Background

Changes in taste preference for palatable stimuli have been reported following bariatric surgery. To investigate the reward-based neural mechanisms for such changes, we measured behavioral and neural responsiveness to varying concentrations of sugar and fat-containing tastants in patients before and 6 months after vertical sleeve gastrectomy (VSG; N=23) or Roux-en Y gastric bypass (RYGB; N=19), respectively.

Methods

Preoperatively, patients rated 12 taste stimuli of varying sugar and fat content on a visual analog scale, and underwent functional magnetic resonance imaging while randomly presented with : high fat, or high sugar or tasteless stimuli, or the patient’s preferred tastant. Body weight was assessed 6 months postoperatively, and correlated with BOLD responses centered on the ventral tegmental area (VTA; pFWE <0.05).

Results

Presurgical VTA BOLD responses to high fat, high sugar, or the preferred tastant negatively correlated with weight change at 6 months after undergoing RYGB. Subjects with lower VTA response to palatable stimuli prior to RYGB lost more weight than those who exhibited higher responses. Presurgical VTA BOLD responses did not correlate with postoperative body weight changes in patients who underwent VSG.

Conclusions

Exposure to high calorie, highly palatable foods decreases activation in reward-based brain regions in the obese. Anatomical and metabolic changes associated with RYGB may reset the processing of rewarding stimuli. Individuals with a dampened response to food in reward-based regions such as the VTA may be more likely to benefit from RYGB. Alterations in neural responsiveness to reward may correlate with behavior change and greater weight loss (supported by 1K23DK100559).