Does Eating Lots of Junk Food Lead to Poor Mental Health?

• A meta-analysis published in BMC Psychiatry examined the results of 17 studies and found that high junk food consumption is associated with poorer mental health.
• Junk food consumption was associated with 15% higher odds of having depression and experiencing stress.
• Odds of developing mental health disorders were 16% higher in individuals consuming lots of junk food.

Not all foods and beverages are equally healthy. Some foods are rich in essential nutrients, minerals, fibers, and other ingredients our body needs to function well. These foods generally support our long-term health. Other types of food tend to be rich in ingredients used solely to increase their palatability and to make them more appealing to people. These unhealthy foods often have large quantities of refined sugars added, causing blood sugar spikes and crashes after consumption. They also tend to contain various artificial additives to increase their taste and improve chemical or mechanical properties. These ingredients typically have no nutritional value and are linked to increased risks of health problems (e.g., Huang et al., 2023; Lane et al., 2024).

Junk food

One important category of foods typically considered unhealthy is junk food. Junk food is the name coined in the 1970s to refer to foods that are energy-dense (i.e., high in calories), but have low nutritional value. These foods contain refined sugar, white flour, trans fat, polyunsaturated fat, salt, and numerous food additives. They tend to lack protein, minerals, and fiber (Rajveer & Monika, 2012). A rule of thumb is that if a food item has a long list of ingredients with many names of chemical compounds or artificial ingredients, it is likely junk food.

Junk food is easy to produce (industrially), tastes good, and typically has a long shelf life without requiring refrigeration. Most often, junk food is ultra-processed, meaning it is made mostly or entirely from substances derived from foods and additives with few or no unprocessed components (Monteiro et al., 2018).

Junk food and health

Junk food is made highly palatable by combining high concentrations of easily digestible fats and sugar. When fats and sugars enter the human digestive system, they trigger separate neural pathways linking to reward areas of the brain. When they are digested simultaneously, both pathways are triggered, producing a very strong rewarding experience (Hedrih, 2024; McDougle et al., 2024). This is the likely mechanism behind the extreme pleasure we feel when we eat chocolate, for example.

When fats and sugars enter the human digestive system, they trigger separate neural pathways linking to reward areas of the brain.

Studies have shown that these experiences also promote overeating and may, in time, dysregulate the brain’s food intake mechanism to control how much food a person eats (Hedrih, 2024). This leads to obesity. In studies on rodents, when researchers want to make animals obese, they feed them food rich in easily digestible fats and sugar (Ikemoto et al., 1996). This is called an obesogenic diet.

Junk food, particularly ultra-processed foods, also tends to contain additives, many of which are added to make the food even more palatable and produce effects similar to those found in addictions (Gearhardt et al., 2023; Hedrih, 2023a). Many studies have linked regular consumption of junk food or its main components, such as refined sugar, with increased risk of various adverse health conditions (Hedrih, 2023b; Huang et al., 2023; Zhang et al., 2024).

Junk food contains additives, many of which are added to make the food even more palatable and produce effects similar to those found in addictions 

The current study

Study author Hanieh-Sadat Ejtahed and her colleagues conducted a meta-analytic study to integrate existing scientific findings about the links between junk food consumption and mental health disorders in adults (Ejtahed et al., 2024). They searched multiple databases of scientific publications for studies reporting on this link. The search yielded 17 such studies conducted on data from 159,885 participants.

As studies about junk food often do not use the term junk food, these authors considered a study to be about junk food if it was about one of the following types of foods, beverages, or food/beverage components (see Figure 1):

• Sweet drinks: fruit-flavored drinks, sweetened coffee, fruit juice drinks, sugared coffee and tea, energy drinks, cola drinks, beverages, soft drinks, lemonade, and soda.
• 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),
• 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;
• Total junk foods: Different types of junk food are considered together. These were either studies on junk food or studies focusing on multiple categories of junk food.

 

Figure 1. Junk foods included in Ejtahed et al. (2024)

 

Junk food consumption is associated with higher mental health symptoms

The results showed that all studies reported at least some associations between mental health symptoms and junk food consumption. However, it sometimes happened that one study found a specific mental health issue to be associated with junk food consumption, but another did not.

Overall, studies indicated that individuals consuming junk food tend to have 15% higher odds of having heightened stress and depression symptoms. Two studies focused on stress showed that individuals consuming junk food had a 31% higher risk of experiencing heightened stress symptoms compared to those not consuming junk food or eating it less.

Results of longitudinal studies, studies that followed groups of participants over time, indicated that individuals consuming junk food regularly have 16% higher odds of developing mental health disorders compared to those who do not eat junk food or eat it less. Frequent consumers of junk food developed depression 30% more often than individuals consuming it less often or not at all (see Figure 2).

 

Figure 2. Junk food is associated with Depression symptoms

Conclusion

Overall, the study showed that individuals consuming high amounts of junk food regularly tend to have poorer mental health compared to those consuming it less often or not at all. In particular, they were somewhat more likely to develop mental health disorders, have heightened depressive symptoms, and experience stress.

