Eating more ultra-processed food links depression and diabetes

By Dr. Liji Thomas, MDReviewed by Lauren HardakerJul 30 2025

New research reveals that eating more junk food doesn’t just harm your waistline; it could also increase the risk of diabetes for people with depression, highlighting the urgent need for healthier food choices and public policy action.

Study: Ultra-Processed Food Intake as an Effect Modifier in the Association Between Depression and Diabetes in Brazil: A Cross-Sectional Study. Image credit: Rimma Bondarenko/Shutterstock.com

A recent study published in Nutrients investigated how eating junk food (ultra-processed food or UPF) increases the risk of associated diabetes and depression in an adult Brazilian cohort.

Introduction

Depression is a mental health disorder characterized by the loss of enjoyment of life and experiencing a persistently low mood. The recent coronavirus disease 2019 (COVID-19) pandemic was linked to about 53 million cases of depression. This led to a significant increase in the number of depression cases worldwide to 246 million.

People in or past middle age are at higher risk for major depression and related disability, as it affects their mental and social health and well-being adversely, impacting their daily functioning and quality of life.

Depression is linked to emotional eating, where people eat to make themselves feel better, often choosing UPF. Increased UPF intake predicts higher odds of metabolic disorders, including cardiovascular disease, diabetes, or obesity.

A commonly used classification system called NOVA describes UPFs as industrially manufactured edibles containing multiple ingredients not found in typical home-cooked food and considered unhealthy additives. These include dyes, flavoring substances, and emulsifiers. They are rich in calories from saturated fats, refined flours, and sugars, but have a reduced nutrient content.

Despite extremely high rates of diabetes and obesity in developing countries, most such research is from developed countries, especially the United States, Italy, and South Korea.  Americans derive half their energy intake from UPF.

Several factors increase the risk of UPF in younger people, including increased exposure to food marketing and a declining interest in healthy dietary habits. UPFs are also widely and conveniently available.

People with both depression and diabetes are especially at risk for poor health. Functional disability is three-fold more likely than those with diabetes only, and over two-fold compared to those with only depression. With no common genetic factors, the role of environmental factors in such associations is very significant. These include education, lifestyle, and socioeconomic status.

Brazil is a large developing country with rising rates of both depression and diabetes. Ten percent of the population suffers from major depression, making it a leading cause of disability in Brazil and putting the country among the top three for depression prevalence among developing countries. UPF consumption made up 9% of total energy intake in Brazil in the 1990s, vs >20% at present. These facts motivated the current study in Brazil.

About the study

Data came from the 2019 Brazilian National Health Survey, with over 87,000 participants between 18 and 92 years, of whom 81,524 were included in the primary analysis after exclusions. Their self-reported incidence and prevalence of diabetes and depression, their dietary habits, along with demographic and socioeconomic characteristics, were analyzed using multivariate logistic regression models.

UPF consumption was stratified as high and low weekly intake. The food group intake was measured as vegetables, legumes, and fruits or natural fruit juice; artificial juices, sodas, sweets; meal substitutes including bars and shakes; red or white meat, fish, or milk.

Activity, unhealthy habits including smoking and drinking, and obesity, were also accounted for. High UPF consumption was classified as: UPF-1, where one UPF was consumed above the population median and UPF-2, where all UPF consumption rates were higher than the median

Study results

About 70% of the group were high-UPF-1 vs 4% with the UPF-2 criteria. A third were physically active, but nearly 80% were low-income and living in an urban setting. The mean age was 47 years.

UPF intake

Among the high-UPF participants in either group, depression was associated with a ~25% higher odds of diabetes, compared to low-UPF consumption. This was true even after adjusting for meat and vegetable intake and demographic differences.

UPF intake modifies some of the diabetes risk in depression, especially under high-UPF-2 conditions. Overall, diabetes was associated with depression only in those with high UPF intake. With UPF-2, both low and high intake strengthened the association of diabetes with depression, but more so with high consumption.

Conversely, high UPF-1 intake predicted a significantly lower risk of diabetes in some models. However, the researchers note this likely reflects “reverse causality”, that is, individuals diagnosed with diabetes may have reduced their UPF consumption as part of dietary management, rather than UPF intake being protective. With high UPF-2, there was no significant association.

The effect of age

When stratified by age, the trends were magnified. Depression with diabetes was more prevalent among older adults, irrespective of UPF intake. People with either diabetes or depression were at higher risk of having other conditions as well, at 23% and 13% prevalence, respectively.

In contrast, the association between depression and diabetes was especially strong among younger people in the high UPF-2 group, suggesting that high UPF intake amplified this risk in younger adults. The model indicates that UPF consumption explained more of the association of diabetes with depression when older adults are excluded. Emotional eating and stress, seen in depression, may explain the presence of diabetes. The reverse is also true.

Younger people with depression were more likely to have diabetes with high vs low UPF intake. The association is stronger with a high UPF-2 intake. This underlines the need for psychological support in younger people diagnosed with diabetes, who tend to turn their feelings of shame and blame inward, towards themselves. Besides emotional eating, depression may be promoted by gut dysbiosis induced in part by UPF intake.

It is important to remember that this study's results cannot determine whether UPF intake causes diabetes or depression; only that these are linked in the population studies can be determined.

Conclusions

“These findings suggest that high UPF intake may influence the relationship between depression and diabetes, especially in younger adults.” Further studies will help establish the mechanisms and the potential of dietary interventions in at-risk individuals as well as causality.

For instance, practitioners could routinely screen the eating habits of younger adults with either depression or diabetes, coupled with personalized counseling directed at reducing UPF intake. Policies should include clear and prominent labeling of UPF, educational and awareness campaigns, marketing restrictions to protect at-risk populations, and the formulation of guidelines that integrate metabolic and mental health.

The authors emphasize that depression can increase diabetes risk (potentially via emotional eating, stress, or medication) and diabetes can increase depression risk (via psychological or biological pathways). UPF intake may exacerbate both directions of this relationship, especially in younger people.

As with any study using self-reported diagnoses and dietary habits, the authors caution that recall bias and measurement limitations may affect the results. Not all ultra-processed foods or confounders could be accounted for.

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