs to be further investigated in well-controlled longitudinal studies. Our meta-analysis on cross-sectional studies showed an association between junk food consumption and increased odds of having stress and depression. Besides, meta-analysis on cohort studies demonstrated that junk foods consumption increases the risk of developing stress and depression.

Strengths and limitations

As the main strength of our study, we have comprehensively and specifically evaluated earlier findings regarding the association between junk food consumption and mental health status in adults. The present study has some limitations arising from the studies selected for meta-analysis. Inconsistencies in design of studies such as the ways that diet is assessed using different dietary questionnaire tools, the influence of seasonal and hormonal variations of depressive symptoms, and the use of different diagnostic criteria for defining mental health status is one of the limitations of this study. Despite the association shown between consumption of junk foods and mental health disorders, the strength of the associations and number of documents included in this study is unable to demonstrate causality.

The present study supports the conclusion that consumption of junk foods that are high in fat and sugar content and of low nutritive value are associated with poorer mental health in adults. Further studies utilizing a longitudinal design are needed to better determine the directionality and effect size of junk food consumption on psychological disorders. Moreover, more studies are warranted to assess the mechanisms involved in this relationship to provide scientific support for changes in public health policies.

Data availability

Data will be made available on request from the authors.

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Acknowledgements

We would like to thank Dr. Jillian Broadbear for their invaluable contribution in editing and reviewing this manuscript.

The authors gratefully acknowledge funding provided by the Alborz University of Medical Sciences.

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Ejtahed, HS., Mardi, P., Hejrani, B. et al. Association between junk food consumption and mental health problems in adults: a systematic review and meta-analysis. BMC Psychiatry 24 , 438 (2024). https://doi.org/10.1186/s12888-024-05889-8

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New review unpacks what we know about junk food and 32 health issues

We have long been told that junk food is bad for us.

But a new review by experts at leading Australian and international institutions sheds light on just how damaging a diet of instant noodles, chips, fast food and ready-made meals can be.

The researchers delved into the results of 45 previous studies, published over the past three years, involving almost 10 million participants.

Considered the largest review of its kind, researchers found "strong evidence" that eating ultra-processed foods can put you at higher risk of 32 different health problems, both physical and mental   —   and even early death.

After what they call "staggering statistics" that reveal "a troubling reality", the research,  published in the BMJ , is calling for UN agencies to take stronger action.

And the experts want countries like Australia to adopt similar measures used to curb smoking.

Let's unpack what they found. 

What are considered ultra-processed foods?

The umbrella review used the Nova food classification system to define ultra-processed foods (UPF).

Nova is a widely used system that aims at classifying food products according to the nature, extent and purpose of industrial processing.

It classes UPFs as a broad range of ready-to-eat products, including packaged snacks, soft drinks, instant noodles, and ready-made meals.

Researchers also specifically mentioned foods such as packaged baked goods, ice-cream, sugary cereal, chips, lollies and biscuits. 

These types of products are characterised as "industrial formulations".

Essentially, UPFs are "products made up of foods that have undergone significant processing and no longer resemble the raw ingredients," said Charlotte Gupta from the Appleton Institute at Central Queensland University.

UPFs are primarily composed of chemically modified substances extracted from foods, along with additives to enhance taste, texture, appearance and durability, with minimal to no inclusion of whole foods.

They also tend to be high in added sugar, fat, and salt, and low in vitamins and fibre.

How much do Australians consume ultra-processed foods?

Based on analyses of worldwide UPF sales data and consumption, the review said there was a shift towards an increasingly ultra-processed global diet.

However, there were considerable differences across countries and regions.

In high-income countries including Australia and the US, the share of dietary energy derived from UPFs ranges from 42 per cent and 58 per cent, respectively. 

"Ultra-processed foods, laden with additives and sometimes lacking in essential nutrients, have become ubiquitous in the Australian diet," said Daisy Coyle, research fellow and accredited practising dietitian at The George Institute for Global Health. 

"In fact, they make up almost half of what we buy at the supermarket."

The total energy intake from UPFs was as low as 10 per cent and 25 per cent in Italy and South Korea, the review found. 

Whereas, for low- and middle-income countries such as Colombia and Mexico, the total energy intake ranged from 16 to 30 per cent. 

What are junk foods putting us at risk of?

Overall, the review found that higher exposure to UPFs was consistently associated with an increased risk of 32 adverse health outcomes.

These include cancer, major heart and lung conditions, mental health disorders, and early death.

The researchers stressed that this kind of study "cannot prove the junk food is causing the health problems".

However, they say there is consistent evidence that these types of junk foods are "associated with death of any cause" and specific health conditions.

"While these associations are interesting and warrant further high quality research, they do not and cannot provide evidence of causality," Alan Barclay, a consultant dietitian and nutritionist from the University of Sydney, said in a statement to the Australian Science Media Centre.  

The review found "convincing evidence" higher junk food intake was associated with:

• About a 50 per cent increased risk of cardiovascular disease-related death
• A 48 to 53 per cent higher risk of anxiety and common mental disorders
• A 12 per cent greater risk of type 2 diabetes 

There was "highly suggestive evidence" for:

• A 21 per cent greater risk of death from any cause
• A 40 to 66 per cent increased risk of heart disease-related death, obesity, type 2 diabetes, and sleep problems
• A 22 per cent increased risk of depression.

"The statistics are staggering – these foods may double your risk of dying from heart disease or from developing a mental health disorder," Dr Coyle said. 

There was also evidence for associations between UPFs and asthma, gastrointestinal health, and cardiometabolic diseases but the evidence was limited.

The researchers acknowledged that there were limitations with an umbrella review and they couldn't rule out the possibility that other factors and variations assessing UPF intake may have influenced their results.

Does Australia need to take a tobacco approach to junk food?

The researchers say the findings call for urgent research and public health actions to minimise ultra-processed food consumption.

They want United Nations agencies to consider a framework similar to the approaches taken to tobacco.  

For instance, including warning labels on food packaging, restricting advertising and banning junk food being sold near schools.

Currently, Australia has voluntary programs which encourage companies to cut the salt, sugar and fat level from their foods.

There are also health star ratings on foods, but only around 40 per cent of products carry the labels, Dr Coyle told the ABC.

She said more needs to be done to enforce these measures and make them mandatory. 

"Existing nutrition policies in Australia aren’t enough to tackle this problem," she said. 

"We've put up with voluntary measures and they don't work we don't see changes … Australia is not going in a healthy direction." 

Putting warning labels on food, like what we have on cigarette packets, has been effective in places like South America, Dr Coyle said. 

Because they are designed to put consumers off purchasing unhealthy products, they put pressure on companies to make improvements to their food. 

"Companies don't want to put them on their product so they cut levels of salt and sugar, for instance," she said. 

The ABC has reached out to the Australian Food and Grocery Council for comment. 

Researchers say there also needs to be more consideration around availability and access to fresh and healthy food.

And more support should be provided to family farmers, and independent businesses that grow, make, and sell unprocessed or minimally processed foods.

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Children's Health

If you think kids are eating mostly junk food, a new study finds you're right.

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Researchers found that 67% of calories consumed by children and adolescents in the U.S. came from ultra-processed foods in 2018, a jump from 61% in 1999. The nationwide study analyzed the diets of 33,795 children and adolescents. Drazen Stader / EyeEm/Getty Images hide caption

Researchers found that 67% of calories consumed by children and adolescents in the U.S. came from ultra-processed foods in 2018, a jump from 61% in 1999. The nationwide study analyzed the diets of 33,795 children and adolescents.

Kids and teens in the U.S. get the majority of their calories from ultra-processed foods like frozen pizza, microwavable meals, chips and cookies, a new study has found.

Two-thirds — or 67% — of calories consumed by children and adolescents in 2018 came from ultra-processed foods, a jump from 61% in 1999, according to a peer-reviewed study published in the medical journal JAMA . The research, which analyzed the diets of 33,795 youths ages 2 to 19 across the U.S., noted the "overall poorer nutrient profile" of the ultra-processed foods.

"This is particularly worrisome for children and adolescents because they are at a critical life stage to form dietary habits that can persist into adulthood," says Fang Fang Zhang , the study's senior author and a nutrition and cancer epidemiologist at Tufts University's Friedman School of Nutrition Science and policy. "A diet high in ultra-processed foods may negatively influence children's dietary quality and contribute to adverse health outcomes in the long term."

It's Not Just Salt, Sugar, Fat: Study Finds Ultra-Processed Foods Drive Weight Gain

One reason for the increase may be the convenience of ultra-processed foods, Zhang says. Industrial processing, such as changing the physical structure and chemical composition of foods, not only gives them a longer shelf life but also a more appetizing taste.

"Things like sugar, corn syrup, some hemp oil and other ingredients that we usually don't usually use in our kitchen, that are extracted from foods and synthesized in the laboratory, those are being added in the final product of ultra-processed foods," Zhang said. "A purpose of doing this is to make them highly palatable. So kids will like those foods that somehow make it hard to resist."

Shots - Health News

Cheap, legal and everywhere: how food companies get us 'hooked' on junk.

During the same two-decade period when the study data was collected, the consumption of unprocessed or minimally processed foods decreased to 23.5% from 28.8%, the study found.

The greatest increase in calories came from ready-to-eat or ready-to-heat meals such as pizza, sandwiches and hamburgers, rising to 11.2% of calories from 2.2%. Packaged sweet snacks and treats such as cakes and ice cream were a runner-up, which made up 12.9% of calorie consumption in 2018, compared with 10.6% in 1999.

When broken down by race and ethnicity, the growth in consumption of ultra-processed foods was significantly higher for Black, non-Hispanic youth, compared to white, non-Hispanic youths. The study also noted that Mexican American youths consumed ultra-processed foods at a persistently lower rate, which the researchers said may indicate more home cooking by Hispanic families.

Opinion: Why Ditching Processed Foods Won't Be Easy — Barriers To Cooking From Scratch

The study also found that the education levels of parents or family income didn't affect consumption of ultra-processed foods, suggesting that these types of foods are common in many households.

But the responsibility for tackling this problem shouldn't fall only on parents, Zhang says.

While she would encourage parents and children to consider "replacing ultra-processed foods with minimally and unprocessed foods," Zhang says changes at the policy level are needed "to achieve a broader and more sustainable impact."

Want Kids To Eat More Veggies? Market Them With Cartoons

Take, for instance, consumption of soda. The consumption of sugar-sweetened beverages dropped to 5.3% from 10.8% of overall calories. The study's researchers noted that the decline could be related to efforts such as soda taxes and raising awareness about the effects sugar has on youth health .

"We may have won this battle, at least partially, for some sugary beverages," Zhang says, "but we haven't yet against ultra-processed foods."

This widespread reliance on junk food is an increasing public health concern as the obesity rate has been rising steadily among U.S. youths for the past two decades.

While the study's authors said that the relationship between childhood obesity and ultra-processed foods is complex, they acknowledge that "cohort studies provide consistent evidence suggesting high intake of ultra-processed foods contributes to obesity in children and young adults."

Indeed, a 2019 study by researchers at the National Institutes of Health found that a diet filled with ultra-processed foods encourages people to overeat and gain weigh t compared to diets that consist of whole or minimally processed foods.

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Exposing the Dangers of Targeting Children as Consumers

July 03, 2024 • By The UCI Paul Merage School of Business

Over 50 years ago, studies were done to determine how advertising to children affected their consumption of junk food, cigarettes and alcohol. The results underscored the need to focus more research on the well-being of underage consumers and the influence of marketing on their physical, emotional and mental health.

In the decades since those early studies, academics have continued to explore the interaction between kids and marketing. Professor Connie Pechmann of the UCI Paul Merage School of Business, together with several colleagues from distinguished business schools across the country, has been studying the topic’s history to gain insights that may be useful to policy makers and others.

