Recent research published in the prestigious journal BMJ Nutrition Prevention & Health reveals compelling evidence that calorie-restrictive diets might be linked to an increased risk of depressive symptoms, particularly among biological men and individuals with elevated body mass index (BMI). This large-scale observational study uncovers nuances in the mental health consequences of various dietary restrictions, challenging previously held assumptions about the benefits of low-calorie diets on psychological well-being. The findings underscore the complex interplay between nutrition, metabolic health, and mental health in real-world settings.
Over the past decades, nutritional science has recognized the protective effects of ‘healthy’ diets rich in whole, minimally processed foods—including fresh fruits and vegetables, whole grains, nuts, seeds, lean proteins, and fish—against depressive disorders. Conversely, diets dominated by ultra-processed foods, refined carbohydrates, saturated fats, processed meats, and sweets have been consistently associated with heightened risk of depression. Despite this knowledge, many individuals adopt diverse dietary patterns for weight management or medical reasons that involve calorie or nutrient restriction, yet the mental health impacts of these diets have remained unclear until now.
To address this gap, researchers analyzed data from 28,525 adult participants in the United States National Health and Nutrition Examination Survey (NHANES) collected between 2007 and 2018. Participants completed the Patient Health Questionnaire-9 (PHQ-9), a standardized tool designed to quantify depressive symptom severity. This comprehensive dataset allowed investigators to examine associations between specific diet categories and depressive symptoms while controlling for demographic variables such as sex and body weight status.
The analyzed cohort consisted of nearly equal numbers of men (14,196) and women (14,329), with a notable prevalence of overweight (33%) and obesity (38%). Importantly, the participants self-reported their adherence to nine predefined diet types, enabling the classification into four distinct dietary pattern groups: calorie-restrictive diets, nutrient-restrictive diets (aimed at reducing fat, cholesterol, sugar, salt, fiber, or carbohydrates), established dietary patterns (such as diabetes-adapted diets), and those not following any particular diet.
A remarkable 87% of participants reported no specific dieting regimen, highlighting that restrictive diets remain the minority choice in the general population. Among those who did report dieting, calorie restriction was the most prevalent (8%), especially common among individuals with obesity (12%) and overweight (8%). Nutrient-restrictive and established dietary patterns were less frequently utilized, further emphasizing the importance of scrutinizing the psychological consequences of calorie restriction in particular.
Analysis of PHQ-9 scores revealed that participants on calorie-restrictive diets experienced a statistically significant increase in depressive symptoms compared to those not on any diet. This association was especially prominent among overweight individuals, whose depressive symptom scores were elevated by almost half a point. Nutrient-restrictive diets also correlated with increased depressive symptoms overall, strengthening the argument that dietary restrictions—beyond simple calorie reduction—can influence mental well-being.
Delving deeper into the symptom domains, calorie-restrictive diets were consistently linked with heightened cognitive-affective symptoms, which encompass disturbances in mood, thought, and emotional processing. Conversely, nutrient-restrictive diets aligned more closely with elevated somatic symptoms, such as physical distress, anxiety about bodily sensations, and fatigue. Such differential impacts suggest that specific types of dietary restriction may affect distinct neuropsychological pathways.
Intriguingly, sex differences were prominent in the data. Men following nutrient-restrictive diets exhibited higher cognitive-affective symptom scores than women who were not dieting, and all forms of restrictive diets were associated with greater somatic symptoms in men. This observation points to possible sex-specific vulnerabilities, potentially driven by differential nutrient needs or metabolic responses, warranting further investigation into gender-sensitive dietary recommendations.
Obese individuals adhering to established dietary patterns—often medically prescribed to manage comorbidities—also demonstrated elevated cognitive-affective and somatic symptomatology compared to healthy-weight counterparts not on restrictive diets. This finding highlights that the burden of obesity compounded with dietary restrictions may intensify mental health challenges, revealing an intertwined relationship between physiological and psychological factors in these populations.
The nature of this research as an observational study precludes causal inference, and the authors acknowledge potential inaccuracies in self-reported dietary adherence. Nevertheless, the findings contrast sharply with earlier randomized controlled trials (RCTs) that often demonstrated mental health improvements following low-calorie diets. A plausible explanation posited by the authors is that RCTs involve carefully designed diets ensuring balanced nutrient intake, whereas real-world dieting may lead to nutritional deficits, physiological stress, and ultimately worsening of depressive symptoms.
Among several biological pathways considered, the researchers emphasize the critical roles of glucose and the omega-3 fatty acid in maintaining brain health. Given that calorie and nutrient restrictive diets often diminish the intake of carbohydrates and essential fats, these deficits may compromise neuronal function and exacerbate cognitive-affective symptoms, particularly in men who may have higher nutritional demands. Additionally, phenomena such as weight cycling—repeated loss and gain—may contribute to psychological distress and undermine the stability of mood regulation.
Professor Sumantra Ray, Chief Scientist and Executive Director of the NNEdPro Global Institute for Food, Nutrition and Health, underscored the significance of this study in highlighting the delicate balance between diet and mental health. He noted the emerging evidence linking restrictive diets low in nutrients significant for cognitive function, such as omega-3 fatty acids and vitamin B12, to increased depressive symptoms. However, he also cautioned about the modest effect sizes reported and the need for better-designed research that minimizes confounding variables and accurately captures dietary behaviors.
In light of this work, clinicians and nutritionists should approach dietary recommendations with heightened awareness of potential mental health consequences, especially when advocating for restrictive eating in men or individuals with high BMI. The study acts as a call to refine dietary interventions, ensuring they promote not only physical health improvements but also psychological resilience through adequate nutrient provision.
Future research directions must prioritize longitudinal designs and utilize objective dietary assessment tools in order to disentangle causality from association. Moreover, exploring mechanistic insights into how specific nutrient deficits impact neuropsychological pathways will be pivotal. The integration of sex-specific analyses promises to advance personalized nutrition strategies that safeguard both metabolic and mental well-being.
This study ultimately expands our understanding of the complex biopsychosocial matrix linking diet, obesity, sex, and mood disorders. As public health policies continue to advocate for nutritional guidance, incorporating mental health ramifications alongside physiological outcomes will be essential for holistic wellness promotion.
Subject of Research:
People
Article Title:
Mental health consequences of dietary restriction: increased depressive symptoms in biological men and populations with elevated BMI
News Publication Date:
3-Jun-2025
Web References:
http://dx.doi.org/10.1136/bmjnph-2025-001167
References:
BMJ Nutrition Prevention & Health, DOI: 10.1136/bmjnph-2025-001167
Keywords:
Obesity, Mental health, Depression, Diets
