Neural Mechanisms of Affective Processing in Obesity and Associations with Weight Loss

Obesity affects over one-third of the American population and is associated with a myriad of physiological and psychological health concerns. While obesity has a number of contributing factors, the most prevalent is consumption of food beyond caloric need. Thus, valuation of salient external stimuli is implicated, as well as approach- and avoidance behavior. These occur through affective processing, which drives an individual’s valuation and orientation toward valenced stimuli. Affective processing abnormalities in individuals with obesity have been shown in the context of food, as well as other stimuli, including facial expression of emotion. However, to date, a direct comparison between facial affective processing in individuals with obesity and lean controls, as well as in individuals with obesity before and after weight loss, has not been examined. To that end, we used a facial affective processing task in a functional magnetic resonance imaging experiment to identify differences in affective processing between lean participants and participants with obesity, as well as participants with obesity before and after significant weight loss. We found that lean individuals demonstrated greater bilateral insula activation when viewing neutral faces compared to affective faces, while participants with obesity demonstrated greater dorsolateral prefrontal cortex activity when viewing neutral faces compared to affective faces. Additionally, participants with obesity demonstrated increased functional connectivity within the affective network while viewing affective faces. However, there was no difference in affective processing in participants with obesity after weight loss. These results indicate that lean controls may demonstrate increased uncertainty and attention to neutral faces in an attempt to decipher unexpressed emotion, while participants with obesity may demonstrate greater executive control, perhaps in the maintenance of attention to faces without emotion expression. In conclusion, these results suggest differences in affective processing between participants with obesity and lean controls, and a lack of change in affective processing after weight loss. These results may help guide future treatment options for obesity, particularly incorporating affective processing.