Pechmann joined Deborah Roedder John, professor of marketing at Carlson School of Management at the University of Minnesota, and Lan Nguyen Chaplin, professor of marketing at the Department of Integrated Marketing Communications, Northwestern University, in coediting a series of papers that provide an overview of the last 50 years of research on the consumer behavior of children. Their lead article, “Understanding the Past and Preparing for Tomorrow: Children and Adolescent Consumer Behavior Insights from Research in Our Field,” was published in April 2024 in the Journal of the Association for Consumer Research , the world’s largest global consumer research organization.

“We’ve been studying children and adolescent consumer behavior for 50 years,” says Pechmann. “The focus has always been on risks to their health and mental well-being. However, the target has changed over time. We started out with television advertising being the greatest risk, but now it’s moved toward social media, cannabis, vape and poverty.”

Overcoming Obstacles to Protect Children

As necessary as it is to understand how advertising negatively affects children, Pechmann says the research can be very difficult. “There isn’t a lot of research done on children because they’re such a protected group. You have to go through many more hurdles. Parents, of course, want to protect their children, and if the activities are illegal—like alcohol or cannabis—parents don’t want to reveal the information, so it makes it even harder.” The necessity of anonymity further limits the potential scope of research, because it prevents researchers from monitoring a subject’s progress over time.

Parents can be a source of complication as well. During interviews, parents can interfere with the process, which can reduce the accuracy of a child’s answers.

Such barriers haven’t stopped Pechmann and her coauthors from studying the consequences of advertising on children and their behaviors. “Everyone is very passionate about children,” she says. “We all started out as children. Many of us have children, so everyone is interested in protecting children and adolescents.”

To overcome the challenges associated with researching children and their consumer behaviors, Pechmann and her coauthors had to be creative. “Several of us arranged to go into schools, and we offered the schools something in return: drug education, for example,” she says. “In exchange for an hour of class time to collect data, we provided an additional class period of drug education to fill their state requirements. It’s not easy, but if you work hard, you can do it.”

Leveraging Government Surveys and Social Media

Some user data on children were available through social media and government surveys. “In Canada, the government decided to do a very large survey of children and adolescents on smoking,” says Pechmann. “California also does a healthy kids survey. Of course it’s anonymous, but they also go through schools, and they provide the data for free. Every once in a while, if we’re trying to reach really young children or children and their parents, we will work through a preschool or a nonprofit group that helps with parenting and very young children.”

Providing a Historical Overview of Childhood Research

In their article, Pechmann and her colleagues provide a historical overview of research on child consumers. “We start out looking at the ’70s and ’80s research on television advertising to children,” says Pechmann. “That was the main issue at the time. In the ’80s and ’90s we studied media literacy and how to teach children to become more savvy consumers. We also studied parenting behavior because parents have a huge influence on their kids. This led to a classification of parenting styles.”

It wasn’t until the mid-1990s through around 2010 that researchers started to look into children’s use of cigarettes and alcohol. “These products are illegal for children to use,” says Pechmann, “so we wanted to understand how they were using them and why. 2010 was also the year we started to study food because of rising childhood obesity rates, which has now spread globally.”

In 2020 research shifted to the effects of social media on children. “The average teenager spends eight and a half hours a day in front of a screen,” Pechmann says. “It’s frightening. Twenty-two percent of adolescent deaths in the United States are from suicide. We don’t always think about the mental health issues that result from these activities.”

In addition to social media consumption, researchers have also looked at how poverty shapes children. “One in six youth who are 17 or younger live in poverty in the United States,” says Pechmann. “That number is increasing, but we also need to talk about multiculturalism because that’s also increasing substantially. Until now, our focus has always been on white youth. We need to focus on Black and Brown children and the issues relevant to them.”

Exposing the Impact of Media and Advertising on Children

Pechmann is optimistic about the positive news coming from the research. “In 2004 the EU finally decided to ban advertising to children and adolescents,” she says. “That was something the United States tried to do in the ’70s and ’80s, but it didn’t succeed. There are some examples of successes, like when we see the smoking rate declined massively because there was so much attention on youth and smoking in the ’90s.”

Youth smoking was in decline until Juul came along with different flavors of vape. “Then it went back up again. Sometimes we close the door, and it opens back up, or it’s a slightly different door.”

The reason why this research is so important is that, up until age 18, young people are highly vulnerable to advertising. “There’s a lot of neuroscience that explains why adolescents and children are so vulnerable,” says Pechmann. “They’re much more attuned to rewards, much less attentive to consequences and risks, much more tolerant of ambiguity, much more sensitive to social cues and much more impulsive, so they don’t have a lot of cognitive control.” This is an advertiser’s dream, she says.

The Importance of Proper Parenting

While the research sometimes seems like it contains an abundance of dismal news, Pechmann wants to emphasize the silver lining. “We’ve learned a lot about what makes a good parent,” she says. “I’m not sure how easy it is to train parents, but we have extensive research that says the best parenting style is authoritative—not authoritarian where you boss [your children] around.”

Parents definitely need to set rules and boundaries, establish consequences, and set expectations so their children don’t make too many troubling choices, she says. “You have to be flexible. If you establish a punishment, it should be a reasonable punishment.”

Emphasizing the Value of Media Literacy

One positive takeaway from the research is the importance of media literacy. “We’ve made a lot of progress in this area because we now really understand how to teach that,” says Pechmann. “For example, California just passed a law that says they have to cover media literacy from elementary school through high school, and we know what to teach.”

Educational strategies must be adjusted for the student’s age, she says. “If someone is 7 or 8 years old, you can’t teach them the same thing as if they’re 17. When they’re 17, you can talk about tobacco companies targeting them. When they’re 7, you can teach them there’s such a thing as an ad that tries to persuade them to do something.” Yet, they have difficulty grasping that idea. “Let them know there’s an agenda behind the ad, and advertisers are likely to exaggerate the benefits. That’s where you start. There’s a lot of guidance here.”

One fascinating aspect of their research showed that the most effective deterrent to smoking, for example, was not to focus on the negative health effects but on social acceptability. “The Truth campaign made big gains against tobacco by saying smoking was socially unacceptable,” says Pechmann.

“That seems to be the way to go because young people don’t expect to live to be 70 years old. They think middle age is 30 or 40, so it doesn’t work to talk about the long-term health effects of smoking. The old anti-smoking and anti-drug messages were very much health-based: ‘Here’s your lung after smoking for years,’ and ‘here’s your brain on drugs.’ That approach has hopefully disappeared because it doesn’t work. Young people want immediate rewards, but they do not want immediate rejection from their friends for being uncool.”

How Persistence Pays Off

When it comes to advocating for children, Pechmann has learned persistence is key. “Today around 14 states have passed media literacy laws,” she says. “You have to be very persistent. If you just keep putting the articles out, and you keep sharing the data, it may take up to 50 years, but eventually we can start to legislate educational programs that benefit children and adolescents.”

The lesson here is to keep going, she says. “We can’t expect an immediate response. It’s taken 40 years, and we’re finally getting traction. The people who did the early research are about to retire, and it’s only now making a difference. That’s the lesson we have to learn as researchers. We are having an impact, but it might take a while.”

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The numbers are in: Junk food’s toll on physical & mental health

Consuming ultra-processed food, commonly known as junk food, has been associated with a higher risk of more than 30 different adverse mental and physical health outcomes, according to a new study. The research highlights the wide range of health issues that eating this kind of food can cause.

We’re often told that to maintain good health, we need to eat well, which includes a balanced diet low in ultra-processed foods (UPF), which includes packaged baked goods and snacks, sweetened, carbonated drinks, candy, sugary cereals, and ready-to-eat products.

While many of us are well aware of the health risks associated with eating a diet high in UPF, we might not appreciate just how harmful they can be. Researchers have pooled the data from 45 distinct meta-analysis studies associating UPF with adverse health outcomes, providing a high-level summary – an ‘umbrella review’ – of the evidence.

The total number of participants included across the umbrella review was close to 10 million. All meta-analyses were published in the last three years, and none were funded by companies that produce UPF. The researchers categorized the evidence as convincing, highly suggestive, suggestive, weak, or no evidence. They also assessed the quality of the evidence as high, moderate, low, or very low. Overall, the data showed that higher exposure to UPF was consistently associated with an increased risk of 32 adverse health outcomes that spanned mortality, cancer, and mental, respiratory, cardiovascular, gastrointestinal, and metabolic health outcomes.

Convincing evidence showed that higher consumption of UPF was associated with around a 50% increased risk of cardiovascular disease-related death, a 48% to 53% higher risk of anxiety and common mental health disorders, and a 12% higher risk of type 2 diabetes. Highly suggestive evidence indicated that higher UPF intake was associated with a 21% greater risk of death from any cause, a 40% to 66% increased risk of heart disease-related death, obesity, type 2 diabetes, and poor sleep, and a 22% increased risk of depression.

There was limited evidence associating UPF with asthma, gastrointestinal health, some cancers and cardiometabolic risk factors such as high blood fats and low levels of ‘good’ cholesterol.

The study has generated a great deal of interest from researchers and those in the medical community. Charlotte Gupta, a research fellow at the Appleton Institute, Central Queensland University, thought that the research provided “convincing evidence” but asked that we consider why some people eat UFP.

“[F]or some people, such as shiftworkers working at night … there is a lack of availability of fresh foods or time to prepare any food, and so ultra-processed foods have to be relied on,” Gupta said. “This highlights the need for not only individuals to try reducing ultra-processed foods in our diet but also for public health actions to improve access to healthier foods.”

Melanie McGrice, a practicing accredited dietician, said that the study’s results accorded with her professional experience.

“In my role as a dietitian, I see so many people reliant on ultra-processed food,” said McGrice. “Some of the key factors impacting consumption of ultra-processed foods include perceived convenience, social influences, emotional eating and advertising. I’ve seen extraordinary results for individuals who I have worked with as a result of decreasing intakes of ultra-processed foods.”

And Clare Collins, professor of nutrition and dietetics at the University of Newcastle and co-director of the Food and Nutrition Research Program at the Hunter Medical Research Institute, pointed out the issue with undertaking further interventional research.

“The studies are observational, which means cause and effect cannot be proven and that the research evidence gets downgraded, compared to intervention studies,” Collins said. “The problem is that it is not ethical to do an intervention study lasting for many years where you feed people lots of UPF every day and wait for them to get sick and die.”

The researchers acknowledge that their review cannot establish causation; that would require further research, specifically randomized controlled trials. Nonetheless, they say that their rigorous and systematic approach to evaluating the credibility and quality of the analyses they looked at suggests that the result would withstand scrutiny.

The study was published in The British Medical Journal .

Source: Scimex

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Science News Explores

Warning junk foods can harm a teen’s brain.

Though hard to resist, these foods pose risks to learning and mental health

Adolescent brains have a hard time resisting junk food. Researchers now are showing that high-fat and high-sugar diets — such as burgers, fries and sweets — can lead to disturbing changes in mental health.

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By Sharon Oosthoek

November 19, 2020 at 6:30 am

“You are what you eat.” When people say that, they mean a healthy diet can boost your health. But the opposite is also true. In fact, if you’re between the ages of 10 and 19, eating too much junk food can harm your body and your brain.

Junk food shapes adolescent brains in ways that impair their ability to think, learn and remember. It can also make it harder to control impulsive behaviors, says Amy Reichelt. It may even up a teen’s risk of depression and anxiety, she notes.

Reichelt is a brain and nutrition specialist at Canada’s Western University in London, Ontario. Adolescents are more sensitive than any other age group to foods with a lot of processed fat and sugar, she says. She is part of a group of scientists around the world who have been studying why.

