Gastric bypass surgery alters food preferences through changes in the perception of taste

Editeur : Future Medicine ; ISSN: 2044-9038 ; ESSN: 2044-9046Roux-en-Y gastric bypass is one of the most effective treatments for morbid obesity as it results in long-term weight loss and significant remission of obesity-related comorbidities. Although it is successful in causing weight loss, the underlying mechanisms are not completely understood. A significant decrease in calorie intake related to a shift in food preferences towards lower-calorie-dense foods has been observed after the surgery. This modification in ingestive behavior occurs through changes in the sensory and reward domain of taste. Potential mediators of these taste modifications are the exaggerated levels of gut hormones or altered gut nutrient sensing. Understanding the molecular mechanisms involved in the Roux-en-Y gastric bypass-induced taste/food preference modifications would be crucialfor the development of 'knifeless' treatments. Obesity is a leading cause of death [101]. The comorbidities of obesity include cardiovascular disease, Type 2 diabetes mellitus, cancer, nonalcoholic fatty liver disease, arthritis and infertility, among others [1-6]. Roux-en-Y gastric bypass (RYGB) is one of the most effective treatments for morbid obesity [7], resulting in long-term weight loss maintenance, significant remission of obesity-related comorbidities [8-10] and decreased overall mortality [10]. RYGB results in five main anatomical changes: Reduction of the stomachize (15-30 ml), leaving a large stoma to allow food rapid passage between the esophagus and midgut; Food bypassing the stomach and the first part of the proximal small bowel; Altered bile flow through the same proximal small bowel; Anastomosis of the midgut to the stomach, allowing earlier contact of food with the distal small bowel; Disruption of vagal fibers across the stomach, while leaving the main branches of the vagus intact. Although the RYGB procedure is successful in causing weight loss, the relevant mechanisms are not completely understood. Even though the procedure was originally designed to cause restriction, the flow of food is accelerated from the esophagus to the midgut through the large gastro-jejunostomy [11]. Calorie malabsorption does not play a physiologically significant role as fecal fat and calorie loss is minimal, while many patients actually report constipation after RYGB [11,12]. Significant increase in energy expenditure have been reported after RYGB in animals [6,13-15] and in one study in humans [16] but this change may be triggered by changes in body composition. However, one study has shown that diet-induced thermogenesis of multiple meals results in an overall increase in 24-h energy expenditure compared with a group of patients that lost the same amount of weight with a vertical-banded gastroplasty [16]. Significant decrease in calorie intake has also been reported after the surgery in humans [17,18]. The decrease in total calorie intake is related to reductions in hunger, increases in satiety, changes in meal patterns, in addition to a shift in food preferences towards lower-calorie-dense foods [18-22]. Here, we review the changes in eating behavior after RYGB, and focus on potential mechanisms underlying this shift, including changes in quantitative taste identification and taste ingestive motivation (reward). Finally, we explore potential mediators underlying this mechanism, such as gut hormones or nutrient sensing