A new study suggests that low-calorie diets may contribute to a slight rise in depressive symptoms, particularly in overweight individuals and men. The large observational study, published in BMJ Nutrition, Prevention & Health, analyzed the dietary habits and depression scores of more than 28,000 U.S. adults.
The findings show that people on calorie-restrictive diets reported higher levels of emotional and physical distress compared to those not following any diet. The study raises concerns about the potential negative effects of unsupervised restrictive diets on mental health in real-world settings.
Key Findings:
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Depression Risk: Those on calorie-restrictive diets had higher depression scores than those not dieting, based on the Patient Health Questionnaire (PHQ-9).
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Gender Differences: Men on restrictive diets had higher emotional and physical distress scores than women.
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Obesity Connection: Overweight and obese participants on restrictive diets experienced more pronounced depressive symptoms.
Research Overview
The study, based on data from the U.S. National Health and Nutrition Examination Survey (NHANES) from 2007 to 2018, involved 28,525 adults. These participants were asked about their diet habits and completed the PHQ-9 questionnaire to assess depression severity.
Out of the respondents, 2,508 (8%) reported depressive symptoms. Participants were categorized based on their diet into four groups: calorie-restrictive, nutrient-restrictive, established dietary patterns, and those not following a specific diet.
Most participants (87%) were not on any particular diet. Among those who were dieting, 8% followed a calorie-restrictive diet, 3% a nutrient-restrictive diet, and 2% followed an established dietary pattern.
Impact of Diet on Depression
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Calorie-restrictive Diets: These diets were associated with a 0.29-point higher PHQ-9 score. Overweight individuals on calorie-restrictive diets had a 0.46-point increase, while those on nutrient-restrictive diets had a 0.61-point higher score.
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Gender Disparities: Men on nutrient-restrictive diets showed higher cognitive-affective symptoms than women, indicating that men may be more affected by these diets.
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Obesity and Diet: Participants living with obesity who followed an established dietary pattern had higher emotional and physical distress scores than those with a healthy weight who were not on a diet.
Potential Explanations
While this is an observational study, the researchers suggest that restrictive diets may cause nutritional deficiencies and stress, which could worsen depressive symptoms. They also note that prior studies, particularly randomized controlled trials, may have shown different results due to more controlled environments with balanced nutrient intake.
The study further highlights that diets low in key nutrients such as omega-3 fatty acids and glucose might impact brain health, particularly in men who have higher nutritional needs. These factors could contribute to cognitive-affective symptoms and worsen depression.
Expert Opinion
Professor Sumantra Ray, Chief Scientist at the NNEdPro Global Institute for Food, Nutrition, and Health, commented that the study adds to the growing body of evidence linking diet and mental health. He emphasized the importance of further research to understand the role of nutrient deficiencies in mental health, particularly in relation to restrictive diets.
Despite the small effect sizes observed in this study, Ray called for more well-designed studies to explore these connections and their broader implications for public health.
Conclusion
The study underscores the need for caution when following restrictive diets without proper supervision. While some diets may promote weight loss, their impact on mental health—especially for those with existing vulnerabilities—should not be overlooked. Further research is needed to fully understand the long-term effects of these dietary patterns.
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