Mechanisms Responsible for Excess Weight Loss after Bariatric Surgery

Abstract

Obesity has increased alarmingly in the United States and is increasing in many countries of the world. Because obesity is an important risk factor for type 2 diabetes and other chronic diseases, it is important to develop approaches to counter the rapid increase in adiposity. One approach is bariatric surgery, the most successful clinical intervention known for treating obesity. Surgery can result in impressive weight loss and improvement of obesity-related comorbidities. Yet the mechanisms responsible for this remarkable effect of surgery remain controversial. It is now clear that caloric restriction, per se, does not explain all the reduction in stored fat mass after surgery. A number of gastrointestinal hormones, including glucagon-like peptide (GLP)-1, peptide YY, oxyntomodulin, GLP-2, glucose-dependent insulinotropic polypeptide, ghrelin, and others, can play roles in energy homeostasis and could be involved in bariatric-surgery-related weight loss and weight loss maintenance. Vagal innervation may play a role. In addition, there may be other yet-uncharacterized factors that could participate. This review discusses the possible roles of these hormonal mechanisms in various types of bariatric surgery to help elucidate some of the potential mechanisms at play in short-term and long-term post-bariatric surgery weight loss. Understanding such mechanisms could lead to new and efficacious means to control or even reduce the epidemic of obesity.

Comparative analysis of LSG versus LRYGBP bariatric surgery in management of morbid obesity and type 2 diabetes mellitus in terms of percentage weight loss and T2DM resolution

“…Other study done which also suggest weight loss & BMI reduction are as follows. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] In all diabetes pt, post-operative reduction in HbA1c (<6 normal value).In 40% patients were <6 & 35% patients were near normal range (6.1-6.5). There is good glycemic control after bariatric surgery.…”

“…Other studies which also has glycemic control are as follows. 1,2,4,6,[8][9][10]12,14,[16][17][18][19]21,22 Type of surgery in DM in 65% SG was done & in 35%. RYGB was done with similar result in glycemic control in both surgeries.…”

Hunger Hormone Profile Monitoring after Gastroplication in an Adolescent

“…Different types of surgery appear to have opposite effects on fasting and postprandial ghrelin: gastric bypass operations tend to reduce ghrelin, while restrictive ones increase or do not change ghrelin [13,15]. …”

Treating Diet-Induced Obesity: A New Role for Vagal Afferents?

“…Gastric bypass, though reasonably effective at reducing body weight, has been useful for treating type 2 diabetes [3]. The mechanism underlying these effects is not fully understood, but appears to involve decreases in consumption of high calorie foods, reductions of meal size and nutrient absorption, changes of anorexigenic and orexigenic hormone levels, increased energy expenditure, and altered vagal gastrointestinal (GI) innervation [4]. The key to the success of bypass in reducing body weight may thus be due to its effects on multiple organ systems.…”