Abstract
Motivation theories of obesity suggest that one of the brain mechanisms underlying pathological eating and weight gain is the dysregulation of dopaminergic circuits. While these dysregulations occur likely at the microscopic level, studies on gray matter volume reported macroscopic differences associated with obesity. One region suggested to play a key role in the pathophysiology of obesity is the nucleus accumbens (NAcc). We performed a meta‐analysis of findings regarding NAcc volume and overweight/obesity. We additionally examined whether gray matter volume in the NAcc and other mesolimbic areas depends on the longitudinal trajectory of obesity, using the UK Biobank dataset. To this end, we analysed the data using a latent growth model, which identifies whether certain variables of interest (e.g. NAcc volume) is related to another variable's (BMI) initial values or longitudinal trajectories. Our meta‐analysis showed that, overall, NAcc volume is positively related to BMI. However, further analyses revealed that the relationship between NAcc volume and BMI is dependent on age. For younger individuals such relationship is positive, while for older adults it is negative. This was corroborated by our analysis in the UK Biobank dataset, which includes older adults, where we found that higher BMI was associated with lower NAcc and thalamus volume. Overall, our study suggests that increased NAcc volume in young age might be a vulnerability factor for obesity, while in the older age decreased NAcc volume with increased BMI might be an effect of prolonged influences of neuroinflammation on the brain.
