Bariatric surgery is a procedure that makes changes to the digestive system in order to help people with severe or morbid obesity to lose weight.
Research has shown that, depending on which form of surgery they have, many individuals who undergo bariatric or weight loss surgery manage to lose around 15% to 30% of the weight they were prior to surgery. However, none of the procedures can guarantee weight loss and some individuals are disappointed with the results. Factors that may influence how much weight is lost post-operatively include how obese the person was in the first place and the surgical method applied.
The main procedures in bariatric surgery include Roux-en-Y gastric bypass, gastric band and sleeve gastrectomy. Currently, research is ongoing into the safety, effectiveness, and long-term outcomes of the different procedures, as well as the possibility of alternative, non-surgical treatment options.
A study by K Ryan and R Seeley (University of Cincinnati, Ohio, US) investigated how vertical sleeve gastrectomy (VSG) leads to health benefits for obese individuals. VSG involves a reduction in stomach size of around 80% and the creation of a gastric “sleeve” to connect the small intestine to the esophagus. The procedure is known to increase the amount of circulating bile acids, which bind to a receptor that regulates the expression of a gene called farsenoid-X receptor (FXR). To investigate whether the influence VSG has on weight loss is associated with FXR, the team compared knock-out mice that did not have the FXR receptor to mice that did have the receptor.
As reported in Nature in 2014, all of the mice were fed a high-fat diet until they became obese and then subjected to VSG. Following the procedure, all mice lost weight and their glucose tolerance improved. The composition of their gut microbes also changed. However, among the mice that did not have the FXR receptor, the improved glucose tolerance and weight loss were significantly less than that among the FXR mice.