Study Unveils Effect of Low-Calorie Diet on Mental Health

Following a low-calorie diet may be linked to a greater risk of depressive symptoms, particularly in men and those who are overweight, according to new research published in the open-access journal BMJ Nutrition, Prevention & Health. The findings challenge some earlier studies suggesting that calorie restriction can improve mood and mental well-being.

The study investigated whether different dietary patterns—especially those aimed at reducing calorie or nutrient intake—might be associated with depression. Researchers analyzed data from 28,525 adults (14,329 women and 14,196 men) who participated in the U.S. National Health and Nutrition Examination Survey (NHANES) between 2007 and 2018. All participants had completed the Patient Health Questionnaire-9 (PHQ-9), a standardized tool for assessing depressive symptoms.

Participants were asked if they followed any specific diet to lose weight or for health reasons. The diets were categorized into four groups: calorie-restrictive, nutrient-restrictive (such as low-fat or low-carb diets), established dietary patterns (like diabetes-specific diets), and no diet. Most respondents (87%) reported not following any particular diet, while 8% were on a calorie-restricted diet.

The results showed that PHQ-9 scores were 0.29 points higher in those following calorie-restrictive diets compared to those not on any specific diet. The association was even stronger in overweight individuals. Calorie-restrictive diets were also linked to higher cognitive-affective symptom scores, which measure the relationship between thoughts and feelings. Nutrient-restrictive diets, meanwhile, were associated with increased somatic symptom scores, such as anxiety and physical distress.

Gender differences were also observed. Men on nutrient-restrictive diets had higher cognitive-affective symptom scores than women not on a diet, and all diet types were associated with increased somatic symptoms in men.

The researchers caution that this is an observational study and cannot prove causation. Misclassification of diets by participants and other confounding factors may also have influenced the findings. However, they suggest that real-life calorie-restricted diets may lack essential nutrients and induce physiological stress, potentially worsening mental health.

The study concludes that while low-calorie diets are often promoted for physical health, their impact on mental health, especially in specific groups, deserves closer scrutiny.

Reference: Gabriella Menniti, Shakila Meshkat, Qiaowei Lin, Wendy Lou, Amy Reichelt, Venkat Bhat. Mental health consequences of dietary restriction: increased depressive symptoms in biological men and populations with elevated BMI. BMJ Nutrition, Prevention & Health, 2025; bmjnph-2025-001167 DOI: 10.1136/bmjnph-2025-001167