Study Reveals Low-Calorie Diets May Increase Risk of Depression

Recent research published in the journal BMJ Nutrition Prevention & Health has established a connection between low-calorie diets and an increased risk of depressive symptoms. This investigation suggests that individuals, particularly men and those classified as overweight, may be more susceptible to the mental health impacts associated with restrictive eating patterns.

Generally, a diet characterized by minimally processed foods, including fruits, vegetables, whole grains, nuts, seeds, lean proteins, and fish, is linked with a reduced risk of depression. Conversely, a diet high in ultra-processed foods, refined carbohydrates, saturated fats, and sugars tends to correlate with a heightened risk of depressive symptoms.

This study utilized data from 28,525 adult participants (comprising 14,329 women and 14,196 men) from the US National Health and Nutrition Examination Survey (NHANES) conducted between 2007 and 2018. Participants completed the Patient Health Questionnaire-9 (PHQ-9), which assesses the severity of depressive symptoms.

Out of the total respondents, 2,508 individuals (approximately 8%) reported experiencing depressive symptoms. Among the participants, 7,995 (29%) were of healthy weight, 9,470 (33%) were classified as overweight, and 11,060 (38%) were considered obese.

Participants were questioned about their adherence to specific diets aimed at weight loss or other health issues. The dietary patterns were categorized into four groups: calorie-restrictive, nutrient-restrictive (low in fat, cholesterol, sugars, salt, fiber, or carbohydrates), established dietary patterns (such as those adapted for diabetes), and those not following any diet.

The majority of participants (25,009, or 87%) reported not adhering to any specific diet. In contrast, 2,026 (8%) followed a calorie-restrictive diet, 859 (3%) adhered to a nutrient-restrictive diet, and 631 (2%) were on an established dietary pattern.

Analysis of PHQ-9 scores indicated that individuals on calorie-restrictive diets had scores that were 0.29 points higher than those who were not following any particular diet. Among overweight participants adhering to calorie-restrictive diets, their PHQ-9 scores were elevated by 0.46 points, while those on nutrient-restrictive diets experienced a 0.61 point increase.

Additionally, calorie-restrictive diets were correlated with higher cognitive-affective symptom scores, which pertain to the relationship between thoughts and emotions. In contrast, nutrient-restrictive diets were associated with increased somatic symptom scores, reflecting excessive concern and anxiety regarding physical symptoms. Notably, these scores also varied by gender, with nutrient-restrictive diets leading to higher cognitive-affective symptom scores among men compared to women not adhering to a diet.

Individuals with obesity following established dietary patterns reported higher cognitive-affective and somatic symptom scores than those of healthy weight not on a diet. It is essential to note that this study is observational in nature, and therefore, it does not establish causality. The researchers caution that participants might not have accurately reported their dietary practices.

These findings present a divergence from previous research suggesting that low-calorie diets could enhance depressive symptoms. The researchers propose that this inconsistency may stem from earlier studies primarily involving randomized controlled trials (RCTs), where participants adhered to carefully structured diets ensuring balanced nutrition intake. In contrast, real-world calorie-restricted diets, particularly among those with obesity, often lead to nutritional deficiencies, which can heighten depressive symptoms, particularly affecting cognitive and emotional well-being.

Furthermore, the researchers speculate that factors such as weight cycling--losing and regaining weight--could contribute to these adverse psychological outcomes.

In discussing the gender discrepancies observed in the study, the researchers highlight the importance of glucose and omega-3 fatty acids for optimal brain health. They suggest that diets low in carbohydrates or fats may adversely affect cognitive function, particularly in men who may have greater nutritional requirements.

Professor Sumantra Ray from the NNEdPro Global Institute for Food, Nutrition and Health, co-owner of the journal, commented on the significance of this study in linking dietary patterns to mental health. He emphasized the need for more comprehensive studies that accurately capture dietary intake and mitigate the effects of confounding variables to further this important area of research.