Mental health consequences of dietary restriction: increased depressive symptoms in biological men and populations with elevated BMI.

abstractIntroduction: The literature primarily examines the mental health effects of dietary patterns, with 'healthy' diets linked to fewer depressive symptoms, although no standardised definition of a 'healthy' diet exists. Many individuals adopt restrictive diets such as caloric or nutrient restriction or medically prescribed patterns (eg, diabetic diets) to improve health, yet their impact on depressive symptoms remains understudied. This study aims to evaluate the association between restrictive dietary patterns and depressive symptoms stratified by sex and body mass index (BMI). Methods: A cross-sectional study was performed using the National Health and Nutrition Examination Survey (NHANES) 2007-2018. Adults who completed dietary assessments and the Patient Health Questionnaire-9 (PHQ-9) for depressive symptom severity were included. Statistical analyses were performed using R. Multivariable linear regression was used to examine associations, and interaction effects were explored by including BMI or sex, with subgroup analysis performed when appropriate. Results: The study included 28 525 adults, of whom 7.79% reported depressive symptoms. Compared with individuals not following a specific diet, those adhering to calorie-restrictive diets had a 0.29 point increase in PHQ-9 scores (95% CI 0.06 to 0.52). Among overweight individuals, calorie-restricted diets were associated with a 0.46 point increase (95% CI 0.02 to 0.89) and nutrient-restricted diet was associated with a 0.61 point increase (95% CI 0.13 to 1.10) in PHQ-9 scores. Men who followed any diet showed higher somatic symptom scores than those not on a diet. Additionally, men on a nutrient-restrictive diet had a 0.40 point increase in cognitive-affective symptom scores (95% CI 0.10 to 0.70) compared with women not following a diet. Conclusions: There are potential implications of widely followed diets on depressive symptoms, and a need for tailored dietary recommendations based on BMI and sex.