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She and two other researchers at Western recently reviewed more than 100 studies (including their own) about how poor food choices can impact adolescent brains. They described what they learned in the May issue of  The Lancet Child and Adolescent Health .

One problem: Adolescent brains are not yet fully formed . And that actually leads to three problems in one, says Reichelt. First, adolescent brains are still developing the ability to assess risks and control actions. Second, teen brains get more pleasure than adult brains do from rewarding behaviors such as eating junk food. Third, adolescent brains can be more easily influenced by their environment. This can include any stress you’re feeling, any isolation or any drugs you may be taking. It can also be influenced by diet. Together, these all can combine to make junk food both hard to resist and extra bad for teen health.

Brains under construction

Let’s break that down, starting with preteen and teen behaviors. The brain region that tells us we shouldn’t eat chips all the time — and helps us resist that urge — is the last to mature. Called the prefrontal cortex, this region doesn’t fully develop until we are in our early 20s.

Brain imaging studies show that the prefrontal cortex turns on when we weigh risks and make decisions about how to act.

“Most of our complex brain functions happen in the prefrontal cortex,” says Reichelt. This includes complex math and reading. But she notes that it also includes “how to assess risky behavior.”

At the same time, teen brains get more buzz from rewards. Unlike the prefrontal cortex, the parts of the brain that make us feel good when we do something pleasurable — like eating tasty foods or being with friends — are fully developed by the teen years.

In fact, these regions are even more sensitive when we are young. That’s because of a natural chemical called dopamine (DOH-puh-meen). Dopamine is sometimes called the “feel good” chemical. It lifts our mood when we experience something rewarding. And it is especially active in adolescent brains.

As a neurotransmitter, it zips across the spaces between brain cells. Once it arrives at a new cell, dopamine binds to docking stations there. These molecules are known as receptors . When dopamine docks, those receptors relay the “feel good” signal from the last cell to this new one. That tells the brain that whatever it just experienced is worth getting more of. Adolescents have more dopamine receptors in the brain than do adults. So they get more good vibes from anything they find enjoyable.

The teen brain, thus, has two strikes against it when it comes to resisting junk food. “It has a heightened drive for rewards and reduced self-regulation,” says Reichelt.

That’s a big problem for adolescents because of the third issue: Growing brains can be more easily changed by eating high-fat, high-sugar foods. That’s what Reichelt and her team discovered in their studies of “teenage” mice.

Mouse brains on fat and sugar

Since mouse brains develop very much like our own, they can be used to understand how what we eat affects the human brain. In 2017, Reichelt was part of a team that fed adolescent mice high-fat foods to see how it affected their brains.

One group of mice ate a diet in which 63 percent of their calories came from fat. (That’s a lot of fat. It would be like eating bacon cheeseburgers and ice cream every day.) A second group ate a healthy diet.

As expected, mice eating high-fat food gained weight and put on body fat. But that was not all. These mice also performed worse on memory tests than did mice eating a normal diet.

The researchers tested the mice for what’s known as working memory. It’s the type that allows us to hold onto information long enough to use it. For example, working memory helps you remember which five things you need to buy at the store. Or what time you said you’d meet your friends. It’s also important for reasoning and decision-making. And it involves the prefrontal cortex — that’s the same brain area that helps make decisions.

Reichelt and her team used two different tests to gauge this working memory. In the first, they put the animals in a Y-shaped maze. Each mouse started in the center of the Y shape. From there they were free to explore two of the three arms of the maze. The third arm was blocked off.

Then the researchers opened up the maze’s third arm. Mice will naturally explore their environment and are drawn to new things. Given the chance, they should prefer to visit a new arm of the maze rather than one they’ve already explored. Or they would if they could remember which arms of the maze they had already visited.

Mice eating a healthy diet behaved as expected. They chose to explore the new arm of the maze. But those eating a high-fat diet did not prefer any one arm. The fact they explored all three at random seemed to show they could not remember which parts of the maze they had seen already.

The second test used a maze set up in a tank of murky water. The end of the maze is a platform just under the water’s surface. To get out of the water, a mouse must navigate to the platform by remembering landmarks. (The mice are scooped up to avoid drowning if they can’t find their way.)

Mice fed a healthy diet performed much better than did those eating high-fat chow. The fatter mice were just as good at swimming; they just did not find their way to the platform. This suggests they could not remember the landmarks.

Then the researchers looked at the animals’ brains. Here they found important differences in reelin, a chemical that helps brain cells chat with each other. Mice on high-fat chow had roughly 35 percent less reelin in their prefrontal cortex compared to mice on a healthy diet. The high-fat diet may have made the prefrontal cortex in these mice work less effectively.

People with brain diseases (such as schizophrenia and bipolar disorder) often have lower levels of reelin, too, says Reichelt. “We can’t blame that on junk food in adolescence,” she says. “But it may be a contributing factor [to risk of disease].”

Reichelt found similar behavioral effects in adolescent rats that got daily access to a sugary drink. They showed less desire to explore new things than did rats not fed sugar.

Each rat had been placed in an enclosed square area with different objects in each corner. The rats could explore all four objects. The researchers then removed the rats from the pen for five minutes and swapped the locations of two objects. Then each rat returned to the enclosure. Animals not fed sugar spent more time exploring objects that were now in a new place. This suggests they could tell the objects had been moved. But the sugar-fed rats spent just as much time with the unmoved objects as they did with the changed ones. It seems they couldn’t tell what had been moved.

Human brains on junk food

Other researchers have found links between brain health and what teenage kids eat. Felice Jacka is one of them. She is an expert in nutrition and psychiatry at Deakin University in Victoria, Australia.

In one 2013 study , she and her team recruited more than 2,000 11- to 14-year-olds living in London, England. Each answered questions about what they ate and how they felt, mentally. The kids were asked how many servings of fruits and vegetables they ate each day. They also were asked how often they ate chips, candy, cookies, fried foods and sugary soft drinks. Then they were sorted into five groups, depending on how healthy their diets were.

Next, the adolescents answered 13 questions designed to figure out if they suffered from depression. The questions asked about their emotions and behavior over the previous two weeks. They were phrased as statements. The kids described if those statements were true, not true or sometimes true. Questions ranged from “I feel miserable or unhappy” and “I didn’t enjoy anything at all” to “I felt so tired, I just sat around and did nothing.”

The researchers scored each kid’s answers for signs of depression. Adolescents who ate the most junk food were nearly 50 percent more likely to show signs of depression.

Why might eating junk food be linked to depression? The data are unclear. Some research suggests that processed foods, such as lunch meat, increases inflammation in the body and the brain. Inflammation is one of the body’s responses to cellular injury and involves swelling. Other research has linked inflammation with depression. In one study , researchers found that people with depression had 30 percent more brain inflammation than did people who were not depressed.

Good fat, bad fat

The good news is that you can make food choices that support a healthy brain.

“The brain is the most fat-rich organ we have,” notes Alexandra Richardson. She is an expert in how diet affects the brain and a researcher at the University of Oxford in England. “And where does it get its fats? From what we put in our bodies.”

But not all fats are the same. Our brains need a type known as omega-3 fats. These helpful fats are found in fish, flaxseed and some oils. These fats help build the membrane that surrounds brain cells. Brain cells need membranes to hold them together and to communicate well with each other.

In one 2005 study , Richardson and her team showed improved mental health in children who took omega-3 supplements. The 117 children who took part were between the ages of five and 12. All had problems with attention, hyperactivity and impulsivity. They also struggled with reading and spelling.

Over three months, about half the children took omega-3 pills. The others took look-alike pills with no fats. Such inactive “treatments” are known as placebos (Pluh-SEE-bohs). Compared to kids who got the placebo, those who took omega-3 pills showed improved attention and ability to control their hyperactive, impulsive behavior. Their reading and spelling scores also went up. This may have reflected being able to pay closer attention in class.

Junk food may trigger attention-related problems because it does not contain the good fats needed to build healthy brain cells, says Richardson. But downing foods with more good fats can support healthy brains.

Exercise for your brain

Research shows exercise can be a good way to fend off damage from junk food, notes Cassandra Lowe. She works at Western University, where together with Reichelt she has studied kids’ brain and nutrition.

Two important things happen in the brain when we exercise. The first is that the brain’s reward system — the one that feels good when we do something we like — becomes less sensitive to food cues. While scientists don’t quite know why, the outcome is a good thing. “We don’t find high-calorie foods as rewarding,” explains Lowe.

Exercise also triggers the body to make a protein called BDNF. That stands for brain-derived neurotrophic (Neur-oh-TROH-fik) factor. BDNF helps brain cells grow. It also strengthens links between them.

This means exercise can boost strong connections between the prefrontal cortex and other brain regions. When that happens, the prefrontal cortex “can exert control better,” says Lowe. In other words, better connections help us weigh risks, make informed decisions on how to act, and curb our impulses.

What is the take-home message for kids? Many already know that junk food can make people fat and physically unhealthy, says Richardson. Most don’t often understand that it also can lead to unhealthy brains.

Processed and fried foods, such as cold cuts, store-bought baked goods, candy and chips don’t have many of the nutrients our bodies and brains need, Richardson says. Kids need to understand that they tend to be rich both in calories and in “concoctions of chemicals that do not support human health — physical or mental.”

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What really makes junk food bad for us? Here’s what the science says

By Clare Wilson

9 June 2021

Fun, cheap and tasty, but perhaps not the healthiest option

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CUT down on fatty food. No, sugar. Aim for a Mediterranean diet. And remember to eat more plants…

The variability of healthy eating advice has become a cliché in itself. Yet despite all the contradictions, there is one thing that many agree on: we should avoid junk food. Until recently though, no one could give you a decent reason why. Gastronomic snobbery aside, science lacked an agreed definition of what junk food actually is, and that has made it difficult to know whether we should be avoiding it and, if so, why.

It has long been assumed that processed junk foods are bad because they tend to contain too much fat, salt and sugar. Recent studies, though, suggest that other mechanisms could be at work to make these foods harmful to our health. Getting to grips with what these are could help us not only make healthier choices, but also persuade the food industry to come up with healthier ways of giving us what we like to eat.

One thing’s for sure: we certainly do like it. Factory-made food makes up between 50 and 60 per cent of the average person’s calorie intake in the UK , and around 60 per cent in the US. But while junk food has a bad name among many food lovers, dietary health research and the public health advice that stems from it have so far concentrated either on individual food groups, like meat and dairy products, or the relative amounts of the three macronutrients – proteins, fats and carbohydrates – that we consume.…

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What Happens to Your Brain When You Eat Junk Food

Most of us know that junk food is unhealthy. We know that poor nutrition is related to heart problems, high blood pressure, and a host of other health ailments. You might even know that studies show that eating junk food has been linked to increases in depression .

But if it’s so bad for us, why do we keep doing it?

There is an answer. And the science behind it will surprise you.

Why We Crave Junk Food

Steven Witherly is a food scientist who has spent the last 20 years studying what makes certain foods more addictive (and tasty) than others. Much of the science that follows is from his excellent report, Why Humans Like Junk Food .

According to Witherly, when you eat tasty food, there are two factors that make the experience pleasurable.

First, there is the sensation of eating the food. This includes what it tastes like (salty, sweet, umami, etc.), what it smells like, and how it feels in your mouth. This last quality — known as “orosensation” — can be particularly important. Food companies will spend millions of dollars to discover the most satisfying level of crunch in a potato chip. Their scientists will test for the perfect amount of fizzle in a soda. These factors all combine to create the sensation that your brain associates with a particular food or drink.

The second factor is the actual macronutrient makeup of the food — the blend of proteins, fats, and carbohydrates that it contains. In the case of junk food, food manufacturers are looking for a perfect combination of salt, sugar, and fat that excites your brain and gets you coming back for more.

