Mechanism Underlying the Weight Loss and Complications of Roux-en-Y Gastric Bypass. Review

Abstract

Various bariatric surgical procedures are effective at improving health in patients with obesity associated co-morbidities, but the aim of this review is to specifically describe the mechanisms through which Roux-en-Y gastric bypass (RYGB) surgery enables weight loss for obese patients using observations from both human and animal studies. Perhaps most but not all clinicians would agree that the beneficial effects outweigh the harm of RYGB; however, the mechanisms for both the beneficial and deleterious (for example postprandial hypoglycaemia, vitamin deficiency and bone loss) effects are ill understood. The exaggerated release of the satiety gut hormones, such as GLP-1 and PYY, with their central and peripheral effects on food intake has given new insight into the physiological changes that happen after surgery. The initial enthusiasm after the discovery of the role of the gut hormones following RYGB may need to be tempered as the magnitude of the effects of these hormonal responses on weight loss may have been overestimated. The physiological changes after RYGB are unlikely to be due to a single hormone, or single mechanism, but most likely involve complex gut-brain signalling. Understanding the mechanisms involved with the beneficial and deleterious effects of RYGB will speed up the development of effective, cheaper and safer surgical and non-surgical treatments for obesity.

Impaired Enterohormone Response Following a Liquid Test Meal in Gastrectomized Patients

“…In fact and as expected, TG patients reached satiation earlier than controls, with final ingestion of lower quantities of the liquid test meal [7]. …”

Good weight loss responders and poor weight loss responders after Roux-en-Y gastric bypass: clinical and nutritional profiles

“…In addition to changes in the anatomy of the digestive tract after RYGB, some researchs have demonstrated that there are physiological changes involved in complex gut-brain nutrient and neural signaling after surgery, such as the influence of some gastrointestinal hormones involved in the control of hunger and satiety, for example, increased secretion of Glucagon-like peptide-1 (GLP-1) and peptide YY, and decrease ghrelin, with their central and peripheral effects on glycaemia and food intake, affecting glucose homeostasis and weight control (20)(21)(22).…”

The effects of bariatric surgical procedures on the improvement of metabolic syndrome in morbidly obese patients: Comparison of laparoscopic sleeve gastrectomy versus laparoscopic Roux-en-Y gastric bypass

“…In the meta-analysis performed by Rausa et al (23) the reoperation rate after LRYGB was found to be 1.4-3.1%. In addition, serious complications of LRYGB include bleeding (1.4%), anastomotic stricture (1.4%), infection (1.0%), fistula (0.5%), internal hernia (1.1%), and port site hernia (1.0%) (24).…”