Study Links Low-Calorie Diets with Increased Depression Symptoms

Link Between Diet and Depression

Recent research has established a connection between low-calorie diets and a slight increase in depressive symptoms, particularly among specific demographics such as overweight individuals and men. The study, a large observational analysis, assessed dietary habits and depression scores among over 28,000 adults in the United States.

Participants who followed calorie-restrictive or nutrient-restrictive diets exhibited higher emotional and physical distress compared to those who did not engage in dieting practices. This raises concerns regarding the potential negative impact of unsupervised restrictive diets on mental health in real-world settings.

Key Findings

The study, published in the open-access journal BMJ Nutrition Prevention & Health, suggests that men and overweight individuals are particularly susceptible to the adverse effects of restrictive eating. According to the research, a diet characterized by minimally processed foods, including fresh fruits and vegetables, whole grains, nuts, seeds, lean proteins, and fish, is generally associated with a lower risk of depression. Conversely, a diet heavily reliant on ultra-processed foods and high in refined carbohydrates and saturated fats tends to correlate with increased depression risk.

To delve deeper, researchers utilized data from the U.S. National Health and Nutrition Examination Survey (NHANES) from the years 2007 to 2018. A total of 28,525 adult respondents, comprising 14,329 women and 14,196 men, participated in the study and completed the Patient Health Questionnaire-9 (PHQ-9) to evaluate depressive symptom severity.

Out of the participants surveyed, 2,508 (approximately 8%) reported experiencing depressive symptoms. The breakdown included 7,995 individuals (29%) classified as having a healthy weight, while 9,470 (33%) were categorized as overweight, and 11,060 (38%) were deemed obese. Respondents indicated whether they were adhering to any specific diet for weight loss or other health reasons from a list of nine dietary options.

Dietary Patterns and Mental Health

Participants' dietary patterns were clustered into four categories:

• Calorie-restrictive diets
• Nutrient-restrictive diets (low in fat, cholesterol, sugar, salt, fiber, or carbohydrates)
• Established dietary patterns (e.g., tailored for diabetes)
• Individuals not on any specific diet

A substantial majority of participants (25,009, 87%) reported not being on a specific diet. In contrast, 2,026 (8%) were on calorie-restrictive diets, 859 (3%) adhered to nutrient-restrictive diets, and 631 (2%) followed established dietary patterns. Notably, a greater percentage of men (90%) reported not dieting compared to women (85%). Calorie restriction was most frequently noted among obese (12%) and overweight (8%) participants, while established dietary patterns were predominantly reported among those with obesity.

The findings revealed that those following calorie-restrictive diets had PHQ-9 scores that were, on average, 0.29 points higher than those not on any specific diet. Among overweight individuals adhering to calorie-restrictive diets, the increase was significant at 0.46 points, while nutrient-restrictive diets were associated with a 0.61 point increase in PHQ-9 scores. Additionally, these dietary practices were linked to heightened cognitive-affective symptoms and somatic symptom scores, especially among men.

Implications and Future Research

This research challenges previous findings suggesting that low-calorie diets may alleviate depressive symptoms. The discrepancies may stem from prior studies largely being randomized controlled trials, which ensured carefully monitored diets and balanced nutrient intakes. In contrast, real-world dietary restrictions can lead to nutritional deficiencies and heightened physiological stress that may worsen depressive symptoms.

Moreover, researchers noted that weight cycling—losing and regaining weight—could also contribute to an increase in depressive symptoms. They posited that diets lacking in essential nutrients like carbohydrates and omega-3 fatty acids may adversely affect cognitive function, particularly in men who have increased nutritional needs.

Professor Sumantra Ray, a leading scientist in the field, emphasized the importance of understanding the relationship between dietary patterns and mental health. He pointed out that while the observed effect sizes are small, further investigation is warranted to uncover the nuances of diet and its psychological implications.

As the study underlines a growing concern over restrictive dieting, it calls for further research focused on dietary intake and its comprehensive effects on mental health, potentially guiding future dietary recommendations and interventions.