Here’s how they do it…

How Science Creates Cravings

There are a range of factors that scientists and food manufacturers use to make food more addictive.

Dynamic contrast. Dynamic contrast refers to a combination of different sensations in the same food. In the words of Witherly, foods with dynamic contrast have “an edible shell that goes crunch followed by something soft or creamy and full of taste-active compounds. This rule applies to a variety of our favorite food structures — the caramelized top of a creme brulee, a slice of pizza, or an Oreo cookie — the brain finds crunching through something like this very novel and thrilling.”

Salivary response. Salivation is part of the experience of eating food and the more that a food causes you to salivate, the more it will swim throughout your mouth and cover your taste buds. For example, emulsified foods like butter, chocolate, salad dressing, ice cream, and mayonnaise promote a salivary response that helps to lather your taste buds with goodness. This is one reason why many people enjoy foods that have sauces or glazes on them. The result is that foods that promote salivation do a happy little tap dance on your brain and taste better than ones that don’t.

Rapid food meltdown and vanishing caloric density. Foods that rapidly vanish or “melt in your mouth” signal to your brain that you’re not eating as much as you actually are. In other words, these foods literally tell your brain that you’re not full, even though you’re eating a lot of calories.

The result: you tend to overeat.

In his best-selling book, Salt Sugar Fat ( audiobook ), author Michael Moss describes a conversation with Witherly that explains vanishing caloric density perfectly…

I brought him two shopping bags filled with a variety of chips to taste. He zeroed right in on the Cheetos. “This,” Witherly said, “is one of the most marvelously constructed foods on the planet, in terms of pure pleasure.” He ticked off a dozen attributes of the Cheetos that make the brain say more. But the one he focused on most was the puff’s uncanny ability to melt in the mouth. “It’s called vanishing caloric density,” Witherly said. “If something melts down quickly, your brain thinks that there’s no calories in it . . . you can just keep eating it forever.”

Sensory specific response. Your brain likes variety. When it comes to food, if you experience the same taste over and over again, then you start to get less pleasure from it. In other words, the sensitivity of that specific sensor will decrease over time. This can happen in just minutes.

Junk foods, however, are designed to avoid this sensory specific response. They provide enough taste to be interesting (your brain doesn’t get tired of eating them), but it’s not so stimulating that your sensory response is dulled. This is why you can swallow an entire bag of potato chips and still be ready to eat another. To your brain, the crunch and sensation of eating Doritos is novel and interesting every time.

Calorie density. Junk foods are designed to convince your brain that it is getting nutrition, but to not fill you up. Receptors in your mouth and stomach tell your brain about the mixture of proteins, fats, carbohydrates in a particular food, and how filling that food is for your body. Junk food provides just enough calories that your brain says, “Yes, this will give you some energy” but not so many calories that you think “That’s enough, I’m full.” The result is that you crave the food to begin with, but it takes quite some time to feel full from it.

Memories of past eating experiences. This is where the psychobiology of junk food really works against you. When you eat something tasty (say, a bag of potato chips), your brain registers that feeling. The next time you see that food, smell that food, or even read about that food, your brain starts to trigger the memories and responses that came when you ate it. These memories can actually cause physical responses like salivation and create the “mouth-watering” craving that you get when thinking about your favorite foods.

All of this brings us to the most important question of all.

Food companies are spending millions of dollars to design foods with addictive sensations. What can you and I do about it? Is there any way to counteract the money, the science, and the advertising behind the junk food industry?

How to Kick the Junk Food Habit and Eat Healthy

The good news is that the research shows that the less junk food you eat, the less you crave it. My own experiences have mirrored this. As I’ve slowly begun to eat healthier, I’ve noticed myself wanting pizza and candy and ice cream less and less. Some people refer to this transition period as “gene reprogramming.”

Whatever you want to call it, the lesson is the same: if you can find ways to gradually eat healthier, you’ll start to experience the cravings of junk food less and less. I’ve never claimed to have all the answers (or any, really), but here are three strategies that might help.

1. Use the “outer ring” strategy and the “5 ingredient rule” to buy healthier food.

The best course of action is to avoid buying processed and packaged foods. If you don’t own it, you can’t eat it. Furthermore, if you don’t think about it, you can’t be lured by it.

We’ve talked about the power of junk food to pull you in and how memories of tasty food in the past can cause you to crave more of it in the future. Obviously, you can’t prevent yourself from ever thinking about junk food, but there are ways to reduce your cravings.

First, you can use my “outer ring” strategy to avoid processed and packaged foods at the grocery store. If you limit yourself to purchasing foods that are on the outer ring of the store, then you will generally buy whole foods (fruits, vegetables, meat, eggs, etc.). Not everything on the outer ring is healthy, but you will avoid a lot of unhealthy foods.

You can also follow the “5 ingredient rule” when buying foods at the store. If something has more than 5 ingredients in it, don’t buy it. Odds are, it has been designed to fool you into eating more of it. Avoid those products and stick with the more natural options.

2. Eat a variety of foods.

As we covered earlier, the brain craves novelty.

While you may not be able to replicate the crunchy/creamy contrast of an Oreo, you can vary your diet enough to keep things interesting. For example, you could dip a carrot (crunchy) in some hummus (creamy) and get a novel sensation. Similarly, finding ways to add new spices and flavors to your dishes can make eating healthy foods a more desirable experience.

Moral of the story: eating healthy doesn’t have to be bland. Mix up your foods to get different sensations and you may find it easier than eating the same foods over and over again. (At some point, however, you may have to fall in love with boredom .)

3. Find a better way to deal with your stress.

There’s a reason why many people eat as a way to cope with stress. Stress causes certain regions of the brain to release chemicals (specifically, opiates and neuropeptide Y). These chemicals can trigger mechanisms that are similar to the cravings you get from fat and sugar. In other words, when you get stressed, your brain feels the addictive call of fat and sugar and you’re pulled back to junk food.

We all have stressful situations that arise in our lives. Learning to deal with stress in a different way can help you overcome the addictive pull of junk food. This could include simple breathing techniques or a short guided meditation . Or something more physical like exercise or making art .

With that said, if you’re looking for a better written and more detailed analysis of the science of junk food, I recommend reading the #1 New York Times best-seller, Salt Sugar Fat ( audiobook ).

Where to Go From Here

One of my goals with this article is to reveal just how complex poor eating habits can be. Junk food is designed to keep you coming back for more. Telling people that they “need more willpower” or should “just stop eating crap” is short-sighted at best.

Thanks for reading. You can get more actionable ideas in my popular email newsletter. Each week, I share 3 short ideas from me, 2 quotes from others, and 1 question to think about. Over 3,000,000 people subscribe . Enter your email now and join us.

James Clear writes about habits, decision making, and continuous improvement. He is the author of the #1 New York Times bestseller, Atomic Habits . The book has sold over 20 million copies worldwide and has been translated into more than 60 languages.

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News Release

Thursday, May 16, 2019

NIH study finds heavily processed foods cause overeating and weight gain

Small-scale trial is the first randomized, controlled research of its kind.

People eating ultra-processed foods ate more calories and gained more weight than when they ate a minimally processed diet, according to results from a National Institutes of Health study. The difference occurred even though meals provided to the volunteers in both the ultra-processed and minimally processed diets had the same number of calories and macronutrients. The results were published in Cell Metabolism .

This small-scale study of 20 adult volunteers, conducted by researchers at the NIH’s National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), is the first randomized controlled trial examining the effects of ultra-processed foods as defined by the NOVA classification system . This system considers foods “ultra-processed” if they have ingredients predominantly found in industrial food manufacturing, such as hydrogenated oils, high-fructose corn syrup, flavoring agents, and emulsifiers.

Previous observational studies looking at large groups of people had shown associations between diets high in processed foods and health problems. But, because none of the past studies randomly assigned people to eat specific foods and then measured the results, scientists could not say for sure whether the processed foods were a problem on their own, or whether people eating them had health problems for other reasons, such as a lack of access to fresh foods.

“Though we examined a small group, results from this tightly controlled experiment showed a clear and consistent difference between the two diets,” said Kevin D. Hall, Ph.D., an NIDDK senior investigator and the study’s lead author. “This is the first study to demonstrate causality — that ultra-processed foods cause people to eat too many calories and gain weight.”

For the study, researchers admitted 20 healthy adult volunteers, 10 male and 10 female, to the NIH Clinical Center for one continuous month and, in random order for two weeks on each diet, provided them with meals made up of ultra-processed foods or meals of minimally processed foods. For example, an ultra-processed breakfast might consist of a bagel with cream cheese and turkey bacon, while the unprocessed breakfast was oatmeal with bananas, walnuts, and skim milk.

The ultra-processed and unprocessed meals had the same amounts of calories, sugars, fiber, fat, and carbohydrates, and participants could eat as much or as little as they wanted.

On the ultra-processed diet, people ate about 500 calories more per day than they did on the unprocessed diet. They also ate faster on the ultra-processed diet and gained weight, whereas they lost weight on the unprocessed diet. Participants, on average, gained 0.9 kilograms, or 2 pounds, while they were on the ultra-processed diet and lost an equivalent amount on the unprocessed diet.

“We need to figure out what specific aspect of the ultra-processed foods affected people’s eating behavior and led them to gain weight,” Hall said. “The next step is to design similar studies with a reformulated ultra-processed diet to see if the changes can make the diet effect on calorie intake and body weight disappear.”

For example, slight differences in protein levels between the ultra-processed and unprocessed diets in this study could potentially explain as much as half the difference in calorie intake.

“Over time, extra calories add up, and that extra weight can lead to serious health conditions,” said NIDDK Director Griffin P. Rodgers, M.D. “Research like this is an important part of understanding the role of nutrition in health and may also help people identify foods that are both nutritious and accessible — helping people stay healthy for the long term.”

While the study reinforces the benefits of unprocessed foods, researchers note that ultra-processed foods can be difficult to restrict. “We have to be mindful that it takes more time and more money to prepare less-processed foods,” Hall said. “Just telling people to eat healthier may not be effective for some people without improved access to healthy foods.”

Support for the study primarily came from the NIDDK Division of Intramural Research.

About the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK): The NIDDK, a component of the National Institutes of Health (NIH), conducts and supports research on diabetes and other endocrine and metabolic diseases; digestive diseases, nutrition and obesity; and kidney, urologic and hematologic diseases. Spanning the full spectrum of medicine and afflicting people of all ages and ethnic groups, these diseases encompass some of the most common, severe, and disabling conditions affecting Americans. For more information about the NIDDK and its programs, see https://www.niddk.nih.gov .

About the National Institutes of Health (NIH): NIH, the nation's medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov .

NIH…Turning Discovery Into Health ®

Hall KD, et al. Ultra-processed diets cause excess calorie intake and weight gain: A one-month inpatient randomized controlled trial of ad libitum food intake. Cell Metabolism . May 16, 2019.

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From banning junk food ads to a sugar tax: With diabetes on the rise, Australia can't afford to ignore the evidence

by Gary Sacks, The Conversation

There are renewed calls this week for the Australian government to implement a range of measures aimed at improving our diets. These include restrictions on junk food advertising, improvements to food labeling, and a levy on sugary drinks.

This time the recommendations come from a parliamentary inquiry into diabetes in Australia. Its final report , tabled in parliament on Wednesday, was prepared by a parliamentary committee comprising members from across the political spectrum.

The release of this report could be an indication that Australia is finally going to implement the evidence-based healthy eating policies public health experts have been recommending for years.

But we know Australian governments have historically been unwilling to introduce policies the powerful food industry opposes. The question is whether the current government will put the health of Australians above the profits of companies selling unhealthy food.

Diabetes in Australia

Diabetes is one of the fastest growing chronic health conditions in the nation, with more than 1.3 million people affected . Projections show the number of Australians diagnosed with the condition is set to rise rapidly in coming decades.

