Background: Obesity has been linked with subtle differences in brain structure. These differences tend to be especially relevant in prefrontal cortex regions, areas which play an important role in executive control. However, results in this field are often contradictory: although studies tend to report lower gray matter volume in relation to obesity, some have also observed null or positive associations. To overcome this issue, we conducted a meta-analysis on voxel-based morphometry (VBM) differences associated with obesity-related variables and validated the findings with an independent dataset.
Methods: The literature search included combinations of the following key words: (i) neuroimaging terms: MRI, gray matter, brain, magnetic resonance; (ii) obesity-related terms: obesity, obese, body mass, waist circumference, adiposity. We conducted the meta-analysis using Anisotropic Effect-Size Seed-Based d Mapping (AES-SDM) software. Twenty-one studies on obesity and VBM fulfilled our inclusion criteria, representing 5882 participants (54% females) aged 18-92 years. To examine the validity of our meta-analytic results, we additionally tested on an independent dataset (Human Connectome Project, n = 378 participants) whether mean VBM values obtained for each cluster showed correlations with body mass index (BMI).
Results: We found that obesity-related variables were consistently associated with lower gray matter volume in areas including the medial prefrontal cortex, bilateral cerebellum, and left temporal pole. The clusters showed negative associations between gray matter volume and BMI in the independent dataset, with the exception of one cluster in the cerebellum.
Conclusions: Our findings provide robust evidence that obesity and body mass are related to significantly lower gray matter volume in brain areas with a key role in executive control. These findings might suggest a neurobiological link between obesity and self-regulatory deficits.