Intelligence and Personality as Predictors of Body Mass Index: A Longitudinal Twin Study

Sammanfattning

Unhealthy Body Mass Index (BMI) levels at both ends of the weight spectrum remain a public health concern despite widespread interventions. This ongoing problem points to the importance of understanding the factors that shape BMI beyond behavior and lifestyle alone. The present study therefore investigated the genetic influences on BMI and the predictive roles of intelligence and personality in shaping individuals’ BMI levels. A subsample of the German TwinLife study was utilized and the analyses included 2,044 monozygotic and dizygotic twin pairs assessed twice over a two-year period. The first analyses involved univariate and multivariate twin models to examine the environmental and genetic influences on BMI, intelligence and Five Factor model (FFM) personality traits. In a further extension, linear regression models were used to assess the predictive effects of intelligence and FFM personality traits on BMI. The results from the twin models confirmed that BMI, intelligence and FFM personality traits are heritable to a high extent. The linear regression models found intelligence, agreeableness and extraversion to be significant predictors of BMI levels at baseline, with intelligence as the only significant longitudinal predictor of BMI levels (β = -.05). While most findings were in line with previous research, conscientiousness was not found to be predictive of BMI levels, an unexpected finding due to its predictive power in previous studies. Future directions are suggested and discussed, with emphasis on the need for more reliable measurements of key variables.