Type 2 diabetes accounts for the vast majority of cases of diabetes. It's largely preventable, with obesity among the strongest risk factors.

This latest report makes it clear we need an urgent focus on obesity prevention to reduce the burden of diabetes. Type 2 diabetes and obesity cost the Australian economy billions of dollars each year and preventive solutions are highly cost-effective .

This means the money spent on preventing obesity and diabetes would save the government huge amounts in health care costs . Prevention is also essential to avoid our health systems being overwhelmed in the future.

What does the report recommend?

The report puts forward 23 recommendations for addressing diabetes and obesity. These include:

• restrictions on the marketing of unhealthy foods to children, including on TV and online
• improvements to food labeling that would make it easier for people to understand products' added sugar content
• a levy on sugary drinks, where products with higher sugar content would be taxed at a higher rate (commonly called a sugar tax).

These key recommendations echo those prioritized in a range of reports on obesity prevention over the past decade. There's compelling evidence they're likely to work.

Restrictions on unhealthy food marketing

There was universal support from the committee for the government to consider regulating marketing of unhealthy food to children.

Public health groups have consistently called for comprehensive mandatory legislation to protect children from exposure to marketing of unhealthy foods and related brands.

An increasing number of countries, including Chile and the United Kingdom , have legislated unhealthy food marketing restrictions across a range of settings including on TV, online and in supermarkets. There's evidence comprehensive policies like these are having positive results.

In Australia, the food industry has made voluntary commitments to reduce some unhealthy food ads directly targeting children. But these promises are widely viewed as ineffective .

The government is currently conducting a feasibility study on additional options to limit unhealthy food marketing to children.

But the effectiveness of any new policies will depend on how comprehensive they are. Food companies are likely to rapidly shift their marketing techniques to maximize their impact. If any new government restrictions do not include all marketing channels (such as TV, online and on packaging) and techniques (including both product and brand marketing), they're likely to fail to adequately protect children.

Food labeling

Food regulatory authorities are currently considering a range of improvements to food labeling in Australia.

For example, food ministers in Australia and New Zealand are soon set to consider mandating the health star rating front-of-pack labeling scheme.

Public health groups have consistently recommended mandatory implementation of health star ratings as a priority for improving Australian diets. Such changes are likely to result in meaningful improvements to the healthiness of what we eat.

Regulators are also reviewing potential changes to how added sugar is labeled on product packages. The recommendation from the committee to include added sugar labeling on the front of product packaging is likely to support this ongoing work.

But changes to food labeling laws are notoriously slow in Australia. And food companies are known to oppose and delay any policy changes that might hurt their profits.

A sugary drinks tax

Of the report's 23 recommendations, the sugary drinks levy was the only one that wasn't universally supported by the committee. The four Liberal and National party members of the committee opposed implementation of this policy.

As part of their rationale, the dissenting members cited submissions from food industry groups that argued against the measure. This follows a long history of the Liberal party siding with the sugary drinks industry to oppose a levy on their products.

The dissenting members didn't acknowledge the strong evidence that a sugary drinks levy has worked as intended in a wide range of countries.

In the UK, for example, a levy on sugary drinks implemented in 2018 has successfully lowered the sugar content in UK soft drinks and reduced sugar consumption .

The dissenting committee members argued a sugary drinks levy would hurt families on lower incomes. But previous Australian modeling has shown the two most disadvantaged quintiles would reap the greatest health benefits from such a levy, and accrue the highest savings in health-care costs.

What happens now?

Improvements to population diets and prevention of obesity will require a comprehensive and coordinated package of policy reforms.

Globally, a range of countries facing rising epidemics of obesity and diabetes are starting to take such strong preventive action.

In Australia, after years of inaction, this week's report is the latest sign that long-awaited policy change may be near.

But meaningful and effective policy change will require politicians to listen to the public health evidence rather than the protestations of food companies concerned about their bottom line.

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• Coffee House

Vegans are addicted to junk food

Which is ironic, given how moralistic they are.

• 8 July 2024, 5:01am
• From Spectator Life

Julie Bindel

Recent research has revealed what many of us suspected: that fake meat is highly processed and contains junk such as exotic emulsifiers, stabilisers, flavour enhancers and artificial colourings, all of which are designed to make them feel, taste and look like the real thing. Often, they are loaded with salt, sugar and fat. Many Britons become vegan (or vegetarian) precisely because they want to cut down on this stuff, but end up with even higher blood pressure and blood sugar levels.

Lots of my friends’ offspring are vegan for ‘save the planet’ reasons – but they subsist on chips, cola, and fake burgers, not even realising that avocado farming is killing off the rainforest. Facon (‘This isn’t Bacon!’ – no kidding!), chickin and cheeze substitutes are hellish. Meat-substitute nuggets, given to kids by hessian-clad parents, are packed with rubbish.

As a feminist born in 1962, I have been surrounded by vegetarians (and, in more recent decades, vegans), throughout my adult life. While it is both a lefty position and a stereotypical, Greenham Common type ‘women save the planet’ thing – it is also an anti-machismo schtick. One book published in 1990, The Sexual Politics of Meat: A Feminist-Vegan Critical Theory , by Carol J. Adams, argued that behind every forkful of meat is the death of an animal, and that this cloaks the violence inherent to meat-eating, ‘to protect the conscience of the meat eater and render the idea of individual animals as immaterial to everyone’s selfish desires.’

I got it, but I didn’t buy it. I figured that I was doing enough to make the world a better place, campaigning to end male violence against women and girls. I would occasionally join forces with the animal liberationists by joining their protests outside fur coat shops, in exchange for their attendance at protests outside local porn cinemas or strip joints.

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Alexander larman, has america had enough of prince harry.

But the main issue for me was that the fake meat and dairy products that were becoming popular by the late 1980s tasted like cardboard with the flavour extracted. The local health food store (staffed by humourless, overly earnest activists) would sell blocks of fake cheese that looked like stuff for grouting bathrooms, and jars of cashew nut butter that needed a drill and a hardhat to get into.

Today, while actual junk food is looked down upon because it is eaten by the working classes, vegan junk food is extremely popular. Everyone knows a diet of sweet, carbonated drinks, chips, and processed food is bad, and parents that take their kids to McDonald’s for a treat are considered slightly more dangerous than Fred and Rosemary West. Queuing in a fish and chip shop recently, I heard a middle-class couple (out for what they described as their ‘special fortnightly treat’), saying that a woman, who came in at least twice a week to feed her kids, was nothing short of a child abuser and should be reported to social services forthwith. One of them remarked, ‘Can’t she cook soup from scratch?’

Of course, it’s a different matter when upper–middle–class posers eat vegan junk food, which is somehow seen as very on-message and not unhealthy at all. But why on earth would it be? Think about vegan sausage rolls (stuffed with oil, salt, and sugar), cakes without dairy that need twice as much sweetener to mask the horrible cotton wool taste, and dreadful vegan ‘cheese’, packed with something I really don’t want to know about.

The flavour of these products is indistinguishable from that of really cheap, nasty meat, packed with additives and fillers. As soon as I could afford to, I stopped buying factory-farmed animals, cut down my consumption of meat, and only bought free range. It tastes better, and allows me a clear conscience. If anybody suggests jackfruit – with its lack of flavour and weird texture – as a meat substitute, I tell them I’d rather eat a tomato salad. And the ‘smashed avocado on sourdough’ craze, which has ruined high street cafés, has also contributed to deforestation and degradation in central and southern Mexican forests.

But never let it be said that I’m resistant to innovation. Two or three years ago, I was introduced to oat milk by a friend who doesn’t like the taste of dairy. She challenged me to try it, and I was sold. I haven’t had cow’s milk since. Occasional junk food is fine, but if you are going to become vegan, at least learn to cook. I can recommend some divine South Indian recipes. Give me a cauliflower and coconut curry over a tasteless soy burger any day.

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• Front Psychol

How Do Perceived Health Threats Affect the Junk Food Eating Behavior and Consequent Obesity? Moderating Role of Product Knowledge Hiding

Associated data.

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author.

The predominant use of junk food in our societies is continuously held responsible for the obese body physiques and overweight among the kids and adolescents. The current supportive environments where organic foods are limited, and new processed foods have been brought to the market with more variant tastes and acceptability for the kids and adolescents that have diverged their eating patterns. It has significantly contributed to the health issues and growth discrepancies of the users. However, the awareness of the food contents is an important milestone for understanding the risks associated with the usage of junk foods. A quantitative approach has been used in this study to measure the effect of perceived severity, vulnerability and fear on the junk food eating behaviors and ultimately on the obesity. The moderating role of product knowledge hiding has also been measured on the relationship of junk food eating and obesity. Structural equation modeling is used using the software Smart-PLS for measuring the hypothesis with a sample size of 228 selected through purposive sampling. The sample consisted of kids and adolescents who were reached on purpose for data collection. The current study has explored the role of perceived severity, vulnerability and the fear of using junk foods which have been found as a negative effect on junk food eating behavior which is positively associated with obesity among the kids and adolescents. The result of study shows that perceived threat has a negative effect on the junk food eating behavior of the adolescents. However, the positive relationship of junk food eating behavior with obesity can be decreased if the information about the products is not hidden. This study will be useful for making the consumers aware of the product knowledge hiding of the junk food usage. Moreover, it will help the users in creating understanding of risks allied with the use of junk food which may be addressed in order to avoid obesity issues in the kids and adolescents globally.

Introduction

Although there is a growing public interest in health, the rising incidence of diet-related non-communicable disorders, such as obesity, can still be seen. Obesity treatment interventions have had relatively limited impacts over time, especially in high-risk groups ( Stice et al., 2006 ). While interventions to minimize sedentary habits, notably television consumption or spending time watching television, have been more successful, studies show that a greater knowledge of healthy eating determinants is needed to enhance the prevalence of positive health behaviors, particularly in at-risk populations like teenagers ( Leme et al., 2016 ; Mc Morrow et al., 2017 ). An unhealthy diet, defined as a high sugar and fat intake with a low intake of fruits and vegetables, is one of the primary causes of non-communicable illness worldwide and is closely linked to early death. Poor food habits are a major contributor to the obesity pandemic ( Loef and Walach, 2012 ; Matthews et al., 2016 ). The relevance of health and nutrition to one’s Self-Perception may have a significant impact on one’s actions. To assess its influence on eating patterns, other terminology has been employed, such as health interests ( Tromp et al., 2005 ; Sun, 2008 ). These conceptual frameworks, regardless of nomenclature, emphasize the significance of worries about health, food, and nutrition.

A lot of research has gone into assessing consumer perceptions of food dangers, and the number of such studies has risen in recent decades for a variety of reasons. Highly processed foods, for example, have been widely introduced to the market, but food has also been implicated in several food crises ( Leikas et al., 2009 ; Martinez-Poveda et al., 2009 ). Risks and issues related to one’s individual lifestyle are frequently overlooked in comparison to societal risks ( Nawaz et al., 2020b ). Because most individuals believe they have control over their eating habits, perceived health and nutrition hazards may have little influence on their eating habits. However, it appears that among pre- and reproductive-age females, reported concerns about food and health are of greater relevance than among other groups. To begin with, eating habits formed as a youngster may not only follow a woman into adulthood but may also be handed on to her off-spring ( Mikkilä et al., 2005 ; Palfreyman et al., 2014 ). Second, effective preventative programs for changing the diet of young females (and, by extension, their children) are still required to boost their nutritional status and, as a result, to lower obesity and malnutrition rates ( Mikkilä et al., 2005 ; Palfreyman et al., 2014 ).

