Beyond BMI: Personality traits’ associations with adiposity and metabolic rate

Abstract

Various personality traits are known to correlate with body mass index (BMI). However, this index of adiposity conflates fat mass with lean body mass and may therefore lead to biased estimates of correlations. Yet, rarely have studies looked beyond BMI to understand how adiposity and other physiological characteristics relate to these psychological traits. Using previously validated formulas, we calculated an improved measure of adiposity (relative fat mass, RFM), as well as basal metabolic rate (BMR); explored their associations with various personality traits; and assessed how personality traits’ associations with RFM differ from their associations with BMI. In a subsample of the Estonian Biobank (N = 3535), we compared how the five domains and 30 facets of NEO Personality Inventory-3 correlated with RFM, BMI, and BMR. Various traits, notably Openness to Experience and its facets, were associated with RFM above and beyond BMI; these traits may relate to lower adiposity through eating habits. Assertiveness, a facet of Extraversion, correlated more strongly with BMI than with RFM and also correlated with BMR. These correlations mirror associations of metabolic rate with conceptually similar traits in non-human animals and are consistent with Assertiveness being based on biological processes. Finally, BMI–personality trait correlations appeared to conflate personality traits’ associations with fat mass and lean mass; the use of BMI as an indicator of adiposity can lead to both attenuated and inflated estimates of personality trait–adiposity associations.