Selective Reduction in Neural Responses to High Calorie Foods Following Gastric Bypass Surgery

Abstract

Objective To investigate changes in neural activation and desire to eat in response to appetitive cues from pre- to postbariatric surgery for obesity. Background Roux-en-Y gastric bypass (RYGB) is the most common bariatric procedure. However, the mechanisms of action in RYGB are not well understood. A significant proportion of the resulting reduction in caloric intake is unaccounted for by the restrictive and malabsorptive mechanisms and is thought to be mediated by neuroendocrine function. Numerous investigations of postsurgical changes in gut peptides have resulted; however, changes in neural activation after RYGB surgery have not been previously investigated. Methods Functional magnetic resonance imaging and verbal rating scales were used to assess brain activation and desire to eat in response to high-and low-calorie food cues in 10 female patients 1-month pre- and post-RYGB surgery. Results Postsurgical reductions in brain activation were found in key areas within the mesolimbic reward pathway, which were significantly more pronounced in response to food cues that were high (vs. low) in caloric density. These changes mirrored concurrent postsurgical reductions in desire to eat, which were also greater in response to food cues that were high versus low in caloric density (P = 0.007). Conclusions Findings support the contention that RYGB surgery leads to substantial changes in neural responses to food cues encountered in the environment, provide a potential mechanism for the selective reduction in preferences for high-calorie foods, and suggest partial neural mediation of changes in caloric intake seen after RYGB surgery.

Elevated Postoperative Endogenous GLP-1 Levels Mediate Effects of Roux-en-Y Gastric Bypass on Neural Responsivity to Food Cues

“…Postoperative neuroendocrine alterations are suggested to play an important role in these effects of RYGB (21). Decreased activations in areas that are part of the central reward circuits (among others, ventral striatum and putamen) in response to visual food cues after RYGB have been described (6,7). RYGB is also associated with a deceased desire to eat highly palatable food (6,22).…”

“…Decreased activations in areas that are part of the central reward circuits (among others, ventral striatum and putamen) in response to visual food cues after RYGB have been described (6,7). RYGB is also associated with a deceased desire to eat highly palatable food (6,22). In accordance with these studies, we observed decreased CNS activation in response to both visual and gustatory food cues after RYGB, paralleled by decreased scores for hunger and appetite.…”

“…Altered responses to visual and gustatory food cues have indeed been described in obese individuals, using functional MRI (fMRI) (3)(4)(5). Interestingly, weight loss after RYGB is paralleled by decreased responsivity of the CNS to high-calorie visual food cues, measured with fMRI (6,7), which may contribute to the reduced hedonic drive to consume highly palatable food and therefore contribute to the substantial weight loss after RYGB. However, the mechanism explaining this altered CNS responsivity to food cues after RYGB is unknown.…”

Neuronal Food Reward Activity in Patients With Type 2 Diabetes With Improved Glycemic Control After Bariatric Surgery

“…Similarly, Bruce et al (39) reported that patients who had undergone gastric banding surgery showed higher inferior frontal activity during the processing of food pictures before than after surgical intervention. In addition, changes in food reward-related brain regions were reported soon after bariatric surgery (24) and after a weight loss of at least 8% (40). The globus pallidus is proposed to directly initiate reward-related signals (41).…”

“…On a neuronal level, bariatric surgery results in altered neuronal responses to food cues, particularly in the reward, gustatory, and homeostatic regions (11,(24)(25)(26). A comparison of neuronal responses to food items between patients postsurgery and a lean and an obese control group showed that severely obese women who underwent RYGB at least 1 year earlier showed a normalization of obesity-associated alterations in brain activity (25).…”