Dissection of perceived health threats result into perceived severity, perceived vulnerability, and fear. These perceptional threats are of the same concern regarding junk food eating behaviors leading to obesity. The adverse repercussions that a person identifies with an event or outcome, such as a cancer diagnosis, are referred to as perceived severity (also defined as the perceived seriousness). These implications might be related to a future occurrence or a present situation, such as a pre-existing health problem. Although perceived severity is a type of negative value and unfavorable polarity, the word appears to get its origins in the Health Belief Model (HBM). The paradigm is based on psychological research and Lewin’s behavioral motivation theory ( Luger, 2013 ). According to Burnes (2019) , behavior is determined by two factors: (1) what importance a person places on a certain result, and (2) actual possibility that an individual will succeed in reaching their goal. The key components of ‘expectancy-value’ theories are these two aspects together.

The HBM was created to better understand how preventative and early detection practices are adopted. The paradigm claims that illness severity and perceived vulnerability to disease combine to generate a ‘threat,’ and that threat perception motivates action. According to the paradigm, threat perception drives behavior. Furthermore, signs to action were considered as important to set the process in motion, such as the appearance of symptoms or having a medical appointment ( Steckler et al., 2010 ). Perceived severity could have been utilized as an indicator of obesity due to eating unhealthy junk food. Perceived vulnerability, also known as perceived susceptibility, perceived likelihood, and perceived probability, refers to a person’s perception of the possibility of health hazard or the development of health condition ( Gochman and Saucier, 1982 ).

Perceived vulnerability is an integral component of a threat evaluation process, according to Protection Motivation Theory, implying that people actively participate in assessing their risk. The Precaution Adoption Process greatly broadened the construct by proposing that people go through multiple phases of identifying their vulnerability, ranging from not being aware of the danger to being aware of the threat to eventually admitting that they are personally at risk. Perceived vulnerability could help in defining danger of obesity associated with eating unhealthy or junk foods ( Magallares et al., 2015 ) so, it could lead to be an integral part of our research model.

Fear is also an important factor in eating healthy or unhealthy food which could lead to obesity. When a person is confronted with a threat, they may get fearful. Fear has been linked to increased arousal, negative or unpleasant subjective experiences, and a distinctive facial expression that includes wider eyes and an open mouth. Fearful stimuli have been shown to improve visual perception in studies. In an array of distracter pictures, fear-inducing stimuli are found faster than fear-irrelevant stimuli ( Öhman et al., 2001 ). One of the roles of fear, according to evolutionary perspectives on emotions, is to improve perception ( Susskind et al., 2008 ). This kind of fear has played a significant role in determining the health-related habits. This could also lead to behaviors related to eating healthy or unhealthy junk food leading to obesity.

The prevalence of bad eating habits has been connected to the adoption of a western lifestyle by individuals in emerging countries. A lack of consistency in eating breakfast, a low frequency of fruit and vegetable intake, a proclivity toward increased junk food consumption, and a high frequency of soft drink use are all examples of harmful dietary patterns. Breakfast consumption contributes to positive changes in the hormonal, and neurological processes that regulate intake of food, whereas missing breakfast leads to obesity. Vegetables and fruit, on the other hand, are high in water and fiber and have a low energy density. As a result of the satiating impact of fiber, they defend against obesity by resulting in fewer calories ingested and the displacement of energy-dense meals ( Howarth et al., 2001 ; Rolls et al., 2004 ; Leidy et al., 2013 ). Junk food and soft drinks, on the other hand, are high in energy and contain empty calories, which contribute to obesity ( Hao et al., 2020 ). Resultantly, shifting dietary habits, which include increasing intake of more energy-dense foods and decreasing consumption of less energy-dense foods, may be inflicting double damage ( Nawaz et al., 2020a ).

According to the existing research on knowledge sharing, managers who share their information have beneficial effects on personal productivity and individual job performance, team creativity and innovation, and organizational financial performance. Although information concealing and other comparable notions, such as knowledge sharing and knowledge hoarding, are said to have some similarities or overlap, knowledge hiding differs from these ideas in at least two respects ( Dong et al., 2016 ). Although no research in so far has been conducted on knowledge hiding about products but there is a scope of finding the role of product knowledge hiding on different health behaviors and the consequences of those behavior. So, moderating role of product knowledge hiding was suggested in our study context.

Dietary behavior is changing dramatically on a global scale, and it is connected to the “New World Syndrome,” in which emerging nations change their habits and lifestyles to a junk food-based sedentary lifestyle, often in slavish imitation of the West, and fast-food firms’ relentless marketing. Obesity has been recognized as one of the first waves of this New World Syndrome, followed by a slew of chronic ailments that are wreaking havoc on emerging nations’ socioeconomic and public health systems ( Magallares et al., 2015 ). These have now reached worldwide epidemic proportions and should be considered today’s most pressing public health issue. These things produce several research questions such as how perceived health threats could lead to obesity? how junk food eating behavior could mediate the relationship of perceived health threats with obesity? What regulations product knowledge hiding could impose on the mediating relationship of junk food eating behavior with obesity. To address these questions, following research was designed to analyze the impact of perceived health threats such as perceived severity, perceived vulnerability and fear on obesity, evaluate the mediating role of junk food eating behavior between the relationship of perceived health threats with obesity and exploring the moderating role of product knowledge hiding between mediating junk food eating behavior and obesity problems.

Review of Literature and Hypotheses Development

The factors of perception regarding eating unhealthy or junk food leading to obesity are based on some theories of expectancy value. Such a theory which provided basis for devising the relationships of perceived vulnerability, perceived severity and fear of eating junk food habits leading to obesity is explained below.

Protection Motivation Theory

The PMT model was created to explain how fear appeals affect health attitudes and behaviors ( Rogers, 1975 ). Fear-inducing communications have a significant influence on behavior selection. Improvements in the perceived level of fear frequently led to increases in acceptability of the adaptive control action or intention, according to a meta-analysis of studies of fear-arousing messages published between 1953 and 1980 ( Sutton and Hallett, 1988 ). Increases in perceived response efficacy also enhanced the likelihood of choosing the ability to respond. Theory has been used to a varied range of themes, including areas of interest outside health-related difficulties, according to a detailed narrative assessment of the literature and research on theory ( Prentice-Dunn et al., 1997 ). Theory has been expanded to environmental concerns, prevention of accidents, safeguarding others, and political issues in addition to health promotion and illness prevention.

Protection motivation theory is a commonly used paradigm for understanding how people react to stimuli that alert them to a possible hazard. Such stimuli include fear signals that allow people to take precautions or avoid from taking actions that could damage them or others. This idea belongs to the category of expectation value theories, which claim that certain attitudes or beliefs will lead to specific behaviors. People discuss possible responses through a threat better coping evaluation process. The threat evaluation method includes determining the danger’s severity as well as the possibility (or vulnerability) of the threat occurring. The efficacy of the reaction, the difficulty of enacting the response, and the perceived Self-Efficacy of executing the coping response are all factors considered throughout the coping assessment process. When the danger appraisal outweighs the coping appraisal, the result is a maladaptive reaction ( Shillair, 2020 ).

Rogers examined the literature on theory and discovered that theory and its elements were well supported. Their finding, however, was predicated on a narrative examination. The degree of the influence of the protection motivation theory aspects might be assessed with a better quantitative grasp of the model variables. Fear is assessed in PMT to forecast and motivate protective responses, as well as to explain the cognitive processes involved in danger and coping assessments ( Sadeghi et al., 2019 ). Threat and coping assessments can result in adaptive or maladaptive reactions, both of which represent health risks ( Rogers, 1975 ). The following elements influence threat evaluation in PMT: (1) perceived severity, (2) perceived vulnerability, and (3) perceived benefits. As a result, there is a larger motivation for engaging in health-promoting actions when the perceived severity and vulnerability are high and the perceived benefits are low. Fear is a mediator between perceived vulnerability, severity, and threat evaluation in general.

Resultantly, if someone feels susceptible to a major health hazard, their anxiety level rises, and they are more driven to engage in preventive/protective action ( Sadique et al., 2007 ; Watkins et al., 2007 ; Sharifirad et al., 2014 ; Ling et al., 2019 ). To establish protective motivation, coping and threat evaluation processes are combined. It is suggested that PMT may properly predict whether or not protective behaviors would be adopted ( Lowe et al., 2000 ; Jiang et al., 2009 ; Zare Sakhvidi et al., 2015 ; Babazadeh et al., 2017 ). PMT has been used to explore a variety of behaviors, including influenza vaccine injection, H1N1 pandemic prevention, cancer prevention and sun protection behaviors, SARS prevention behaviors, and communicable diseases and skin cancer prevention behaviors ( Ezati Rad et al., 2021 ). Based on this theory and its components, our research was designed for analysis of perceived severity, perceived vulnerability, and fear about eating junk food leading to obesity.

Relationship of Perceived Health Threats With Junk Food Eating Behavior

Changing a behavior, adopting a protective behavior, or doing both. One can adopt a new behavior, change an old one, or participate in behaviors that blend new and modified features while altering behavior ( Rosenstock, 1974 ; Witte and Allen, 2000 ). Danger assessments are based on one’s impression of the threat’s severity as well as one’s vulnerability to the threat. The severity of a threat is determined by severity, but vulnerability is determined by the likelihood of being in danger ( Neuwirth et al., 2000 ; Umeh, 2003 ; McMath and Prentice-Dunn, 2005 ). A person is more likely to adjust to a situation when they have a strong conviction in the threat’s seriousness and personal vulnerability. Information that is potentially dangerous might originate from a variety of places, including previous experiences ( Umeh, 2004 ). Prior correlation research addressing the association between perceived danger and healthy eating behavior have frequently recruited certain at-risk populations, such as those who are more susceptible to memory loss and cardiovascular disease ( Cox et al., 2004 ; McKinley, 2009 ). Given that obesity has surpassed cigarette smoking and alcohol consumption as the leading cause of death in the United States, the threat of obesity is likely to enter the minds of a much larger populace.

Furthermore, earlier research that used threat measures to explain eating behavior did not look at fruit and vegetable consumption. Different studies have frequently assessed harmful fat intake without additionally examining fruit and vegetable intake. People are often presented with several options when determining what meals to eat, and models should account for these decisions ( Baranowski et al., 2003 ). Only assessing the desire to eat harmful fat items yielded inconsistent findings, especially in terms of severity and susceptibility. In Australia, for example, a community at risk for cardiovascular disease was studied. Reaction efficacy (conceptions of a suggested initiative’s effectiveness) and Self-Efficacy (perceptions of one’s ability to successfully execute actions that will lead to a desired outcome) were found to be positively associated with low–fat diet intentions, whereas severity and vulnerability were not ( Bandura, 1982 ; Plotnikoff and Higginbotham, 1995 ). One of the study’s aims was to use a multidimensional measure of healthy eating behavior that included both intake of fruits and vegetables as well as items with less harmful fat. More significantly, previous research on severity and susceptibility has indicated that both of these factors adversely influence healthy lifestyle goals, contrary to what PMT suggests ( Plotnikoff and Higginbotham, 2002 ).

Increased vulnerability was shown to be adversely connected to workout goals. Recently, several researchers conducted a study on teenage perceptions of the risk for cardiovascular disease. Interestingly, greater assessments of the severity of cardiovascular disease indicated the desire to consume fatty meals. Perceived danger can lead to maladaptive or defensive behaviors at low levels of effectiveness ( Umeh, 2003 ). As a result, some of the Umeh research participants may have had low esteem or behavioral efficacy, and hence behaved defensively to perceived threat. Unfortunately, neither Plotnikoff and Higginbotham’s nor Umeh’s studies directly tested this. Overall, it is yet unknown how threat perception will influence healthy eating habits. Even though many students are neither obese or overweight and so may get away with a bad diet, adopting good eating habits in college may inculcate habits that will help avoid a range of obesity concerns in the future. Obesity, as previously said, has become a more serious health issue than cigarette smoking or alcohol consumption. Additionally, one might minimize their alcohol intake by avoiding specific social occasions. Students, on the other hand, are faced with a range of dietary and nutritional choices on a regular basis ( Huang et al., 2003 ). These challenging choices, together with findings indicating over 20% of college students are overweight or obese, imply that severity and susceptibility are two powerful factors that may influence college students’ eating decisions.

