Personality traits and body mass index: Modifiers and mechanisms

OBJECTIVE: To identify how demographic factors (sex, age, ethnicity) modify the association between personality traits and body mass index (BMI) and to test the extent that diet and physical activity account for the personality-BMI relations. DESIGN: Cross-sectional study with a diverse sample (N = 5150, 50% female, 19% African American, 15% Hispanic). Participants completed a measure of the five major dimensions of personality and reported on their physical activity, diet and food intake behaviour, and height and weight. MAIN OUTCOME MEASURES: BMI and obesity (BMI ≥ 30). RESULTS: High Neuroticism was associated with higher BMI and risk for obesity, whereas Conscientiousness and, to a lesser extent, Extraversion and Openness were protective. These associations were generally stronger among women and older participants; there was less evidence for ethnicity as a moderator. Personality had similar relations with the behavioural factors, and physical activity, diet and regular meal rhythms accounted for approximately 50% of the association between Neuroticism and Conscientiousness and BMI. CONCLUSION: This study supports the links between personality traits and BMI and suggests that physical activity, more than diet, is a key factor in these associations.