The study showed that individuals consuming high amounts of junk food regularly tend to have poorer mental health compared to those consuming it less often or not at all.

The cause of this association remains insufficiently clear. Studies have identified some possible mechanisms through which junk food could affect mental health. These include neuroinflammation and changes in the body’s functioning that result from obesity. However, it also remains possible that mental health problems make it harder for individuals to maintain a healthy diet, leaving them with the easier and, most often, more accessible option, which is junk food.

Note: Mechanisms through which consumption of junk food influences depression and mental health symptoms can be found in NP 150 Parts I and II.

The paper “Association between junk food consumption and mental health problems in adults: a systematic review and meta-analysis” was authored by Hanieh-Sadat Ejtahed, Parham Mardi, Bahram Hejrani, Fatemeh Sadat Mahdavi, Behnaz Ghoreshi, Kimia Gohari, Motahar Heidari-Beni, and Mostafa Qorbani.

References

Ejtahed, H.-S., Mardi, P., Hejrani, B., Mahdavi, F. S., Ghoreshi, B., Gohari, K., Heidari-Beni, M., & Qorbani, M. (2024). Association between junk food consumption and mental health problems in adults: A systematic review and meta-analysis. BMC Psychiatry, 24(1), 438. https://doi.org/10.1186/s12888-024-05889-8

Gearhardt, A. N., Bueno, N. B., DiFeliceantonio, A. G., Roberto, C. A., Jiménez-Murcia, S., & Fernandez-Aranda, F. (2023). Social, clinical, and policy implications of ultra-processed food addiction. BMJ, e075354. https://doi.org/10.1136/bmj-2023-075354

Hedrih, V. (2023a). Scientists Propose that Ultra-Processed Foods be Classified as Addictive Substances. CNP Articles in Nutritional Psychology. https://www.nutritional-psychology.org/scientists-propose-that-ultra-processed-foods-be-classified-as-addictive-substances/

Hedrih, V. (2023b, June 6). Health Consequences of High Sugar Consumption. CNP Articles in Nutritional Psychology. https://www.nutritional-psychology.org/health-consequences-of-high-sugar-consumption/

Hedrih, V. (2024, February 19). Consuming Fat and Sugar (At The Same Time) Promotes Overeating, Study Finds. CNP Articles in Nutritional Psychology. https://www.nutritional-psychology.org/16563-2/

Huang, Y., Chen, Z., Chen, B., Li, J., Yuan, X., Li, J., Wang, W., Dai, T., Chen, H., Wang, Y., Wang, R., Wang, P., Guo, J., Dong, Q., Liu, C., Wei, Q., Cao, D., & Liu, L. (2023). Dietary sugar consumption and health: Umbrella review. BMJ (Clinical Research Ed.), 381, e071609. https://doi.org/10.1136/bmj-2022-071609

Lane, M. M., Gamage, E., Du, S., Ashtree, D. N., McGuinness, A. J., Gauci, S., Baker, P., Lawrence, M., Rebholz, C. M., Srour, B., Touvier, M., Jacka, F. N., O’Neil, A., Segasby, T., & Marx, W. (2024). Ultra-processed food exposure and adverse health outcomes: Umbrella review of epidemiological meta-analyses. BMJ, e077310. https://doi.org/10.1136/bmj-2023-077310

Ikemoto, S., Takahashi, M., Tsunoda, N., Maruyama, K., Itakura, H., & Ezaki, O. (1996). High-fat diet-induced hyperglycemia and obesity in mice: Differential effects of dietary oils. Metabolism, 45(12), 1539–1546. https://doi.org/10.1016/S0026-0495(96)90185-7

McDougle, M., de Araujo, A., Singh, A., Yang, M., Braga, I., Paille, V., Mendez-Hernandez, R., Vergara, M., Woodie, L. N., Gour, A., Sharma, A., Urs, N., Warren, B., & de Lartigue, G. (2024). Separate gut-brain circuits for fat and sugar reinforcement combine to promote overeating. Cell Metabolism. https://doi.org/10.1016/j.cmet.2023.12.014

Monteiro, C. A., Cannon, G., Moubarac, J.-C., Levy, R. B., Louzada, M. L. C., & Jaime, P. C. (2018). The UN Decade of Nutrition, the NOVA food classification and the trouble with ultra-processing. Public Health Nutrition, 21(1), 5–17. https://doi.org/10.1017/S1368980017000234

Rajveer, B., & Monika, O. (2012). Junk Food: Impact on health. Journal of Drug Delivery & Therapeutics, 2(3), 67–73.

Zhang, L., Sun, H., Liu, Z., Yang, J., & Liu, Y. (2024). Association between dietary sugar intake and depression in US adults: A cross-sectional study using data from the National Health and Nutrition Examination Survey 2011–2018. BMC Psychiatry, 24(110), 1–10. https://doi.org/10.1186/s12888-024-05531-7