However, little is known about the relationship between perceived obesity dangers and eating habits. Previous study findings give little reason to believe that a favorable association between threat perception characteristics and healthy eating behavior may be predicted. If a negative relationship between these factors is discovered, future researchers may look at ways to reduce weight-related anxiety. As a result, the study’s initial purpose was to look at the primary effects of perceived severity, perceived vulnerability, and fear on junk food consumption. In this regard the following hypotheses were formulated to analyze the relationship of these with the junk food eating behavior leading to obesity.

H 1 : Perceived severity has a negative effect on junk food eating behavior. H 2 : Perceived vulnerability has a negative effect on junk food eating behavior. H 3 : Fear has a negative effect on junk food eating behavior.

Relationship of Junk Food Eating Behavior With Obesity

A lot of research in this regard has been carried out previously in different perspectives. There is a general notion that eating unhealthy or junk food leads to obesity which is considered as a disease in some contexts ( Huang et al., 2003 ; Bayol et al., 2007 ; Yaniv et al., 2009 ; Datar and Nicosia, 2012 ; Hemmingsson, 2018 ; Robinson et al., 2021 ). The prevalence of bad eating habits has been connected to the adoption of a western lifestyle by individuals in emerging countries. A lack of consistency in eating breakfast, a low frequency of fruit and vegetable intake a proclivity toward increased junk food consumption, and a high prevalence of soft drink use are all examples of harmful dietary patterns. Breakfast consumption contributes to positive changes in the appetitive, hormonal, and neurological signals that regulate food intake, whereas missing breakfast leads to obesity. Fruits and vegetables, on the other hand, are high in water and fiber that have a low energy density ( Huang et al., 2003 ; Bayol et al., 2007 ; Sun, 2008 ; Yaniv et al., 2009 ; Datar and Nicosia, 2012 ; Loef and Walach, 2012 ; Mc Morrow et al., 2017 ; Hemmingsson, 2018 ; Robinson et al., 2021 ). As a result of the satiating impact of fiber, they defend against obesity by resulting in fewer calories ingested and the displacement of energy-dense meals. Junk food and soft drinks, on the other hand, are high in energy and contain empty calories, which contribute to obesity. Thus, the changing dietary patterns, which simultaneously include a higher consumption of the more energy-dense food and a lower consumption of the less energy-dense food, could be causing double harm ( Faizi et al., 2018 ). These supported literatures and the pre-existing relationship allowed us to find the impact of junk food eating behavior on obesity and we devised the following hypothesis.

H 4 : Junk food eating behavior has a positive effect on obesity.

Mediating Role of Junk Food Eating Behavior

There is a general notion that eating unhealthy or junk food leads to obesity which is considered a disease in some of the contexts ( Huang et al., 2003 ; Bayol et al., 2007 ; Yaniv et al., 2009 ; Datar and Nicosia, 2012 ; Hemmingsson, 2018 ; Robinson et al., 2021 ). The prevalence of bad eating habits has been connected to the adoption of a western lifestyle by individuals in emerging countries. A lack of consistency in eating breakfast, a low frequency of fruit and vegetable intake, a proclivity toward increased junk food consumption, and a high prevalence of soft drink use are all examples of harmful dietary patterns. Breakfast consumption contributes to positive changes in the appetitive, hormonal, and neurological signals that regulate food intake, whereas missing breakfast leads to obesity. Fruits and vegetables, on the other hand, are high in water and fiber and have a low energy density ( Huang et al., 2003 ; Bayol et al., 2007 ; Sun, 2008 ; Yaniv et al., 2009 ; Datar and Nicosia, 2012 ; Loef and Walach, 2012 ; Mc Morrow et al., 2017 ; Hemmingsson, 2018 ; Robinson et al., 2021 ).

Although, it is evident from the literature that certain behaviors could mediate the relationships between vulnerability, obesity, severity and fear but no prior research has focused on evaluating the mediating role of junk food eating behavior. This leads to utilizing this behavior as mediator in our context of the study. It was suggested by looking into the habitual behaviors playing a mediating role between change in symptoms of depression and food related behaviors ( Owens et al., 2021 ). Certain attitudes have been reported in past to be mediated by some behaviors for eating healthy. For an instance, diet relationships at educational level in directing attitudes toward healthy eating have been studied in past and offered some significant results ( Lê et al., 2013 ). It was further suggested by Wu et al. (2019) , that dietary behaviors whether eating junk or healthy food could mediate the relationships between obesity and food insecurity. This research provided an insight about mediating role of behavior of junk food eating. Keeping in view the novelty of this behavior as a mediator between perceived severity and obesity, perceived vulnerability and obesity and fear and obesity, we hypothesized the following for analysis.

H 5 : Junk food eating behavior mediates the relationship of perceived severity and obesity. H 6 : Junk food eating behavior mediates the relationship of perceived vulnerability and obesity. H 7 : Junk food eating behavior mediates the relationship of fear and obesity.

Moderating Role of Product Knowledge Hiding

Researchers discovered that, while rationalizing their actions, knowledge hiders foresaw impaired relationships ( Connelly and Zweig, 2014 ). There are other grounds to suspect that managers from different companies might purposefully conceal information during commercial interactions, isolating companies. For example, a providing manager may be hesitant to share information with the purchasing manager because he does not completely trust the latter ( Hernaus et al., 2018 ). Lack of interpersonal interactions is one aspect that might contribute to a lack of trust. Managers from different organizations may also suppress knowledge during their supply chain interactions if they feel that sharing, would have a negative impact on them or they will get no personal advantage, if they share it with their supply chain counterpart. Managers can also hide knowledge if their organization’s culture encourages it.

Employees may act in ways that are counter to their role expectations but yet adhering to company rules in order to maintain their employment. Another explanation might be possible, if managers from different companies dislike one other during business interactions, resulting in them withholding information from one another. According to the researchers, managers’ capacity to explore and develop new ideas, execute change, apply new information, or improve procedures to increase personal and corporate performance and understanding is harmed by knowledge concealing ( Arain et al., 2020 ). The literature on the buyer–supplier interaction in the supply chain is few and elusive. In other words, it does not explain why purchasing and supplying business executives keep information from one other throughout supply chain interactions ( Avotra et al., 2021 ; Yingfei et al., 2021 ; Dar et al., 2022 ). Moderating role of knowledge hiding and hiders is studied less in past, e.g., ( Chatterjee et al., 2021 ) but it provided us to analyze and find deep into the said moderation between junk food eating behaviors and the outcome of it, “obesity.” So we hypothesized the following.

H 8 : Product knowledge hiding moderates the effect of junk food eating behavior on obesity.

This research is based on the following conceptual model (see Figure 1 ) for the analysis of perceived health threats on developing junk food eating behavior leading to obesity with a moderating effects of product knowledge hiding.

Conceptual model.

Methodology

This study is based on the quantitative analysis where the effects of perceived severity, perceived vulnerability and fear are checked on the obesity of kids through junk food eating behavior. The moderating role of product knowledge hiding had been measured on the relationship of junk food eating behavior and obesity of teenagers. The population of the study were the kids and adolescents in their teens who are more involved in junk food eating behaviors ( Boylan et al., 2017 ). The total number of kids and adolescents reached out for the data collection were 400 however the usable responses received were 228. The sampling method used in this study is purposive sampling as getting track of all kids and adolescents in China is not easy ( Saha et al., 2021 ). Therefore, the kids and adolescents were reached on purpose for data collection. This was an adequate group for obesity to be checked as they are among the group who are highly involved in junk food eating. The data collection method used through survey questions, and the participants were informed in advance for their services to be rendered for the data collection purpose. The guardians of the respondents were also informed to give consent if they want to participate or not and, the anonymity of the respondents was ensured. The questionnaires were distributed individually and were given time to fill it out and it was Self-Administered to avoid any ambiguities. Questionnaires were the best technique to be used for data collection as it documents the responses and gives respondents option to the severity of the agreement of the respondents. The data was statistically treated with the help of Smart-PLS software for the structural equation modeling because it measures the relationships simultaneously for all the variables.

Instrument Development

The instrument used for data collection is the questionnaire-based survey. There were 31 items in total in the survey which were adapted from the previous studies as there were found most appropriate in the literature that represent the variables of the present study. The 6-items scale for the junk food eating behavior has been adapted from ( Schlundt et al., 2003 ). It addressed the eating behavior patterns and the involvement of the respondents in junk food. This questionnaire was especially designed in understanding the junk food eating behaviors. The measurement scale for perceived severity and perceived vulnerability were consisted of 4-itesms each, while the measurement scale for the variable fear contained three items. These three scales have been adopted from ( Pang et al., 2021 ) who had measured the role of these three variables in the organic food patterns of the respondents. Further, the variable of obesity is measured with a 10-item scale developed by Schlundt et al. (2003) . Additionally, the variable of product knowledge hiding had been adapted and modified according to the study taking the playing dumb perspective of the knowledge hiding developed by Connelly et al. (2012) . It fits the product knowledge hiding variable of the present study in the best appropriate way. It consisted of 4-items (sample items: “Pretended that I do not know which information is related to product,” and “explains that, I have no knowledge about the constituents of this product,” etc.). The previously established scales were found most appropriated addressing the constructs of variables used in the present study. Furthermore, the scales used in this study were validated with discriminant validity and convergent validities along with the Cronbach α and composite reliabilities. The average variance extracted had also been used to verify the validity of the scales used. The details for reliabilities and validities are given in the following sections.

Demographics Details

The first section of the questionnaire was consisted of the demographic information for the respondents. The population of the study were the kids and the teenagers therefore, the age was divided into two main categories only, i.e., below 12 and above 12. The education was divided into three categories of grades 5–10, 11–12, and above 12 because the respondents of the study fall in kids and teen categories. The details of the demographic analysis are given in table analysis are given in Table 1 .

Demographics analysis.

N  = 228.

Data Analysis and Results

Data of the study were analyzed with the software Smart-PLS for the partial least square structural equation modeling. In this software, the relationships of the independent variables (i.e., perceived severity, perceived vulnerability and fear) are measured with the junk food eating behavior and its consequence in the form of obesity. The moderating effect of product knowledge hiding has been checked for the effect of junk food eating behavior on obesity of the kids and adolescents. Smart-PLS measures the model in two phases, i.e., measurement mode and the structural mode. The measurement model gives the validity and reliability of the scales, while structural model checks the acceptance or rejection of the hypothesis based on the statistics produced like r -square, f -square, t -statistics, p -values, and the β values.

Measurement Model

The measurement model reports the validities, reliabilities, and β values of the variables. The output for the measurement model has been represented in the Figure 2 .

Output of measurement model. PS, perceived severity; PV, perceived vulnerability; JF, junk food eating behavior.

The statistics for the factor loadings, reliabilities and average variance extracted are reported in the Table 2 . The minimum threshold for the reliabilities and the factor loadings of the items has been reported as 0.7 ( Henseler et al., 2015 ). All the values obtained in this study are above this threshold, thus meeting the criteria of convergent validities of the scale. The minimum values obtained for factor loadings are 0.701, rest of the values are above this thus making the scale convergent valid. The values for outer variance inflation factor of the items used in this study to check the collinearity among the items, however, all are found significant as they all are less than the threshold mentioned in the literature ( Grewal et al., 2004 ). Similarly, the reliabilities obtained in this study for the variable, minimum statistics for Cronbach alpha reliability is 0.752 and for composite reliability is 0.846, which are well above the prescribed threshold in the literature. Further, the average variance extracted is reported to be above 0.5 ( Di Marco et al., 2018 ). The minimum value obtained in this study for AVE is 0.565.

