Higher Adolescent Body Mass Index Is Associated with Lower Regional Gray and White Matter Volumes and Lower Levels of Positive Emotionality

Abstract

Adolescent obesity is associated with an increased chance of developing serious health risks later in life. Identifying the neurobiological and personality factors related to increases in adiposity is important to understanding what drives maladaptive consummatory and exercise behaviors that result in obesity. Previous research has largely focused on adults with few findings published on interactions among adiposity, brain structure, and personality. In this study, Voxel Based Morphometry (VBM) was used to identify associations between gray and white matter volumes and increasing adiposity, as measured by Body Mass Index percentile (BMI%), in 137 adolescents (age range: 9-20 years, BMI% range: 5.16-99.56). Variations in gray and white matter volume and BMI% were then linked to individual differences in personality measures from the Multidimensional Personality Questionnaire (MPQ). After controlling for age and other covariates, BMI% correlated negatively with gray matter volume in the bilateral caudate (right: partial r = -0.338, left: r = -0.404), medial prefrontal cortex (partial r = -0.339), anterior cingulate (partial r = -0.312), bilateral frontal pole (right: partial r = -0.368, left: r = -0.316), and uncus (partial r = -0.475) as well as white matter volume bilaterally in the anterior limb of the internal capsule (right: partial r = -0.34, left: r = -0.386), extending to the left middle frontal subgyral white matter. Agentic Positive Emotionality (PEM-AG) was correlated negatively with BMI% (partial r = -0.384). PEM-AG was correlated positively with gray matter volume in the right uncus (partial r = 0.329). These results suggest that higher levels of adiposity in adolescents are associated with lower trait levels in reward-related personality domains, as well as structural variations in brain regions associated with reward processing, control, and sensory integration.

Keywords: BMI; adolescence; obesity; personality; voxel based morphometry.

Figure 1

Clusters where gray matter densities are negatively associated with BMI% shown in blue. ACC, Anterior cingulate cortex. VBM clusters overlaid onto the gray matter DARTEL warp template. Centered on MNI Coordinates 13, 58, 11. FWE-corrected p-values shown from 0.001 (light blue) to 0.05 (dark blue).

Figure 2

Clusters where white matter densities are negatively associated with BMI% shown in blue. ALIC, Anterior limb of the internal capsule. MFG, Middle frontal gyrus. VBM clusters overlaid onto the white matter DARTEL warp template. Centered on MNI Coordinates −24, 7, 17. FWE-corrected p-values shown from 0.001 (light blue) to 0.05 (dark blue).

Figure 3

Regression plots showing associations between BMI%, uncus gray matter volume, and Agentic Positive Emotionality (all variables centered). (A) Regression of BMI% on uncus gray matter volume (controlling age, sex, the interaction of BMI% and age, and global gray matter), partial r = −0.475, p < 0.001. (B) Regression of uncus gray matter volume on Agentic Positive Emotionality (controlling age, sex, and global gray matter), partial r = 0.320, p = 0.001. (C) Regression of Agentic Positive Emotionality on BMI% (controlling age and sex), partial r = −0.384, p < 0.001.