Nearly Half of BMI Variance Is Explained by Personality Traits: A Multi-Method Study of Personality, Eating Behaviour, and Body Mass Index

Abstract

Previous research has shown that personality traits are associated with eating behaviour and body mass index (BMI), but these findings are often based only on self-reports. The present study investigated the associations between personality, eating behaviour, and BMI using combined self- and informant-reports from Estonian Biobank. Personality was assessed with the 100 Nuances Personality Questionnaire and eating behaviour with five eating behaviour items. Combining self- and informant reports (N = 15 571), correlations were calculated at domain and nuance levels. Structural equation modelling was applied to examine the predictive and mediating roles of personality and eating behaviour on BMI. Highest correlations between personality domains and eating behaviour were found for neuroticism (r = .16) and conscientiousness (r = −.24). However, stronger and more specific associations emerged at the nuance level, with effect sizes up to r = −.54. Higher BMI was most strongly associated with loss of control over eating (r = .53) and lower satiety responsiveness (r = −.48). In the structural equation models, personality (β = .50) and eating behaviour (β = .30) both significantly predicted BMI and explained 46.8% of its variance. Eating behaviour partially mediated the association between personality and BMI (20.23%). These findings suggest that combining self- and informant-reports helps reveal stronger and more precise links between personality, eating behaviour, and BMI.