Factor loadings, reliabilities, VIF, and AVE.

Another measure used for validity checking is the heterotrait-monotrait (HTMT) ratio and the Fornell and Larcker Criteria. These are the validity measures for discriminant validities of the scales. Present study has also employed these two validity tests to measure the discriminant validity of the scaled adapted in this study. The results of the HTMT ration are supposed to show values less than 0.9 ( Franke and Sarstedt, 2019 ), which are reported in Table 3 . The reported values for HTMT ration are below the mentioned cut off criteria. The maximum value obtained for HTMT ratio for this study is 0.808.

HTMT ratio.

JF, junk food eating behavior; PS, perceived severity; PV, perceived vulnerability; PKH, product knowledge hiding.

Similarly, another statistical test used is Fornell and Larcker Criteria. The values obtained should show the highest value at the top of the column for each variable ( Franke and Sarstedt, 2019 ). The present study meets this criteria, as the highest values lie at the top for each variable. The results can be seen in Table 4 .

Fronell and Larcker Criteria.

Moreover, the adjusted r -square reported for the study are 52.9% for junk food eating behavior and 40.4% for the obesity variable, that shows the variables used in this study for the prediction of junk food eating and obesity are relevant to these variables. Similarly the inner VIF values have also been found within the significant range, i.e., 3.3 ( Grewal et al., 2004 ).

Structural Model

The output for the structural model is shown in Figure 3 . It shows the strength of the relationship of the independent variables with the dependent variables along with significance.

Output of measurement model with moderation. SD, standard deviation; JF, junk food eating behavior; PS, perceived severity; PV, perceived vulnerability; PKH, product knowledge hiding.

The Table 5 of the study reports the mean sample and original sample with the t -stats and p -values obtained for each hypothesis of the study. The results obtained go along the hypotheses generated in this study. Perceived severity, perceived vulnerability and fear show the negative relationships with the junk food eating behavior which is justified with the results obtained. Similarly, the junk food eating behavior shows a positive and significant relationship with obesity among the kids.

Direct effects.

H, hypothesis; O, original sample; M, sample mean; SD, standard deviation; JF, junk food eating behavior; PS, perceived severity; PV, perceived vulnerability; PKH, product knowledge hiding.

The first hypothesis of the study could not find significant outcome owing the effect of perceived severity on junk food eating ( H 1 : t -stats = 0.261, p  > 0.05), hence the first hypothesis of the study is rejected. The second hypothesis ( H 2 : Perceived vulnerability has a negative effect on junk food eating behavior; t -stats = 11.032, p  < 0.001, β  = −0.597) is accepted with a negative effect on junk food eating behavior. Regarding third hypothesis of the study ( H 3 : Fear has a negative effect on junk food eating behavior, t -stats = 3.987, p  < 0.000, β  = −0.216) has shown significant negative effects on the junk food eating behaviors. Similarly, the fourth hypothesis ( H 4 : Junk food eating behavior has a positive effect on obesity, t -stats = 15.682, p  < 0.001, β  = 0.316) is accepted with junk food eating behavior showing a positive significant effect on the obesity of the kids and adolescents ( Table 6 ).

Indirect effects.

Regarding the indirect effects of the study, two relationships have been found significant while one could not find any significance in this study. The mediation of junk food between fear and obesity have been found to have negative significant effect, t -stats 3.583, p  < 0.05, β  = −0.137. Similarly perceived vulnerability also found to have significant negative relationship with obesity in the presence of junk food t -stats 9.20, p  < 0.001, β  = −0.378 ( Figure 4 ).

Output of structural model with moderation. PS, perceived severity; PV, perceived vulnerability; JF, junk food eating behavior; PKH, product knowledge hiding.

Product knowledge hiding has been used as the moderating variable in this study that is proposed to moderate the relationship between junk food eating behavior and obesity. Before measuring the significance of the hypothesis of moderations, the measurement model was again checked for reliability and validity of the scale. These all have been found significant; the reliabilities had been reported as 0.895 for junk food eating behavior, 0.752 for the variable fear, 0.919 for obesity, perceived vulnerability 0.826 and 0.755 for perceived severity. Similarly, the validities had also been under the prescribed values mentioned ( Table 7 ).

Moderating effects.

H, hypothesis; O, original sample; M, sample mean; SD, standard deviation; PKH, product knowledge hiding.

Moving to the fifth hypothesis ( H 5 : Product knowledge hiding moderates the effect of junk food eating behavior on obesity, t -stats 4.487, p  < 0.001, β  = −0.213) showing higher awareness of the product knowledge hiding, weaker will be the relationship of junk food eating behavior and obesity among kids.

There was a strong need of conducting the research on perceived health related threats for developing junk food eating behaviors which ultimately leads to obesity. Our research focused on the developed model discussed earlier in which constituents of the perceived threats were analyzed for their impact on developing junk food eating behaviors. Such behaviors were setting on the renowned obesity considered as disease in previous literature. Perceived severity, perceived vulnerability and fear were the elements drawn from the perceived health threats suggested by HBM by Gochman and Saucier (1982) and supported by protection motivation theory by Rogers (1975) . The analysis was conducted through Smart-PLS which yielded into mixed results regarding associations of these factors which ultimately leads to obesity.

Our first hypothesis which was about perceived severity having a negative effect on junk food eating behavior. This hypothesis was rejected, and the reason of its rejection was the strong and positive association of perceived severity with eating junk food behaviors. These results are in accordance to some researchers such as ( Tavassoli et al., 2018 ). It is obvious that, prior to taking any action to conduct a certain behavior, persons’ knowledge and awareness of the issue should be evaluated, and they should be educated, if their understanding of the behavior and its many elements is lacking. They should then be taught how to do that activity. In that instance, it is expected of the individual to excel at a certain behavior. According to these findings, perceived severity necessitates greater attention since low perceived severity might lower accuracy in completing the action, leading to people eating more junk food.

The second hypothesis which was about impact of perceived vulnerability on developing junk food eating behaviors was accepted as perceived vulnerability under the umbrella of perceived health threat put a negative impact on eating junk food and developing this behavior. These results are supported by the previous studies of various researchers in different perspectives such as ( Umeh, 2003 , 2004 ). Our next hypothesis was about perceived fear of eating junk food behavior. This proposition was also accepted as fear had negative association with developing junk food eating behavior. The fear of getting obese led to the production of such results in which it is considered as a disease. This fact is also supported by the development of not eating junk food behaviors in the fitness freaks. Similar findings were obtained by previous researchers in different contexts such as during pandemic ( Robinson et al., 2021 ).

The fourth hypothesis was about eating junk food behaviors which lead to obesity was supported by many researchers of the past with the reasoning of development of such behavior would resultantly set on the obesity ( Huang et al., 2003 ). This is established from decades that behavior of eating unhealthy or the junk food leads to the obesity. so, our hypothesis results were in accordance to such previous researches. The fifth, sixth and seventh hypothesis responded to the mediating role of junk food eating behavior as a mediator between perceived health threats such as perceived severity, perceived vulnerability, fear and obesity. The results indicated that these relationships could be aided by junk food eating behaviors. Although, it is evident from the literature that certain behaviors could mediate the relationships between vulnerability, obesity, severity and fear but no prior research has focused on evaluating the mediating role of junk food eating behavior. This leads to utilizing this behavior as mediator in our context of the study. It was suggested by looking into the habitual behaviors playing a mediating role between change in symptoms of depression and food related behaviors ( Owens et al., 2021 ).

Certain attitudes have been reported in past to be mediated by some behaviors for eating healthy. For an instance, diet relationships at educational level in directing attitudes toward healthy eating have been studied in past and offered some significant results ( Lê et al., 2013 ). It was further suggested by Wu et al. (2019) , that dietary behaviors whether eating junk or healthy food could mediate the relationships between obesity and food insecurity. This research provided an insight about mediating role of behavior of junk food eating. Therefore, mediated the direct effects of perceived health threats on obesity. Our last hypothesis was also accepted and yielded significant results and hiding information regarding the products significantly moderates or regulates the association between eating junk food behaviors and the setting of obesity resultantly. These associations are strongly influenced by the product knowledge hiding. As knowledge hiding regarding products would put the consumers on unconsciousness that what they are eating and what would it impact on their health. Such moderating roles of knowledge hiding have been partially studied before such as moderating role of knowledge hiders in different perspective was studied by Hemmingsson (2018) . This study provides a handful insight on developing healthy eating behaviors so, it could lead to healthy lives.

Theoretical Contribution

The present study makes following theoretical contributions to the literature. (1) To the best of our knowledge, this is among the initial studies that check the role of perceived severity, perceived vulnerability, and fear in affecting the junk food eating behaviors. It has shown that the awareness can create the cautious behavior among the users regarding junk foods. (2) The study has estimated that the awareness of the perceived threats creates the negative relationship with the junk food eating that detains the kids and adolescents from eating junk foods. (3) This is already a proven fact that the use of junk food causes obesity among the users. However, the awareness of the product knowledge hiding from the manufacturers end has a negative impact on the positive relationship of junk food eating behavior and obesity. When there is less awareness of product knowledge hiding, more obesity will be seen due to junk food.

Managerial Implications

There are certain managerial implications of the present study. (1) General public should be made aware of the product contents and the warnings for any undesirable results of using the junk food eating. (2) There lies the responsibility of the manufacturing firms that they should not hide any knowledge about the contents and products moved to the market so the consumers should be aware of the dangers associated and the products used. (3) Obesity being one of the major health issues globally, it is important to make kids aware how to read the information written on the product packages and how it can be helpful for them to understand the risks associated with it.

Future Research Direction and Limitation

This study has few limitations as well. First of all, it is a cross sectional study, a panel data analysis is required to study if the awareness about the junk food eating behaviors is made available, does this lessens the cases of obesity. Second, it is conducted in China, where less obesity is seen due to healthy eating behaviors, it should be conducted in United States or other Western countries where obesity is a genuine issue. Third, the study has not considered the warning labels on the products information, role of these warning labels can be seen in future, how it affects the junk food eating behaviors among kids. Another limitation of the study is that it has used purposive sampling with kids and adolescents as population. Future study should be conducted taking different age groups including adults as well to know the trend of junk food eating behaviors among them.

Obesity has become a global issue since the junk foods have been brought to the market. These foods are presented in such an attractive way that kids cannot resist it. However, the manufacturing companies have been hiding certain contents of the products that are major factors for the obesity in the junk food users. Therefore, this study has attempted in measuring the role of junk food eating behavior in obesity among kids and adolescents. However, the role of perceived threats in the form of perceived severity for the use of product, perceived vulnerability of the products and fear of using the product containing obesity triggering contents have been found to have negative impact on the junk food eating behavior. This shows if adequate awareness is given and the perceived threats are mentioned to the kids than it will not engage in the junk food eating behaviors. Furthermore, the awareness of product knowledge hiding has been found to have significant moderation on the relationship of junk food eating behavior and obesity.

Data Availability Statement

Ethics statement.

The studies involving human participants were reviewed and approved by Xian University of Architecture & Technology (XUAT), China. The patients/participants provided their written informed consent to participate in this study. The study was conducted in accordance with the Declaration of Helsinki.

Author Contributions

YL and XL: writing the draft and conceptualization. TZ, HG, and CS: data collection and funds acquisition. All authors contributed to the article and approved the submitted version.

This study was supported by the General project of the National Social Science Fund (20BTY072) and the Education Department of the Shaanxi Provincial Government (18JK0423).

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s Note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

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