Influence of feeding state on neurofunctional differences between individuals who are obese and normal weight: a meta-analysis of neuroimaging studies.

Obesity is a complex disorder associated with serious health risks. Examining differences in brain activity between normal weight and obese populations in response to food cues may help researchers and clinicians understand the underlying causes of overeating and obesity and help prevent them. Multiple neuroimaging studies have investigated weight differences in functional activity to food cues but have found varying results. We performed six meta-analyses of functional neuroimaging studies of weight differences in response to food images and isolated differences in processing between normal weight and obese participants. Within this study, 7 papers and 3 sets of unpublished data on functional activation to food images were analyzed using an Activation Likelihood Estimation meta-analytic approach. These analyses also addressed how feeding state impacts functional activity between weight groups. Feeding state affected weight related differences in neurofunctional activity triggered by visual food cues. In the premeal state, greater activation in the amygdala/hippocampus was found in obese participants compared to normal weight participants and, in the postmeal state, obese individuals had greater activation in the caudate and medial prefrontal cortex (MPFC) as compared to normal weight individuals. Regions of the brain associated with caloric evaluation, arousal, and memory were more active in the obese before eating, while less activity was found in an area linked to interoceptive processing. In the postmeal state, greater activity was found in the obese in areas related to risk vs. reward evaluation and reward processing. These findings may help researchers and clinicians understand and treat obesity related behaviors by identifying the altered functional regions that lead to obesity, providing a guide for future research on which neural regions need to be the target of further investigation.