The Effect of Sleeve Gastrectomy on Post-prandial Serum Bile Acids

This is a prospective study of meal-induced bile acid physiology before and after sleeve gastrectomy (SG) surgery. Weight loss and metabolic improvement associated with weight loss surgery cannot be entirely attributed to restriction in stomach size and food intake. Bile acids (BAs), amphipathic steroids that have a role in lipid uptake and metabolism in the gastrointestinal tract, are involved in post-prandial glucose homeostasis and energy expenditure \& are a potential intermediary in weight loss following bariatric surgery. It is unknown if SG increases post-prandial BAs in humans and if an increase in BA signaling impacts weight loss and co-morbidity resolution after surgery. The investigators hypothesis is that SG will increase the post-prandial serum and urine BAs and that the change in the BA profile is a mechanism for restriction-independent weight-loss following SG. SG patients will undergo a meal challenge pre-operatively, and at 1, 3, and 12 months post-operatively, with measurement of post-prandial serum and urine BAs and downstream hormones, glucagon-like peptide 1 (GLP-1) and fibroblast growth factor 19 (FGF19), and a scoring of satiety before and after the meal challenge using a Visual Analog Scale. Serum insulin, glucose, and C4 levels will also be measured to assess metabolic changes associated with SG. Serum and urine BA levels will be compared to post-operative excess weight loss at 12 months. Before and after each meal challenge, patients will be asked to score satiety, and this will be correlated to weight loss, bile acids, GLP-1, and FGF19.