Low-calorie diets linked to increased risk of depression, especially in men and people living with obesity
Key Takeaways:
- Low-calorie diets may increase the risk of depressive symptoms, particularly among men and people living with overweight or obesity, according to a large population study.
- Nutritional deficiencies linked to unsupervised calorie restriction may negatively affect mental wellbeing, highlighting the importance of dietary quality.
- The findings challenge previous clinical studies suggesting mood benefits from calorie restriction, calling attention to the gap between controlled interventions and real-world dieting behaviour.
Introduction
Restrictive dieting is a common approach to weight management, but emerging evidence suggests that cutting calories—especially without professional guidance—may have unintended consequences for mental health. A new Canadian study published in BMJ Nutrition, Prevention & Health has found a link between low-calorie diets and an increased risk of depressive symptoms, particularly among men and individuals living with overweight or obesity.
Study Overview
Researchers analysed data from 28,525 adults who took part in the US National Health and Nutrition Examination Survey (NHANES). Participants completed a standardised mental health questionnaire, which assessed symptoms such as persistent low mood, fatigue, and disturbed sleep.
The study revealed that individuals who were actively restricting their calorie intake scored higher for depressive symptoms than those who were not dieting. The association was especially pronounced among:
- Men
- People classified as having overweight or obesity
Overall, around 8% of participants reported symptoms of depression, while over 70% were living with overweight or obesity—a demographic more likely to engage in calorie-restrictive dieting.
The Role of Nutritional Deficiency
While the study could not prove causation, the researchers proposed that self-imposed dietary restrictions may lead to insufficient intake of essential nutrients—particularly protein, vitamins, and minerals. Such deficiencies can place the body under physiological stress, potentially exacerbating or triggering symptoms of poor mental health.
This stands in contrast to earlier clinical trials where calorie-restricted diets appeared to improve mood. However, the authors of the current study point out that these prior interventions were typically nutritionally balanced and closely monitored, unlike the unsupervised and potentially imbalanced dieting patterns seen in the general population.
Diet Quality Matters
The study draws a distinction between restrictive dieting and overall dietary quality. Diets that are rich in whole foods—including fruits, vegetables, whole grains, nuts, and lean protein—have consistently been associated with lower rates of depression. In contrast, those high in ultra-processed foods and refined carbohydrates are linked to higher depression risk.
Expert Commentary
Professor Sumantra Ray, Executive Director of the NNEdPro Global Institute for Food, Nutrition and Health, underscored the wider implications of the findings:
“This adds to the growing body of evidence linking diet and mental health.
Restrictive diets low in nutrients important for cognitive function, such as omega-3 and vitamin B12, may contribute to depressive symptoms. However, further well-designed studies are needed to better understand these relationships.”
Implications for Healthcare Practice
While the study is observational and cannot confirm a causal relationship, it offers a timely reminder for healthcare professionals. When supporting individuals who wish to lose weight, especially those with existing vulnerabilities to depression or anxiety, it is crucial to:
- Emphasise nutritional adequacy, not just calorie reduction
- Support patients in choosing sustainable, balanced dietary patterns
- Consider mental health screening as part of weight management strategies
In summary, the findings call for a more nuanced approach to dietary advice—one that respects the complex interplay between physical and mental health, and avoids simplistic calorie-cutting recommendations that may do more harm than good.
