Abstract
Objective: Few studies have investigated sex differences in brain structure associated with body mass index (BMI), and the related findings are inconsistent. In this study, we aimed to investigate the effect of sex × BMI interactions on gray matter volume (GMV), and to determine the implications of any structural differences.Methods: The final sample comprised 653 participants (449 women) who were assessed using voxel-based morphology analysis of T1-weighted magnetic resonance images. We used the voxel-based morphometry (VBM) to build a multiple regression model to explore the association between BMI and GMV, and used analysis of variance (ANOVA) to explore the BMI × sex interaction on GMV. A subset of 410 participants (291 women) underwent whole brain resting-state functional connectivity (rsFC) analysis to investigate sex differences in the seed (interaction) region. The cluster with a significant effect in the previous ANOVA analysis was used as a seed.Results: A significant BMI × sex interaction was observed in the left anterior cingulate cortex (ACC), while GMV was negatively correlated with BMI in men but not in women. The rsFC between the left ACC and the caudate was lower in men than in women. Within the entire sample, the insula, caudate, and medial frontal cortex activities were negatively correlated with BMI while the cerebellum and postcentral gyrus activities were positively correlated with BMI.Conclusions: Our findings address the interaction effect of BMI and sex on GM alterations. We found that the GMV in men seemed to be more likely to change with BMI than women, and the left ACC may be the reason for the increase in BMI of men, but not women.
Highlights
There are potential sex differences in the associations between body mass index (BMI) and regional gray matter volume (GMV) in the human brain
After family-wise error (FWE) correction, the multiple regression model revealed that BMI was negatively associated with GMV in the following brain regions: the bilateral insula, bilateral caudate, right middle cingulate gyrus, and a large cluster in the medial frontal cortex, extending from the orbitofrontal cortex (OFC) to the anterior cingulate cortex (ACC)
The results of the two-way analysis of variance (ANOVA) revealed a significant interaction effect (FWE, P < 0.05, voxel level) of BMI × sex in the left ACC where GMV was negatively correlated with BMI among men but not women
Summary
There are potential sex differences in the associations between body mass index (BMI) and regional gray matter volume (GMV) in the human brain. In the studies which found sex differences, the brain regions with significant results were different. The gray matter (GM) ratio (which was defined as the percentage of the GMV divided by the intracranial volume, to normalize differences in head size) was negatively correlated with BMI in men but not in women. A voxel-based morphometry (VBM) study indicated that the GMV of some brain regions in men was positively (the bilateral inferior frontal gyri, posterior lobe of the cerebellum, frontal lobes, temporal lobes, thalami, and caudate heads) or negatively (the bilateral medial temporal lobes, anterior lobe of the cerebellum, occipital lobe, frontal lobe, precuneus, and midbrain) correlated with BMI, but not in women. In another study, Horstmann et al (2011) found a significant correlation between the GMV in the putamen and BMI, and a negative correlation between leptin levels and the GMV in the right dorsolateral prefrontal cortex (dPFC) in women only
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