A large new study suggests that following a low-calorie diet may increase the risk of experiencing depressive symptoms, especially in men and people who are overweight or obese.
The research, published in BMJ Nutrition, Prevention & Health, found that restrictive eating in real-life settings could have emotional downsides, even though such diets are often promoted for weight loss and health improvement.
Researchers looked at data from 28,525 U.S. adults who participated in the National Health and Nutrition Examination Survey (NHANES) between 2007 and 2018.
These participants had completed a standard mental health questionnaire, the PHQ-9, which assesses the severity of depressive symptoms. The average age was around 50, and nearly half of the group was classified as overweight or obese.
The study divided participants into four groups: those not on a diet, those following a calorie-restrictive diet (eating fewer calories), those on a nutrient-restrictive diet (limiting fat, sugar, salt, fiber, or carbs), and those following a medically established dietary plan, such as a diet for diabetes.
The results showed that people on calorie-restrictive diets had slightly higher depression scores than those not on any diet. For people who were overweight and also dieting, the scores were even higher. Nutrient-restrictive diets were linked to even greater increases in depression scores.
These findings were particularly noticeable in men, who reported more emotional (cognitive-affective) and physical (somatic) symptoms than women following similar diets.
Interestingly, people with obesity who were following medically recommended diets also showed more signs of emotional and physical distress compared to healthy-weight individuals not on any diet.
Although earlier clinical trials have suggested that carefully planned low-calorie diets can actually reduce symptoms of depression, the researchers explain that the real-world picture may be very different.
Unlike controlled trials, where diets are designed by professionals to ensure proper nutrition, many people attempting calorie restriction on their own may end up with unbalanced diets that lack important nutrients such as protein, vitamins, minerals, and healthy fats. These deficiencies could lead to increased stress and mood problems, especially over time.
The researchers also point out that repeatedly losing and regaining weight—a pattern known as weight cycling—may contribute to depression, particularly when weight loss goals are not met.
The study does not prove that dieting causes depression. As an observational study, it can only show associations. People who are already feeling down might be more likely to go on restrictive diets, or they may struggle more with sticking to them, which can affect their mood. There’s also the possibility that participants didn’t accurately report what kind of diet they were on.
Still, the research raises important questions. Certain nutrients, such as carbohydrates (glucose) and omega-3 fatty acids, are known to be essential for brain health. Diets too low in these nutrients—especially in men, who may have higher nutritional needs—could theoretically impair brain function and increase the risk of depressive symptoms.
Professor Sumantra Ray of the NNEdPro Global Institute for Food, Nutrition and Health, who was not involved in the study, cautioned that the actual increase in depression scores was small and that more rigorous research is needed. However, he noted the findings add to growing evidence linking diet and mental health.
In short, while calorie control can be useful for managing weight and certain health conditions, this study suggests that restrictive diets—especially poorly planned ones—may come with mental health risks.
Anyone considering a low-calorie or nutrient-restrictive diet should talk to a healthcare provider or dietitian to ensure their diet is balanced and supportive of both physical and emotional well-being.
If you care about mental health, please read studies about 6 foods you can eat to improve mental health, and B vitamins could help prevent depression and anxiety.
For more health information, please see recent studies about how dairy foods may influence depression risk, and results showing Omega-3 fats may help reduce depression.
The research findings can be found in BMJ Nutrition Prevention & Health.
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