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In an elegant, well-conducted and uniquely multidimensional study, Scholtz et al1 used functional MRI (fMRI) to demonstrate that (morbidly) obese patients after Roux-en-Y gastric bypass (RYGB) show significantly lower responses to high-calorie food images in the reward system of the brain, compared with non-operated obese controls and obese patients after gastric banding. The RYGB group also rated the high-calorie food images as less appealing (anticipatory reward, ‘wanting’) and the subsequent ice cream lunch as less pleasant to eat (consummatory reward, ‘liking’). Further, the energy intake derived from fat as well as scores for restraint and external eating were lower in the RYGB group. Finally, these changes were accompanied by higher levels of the anorexigenic gut peptides glucagon-like peptide 1 and peptide YY, as well as bile acids, and lower levels of insulin during presentation of the images and/or meal intake.
This study adds significantly to an emerging body of literature on the key role of the brain's reward system in the control of food intake in health and obesity. The mesolimbic reward system has evolved in evolution to select and reinforce adaptive behaviour that serves to obtain ‘natural’ rewards crucial for survival, including food, in close interplay with homoeostatic circuits processing information on the metabolic state of the body. Although it may be a bridge too far to label all obese patients without any distinction as suffering from ‘food addiction’,2 on conceptual and empirical grounds, recent evidence does support …