Neuroimaging studies have identified obesity-related alterations in the brain’s reward and inhibitory networks, which may contribute to overeating. The rate of obesity-related diseases is 6.6 times greater in women than in men, and overweight women have twice the risk of mortality compared to overweight men. Since neuroimaging studies offer insight regarding the brain’s response to emotion and food-related stimuli, the aim of this study was to conduct a meta-analysis to quantify sexually dimorphic brain signatures using stimulus-based functional MRI studies related to obesity.
PubMed, Web of Science, and PsycINFO databases were searched using a list of keywords related to obesity, functional magnetic resonance imaging, and sex/gender. After three stages of screening, studies included (N=64) used a stimulus during fMRI (e.g. viewing food cues). Comparisons were made by disease and sex using an activation likelihood estimation meta-analytic approach.
Disease Differences: Obese individuals showed activation of regions within the reward network, whereas lean individuals showed activation of regions implicated in cognitive control, interoceptive awareness, and homeostatic processing. Sex-Differences: Females showed activation of reward regions, while males showed activation of executive control and somatosensory regions.
Consistent with the reward deficiency syndrome hypothesis, these results demonstrate increased activation in reward regions, but decreased activation in executive control regions suggesting that lower dopamine could be attributing to less sensitivity to reward stimuli and increased food intake. Differential sex- related activation was observed in these two networks, specifically greater activation in obese females in regions implicated in reward anticipation and response, forming food-related memories, and generating top-down control of appetitive processes. Together, these findings have implications for sex-specific obesity treatments.