Gut hormones and leptin: impact on energy control and changes after bariatric surgery--what the future holds

Obesity is now considered the new world epidemic. In an attempt to face this menace to public health, several treatments, apart from the traditional nutritional modification and oral medication, have been introduced, among them bariatric surgery and gut hormone-based treatments. The gastrointestinal (GI) tract is a powerful endocrine organ, releasing active peptides and influencing appetite and glycaemic control. Alteration of the GI tract, in ways that exaggerate the secretion and levels of the gut hormones, creates a new functional equilibrium that further contributes to weight loss. The purpose of this review is to explore the mechanisms that drive this gut hormone-derived body regulation, as well as the changes that occur to them after bariatric surgery. Close to that, leptin, a hormone secreted by adipose tissue will be analysed, as its pathways are closely related to those of the gut hormones. Gut hormones are strongly implicated in energy control, and various effects of bariatric surgery in weight loss are directly related to the alteration of the levels of these hormones.