Gastrointestinal Endocrinology in Bariatric Surgery.

The long-lasting weight-reducing effect of bariatric surgical procedures cannot simply be explained by the malabsorption of nutrients and the subsequent energy deficit due to this malabsorption. Clinical studies have shown that the reorganization of the anatomy of the gut and the subsequent alterations of gastrointestinal physiology have a large impact on the secretion and function of gastrointestinal hormones, which regulate hunger and satiety. These changes have been named the BRAVE effect: bile flow alteration, reduction of gastric size, anatomical gut rearrangement and altered flow of nutrients, vagal manipulation, and enteric gut modulation. In addition, the metabolic improvements, for example, increased insulin secretion and improved glucose sensitivity after bariatric surgery cannot simply be explained by the weight loss achieved by the operation. Several metabolic improvements occur directly after bariatric surgery even before significant weight loss has occurred. Clinical studies revealed that the altered gastrointestinal physiology and the postoperative profile of gastrointestinal hormones are responsible for these metabolic alterations. Further insights into the changes of gastrointestinal hormone profiles before and after bariatric surgery may open new ways to prevent the surgical procedure and probably obtain equivalent results by nutraceuticals.