Counting calories might feel discouraging on its own, but new research suggests it could also raise the likelihood of developing depression.
According to findings published June 3 in BMJ Nutrition Prevention & Health, people who followed low-calorie diets reported higher levels of depressive symptoms than those who weren’t dieting at all. The data also showed that men and individuals with excess weight were especially sensitive to mood shifts linked to calorie restriction.
“Calorie-restricted diets were associated with higher depressive symptom scores, which contrasts with the findings of earlier controlled studies,” concluded a team led by senior researcher Dr. Venkat Bhat, an associate professor of psychiatry at the University of Toronto.
“Additionally, biological men and overweight individuals appear more vulnerable to the negative effects of restrictive eating,” the team added.
Researchers theorized that limiting calories may also deprive the brain of important nutrients needed to support mood stability.
The study analyzed health information from more than 28,500 adults who took part in the U.S. National Health and Nutrition Examination Survey between 2007 and 2018. Participants completed a questionnaire that assessed symptoms of depression and reported whether they were following any type of diet.
Overall, nearly 8% of those surveyed said they were experiencing symptoms of depression.
Researchers then grouped participants according to their dietary habits — including calorie-restricted diets, nutrient-specific diets that cut carbs or fats, and diets used to manage health conditions such as diabetes or heart disease.
About 87% of participants weren’t dieting at all, while 8% reported following a low-calorie diet, 3% followed a nutrient-restrictive diet, and 2% were adhering to a diet for medical reasons.
People limiting calories had higher depression symptom scores than those who weren’t dieting, the study found.
Among individuals with overweight, the association was even stronger: those on either a calorie-restricted or nutrient-restrictive diet showed the highest levels of depressive symptoms. Men, in general, also appeared more prone to mood changes when on any kind of diet.
These results run counter to earlier research suggesting that low-calorie diets might actually ease symptoms of depression.
“This discrepancy may arise because prior studies were primarily randomized controlled trials where participants adhered to carefully designed diets ensuring balanced nutrient intake,” the researchers noted.
In everyday settings, however, low-calorie eating patterns can lead to nutrient shortages and added stress, which may worsen mood. The brain relies heavily on glucose and fatty acids to function properly, the team explained.
“Diets low in carbohydrates (glucose) or fats (omega-3s) may theoretically worsen brain function and exacerbate cognitive-affective symptoms, especially in men with greater nutritional needs,” the team wrote.
Another possible factor: people may become discouraged if they don’t lose weight as expected, or if they regain weight after dieting, which could also contribute to depressive symptoms.
Dr. Sumantra Ray, chief scientist and executive director of the NNEdPro Global Institute for Food, Nutrition and Health in the U.K., reviewed the study. He said the research “adds to the emerging evidence linking dietary patterns and mental health, raising important questions about whether restrictive diets which are low in nutrients considered beneficial for cognitive health, such as omega-3 fatty acids and vitamin B12, may precipitate depressive symptoms.”
Still, Ray noted that the effects identified in the study were modest.
“Further well-designed studies that accurately capture dietary intake and minimize the impact of chance and confounding are needed to continue this important line of inquiry,” he said in a news release.
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