Restrained eating was associated with higher levels of depressive symptoms, particularly in biological men and adults with elevated body mass index, according to findings from a UK-based study of 1,896 participants.

Researchers analyzed self-reported data using validated questionnaires to measure dietary restraint and depressive symptoms. While women reported higher average levels of restraint and depressive symptoms, men had a higher beta coefficient for the restraint-depression association (1.57 vs 0.82). Both associations were statistically significant (P < .001). 

"Men have higher nutritional requirements, making them more susceptible to deficiencies when adopting any restrictive diet," author Gabriella Menniti, of the University of Toronto, explained with colleagues. "Deficiencies in essential nutrients (eg, vitamin B12, folate and iron) can impair energy metabolism, exacerbating somatic symptoms of depression."

The authors further described the effects that glucose and omega-3 fatty acids can have on mood: "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." 

Body mass index also moderated the association. Among participants with elevated body mass index over 25, the association was stronger (β = 1.13) compared with those whose BMI was in the normal range (β = 0.80). Elevated BMI was reported by 67.1% of participants based on self-reported height and weight. Higher BMI from dietary choices was also connected to male participants, the authors noted. Men often prefer fatty meals, snack on sweets, and frequent fast-food restaurants more than women. Previous research demonstrated that men may also be less likely to believe that they need dietary changes.

Dietary restraint was measured using the 10-item Restraint subscale of the Dutch Eating Behaviour Questionnaire. Depressive symptoms were assessed using the Patient Health Questionnaire-9 (PHQ-9). The mean PHQ-9 score was 6, which indicated mild depressive symptoms. About 20.4% of participants scored 10 or higher, which was consistent with moderate to severe depression.

Women comprised 74.1% of the sample and reported higher average restraint and PHQ-9 scores than men. However, men showed a stronger statistical association between restraint and depression.

Older age and higher education were associated with lower depressive symptoms, though these factors did not significantly modify the restraint-depression relationship.

The study's cross-sectional design limited causal inference. Participants were recruited through a UK university and a crowdsourced online platform. Most (93.7%) were White and based in the UK. Limitations included reliance on self-reported data and a demographically skewed sample. 

The researchers noted that future longitudinal studies are needed to clarify causality and to explore these associations in more diverse, real-world populations, considering that adherence to diets may be higher in controlled trials than in everyday life, where restrictive eating may lead to the nutritional deficiencies the researchers described. They also noted "the need for studies examining realistic calorie-restricted diets with their potential nutritional deficiencies" as another contributing factor to depressive symptoms. 

Disclosures can be found in the published study.

Source: BMJ Journals