Gastric bypass surgery may treat type 2 diabetes in selected patients.
Weight loss surgery has shown more effectiveness in patients with type 2 diabetes (T2D) who underwent gastric bypass surgery resulting in better insulin production in 6 months to a year without the need of further medication. This is rationalized due to dramatic weight loss and calorie cutting along after surgery. Thus, comprehending why gastric bypass is the most effective “metabolic surgery” to treat diabetes, why obese patients are noticeably less hungry post weight-loss surgery, and why improvement in diabetes after surgery may experience worsening within a matter of years are important considerations to account.
Several theories have been proposed to explain the causes of glycemic control post weight loss surgery. Some of the most common bariatric surgeries conducted are sleeve gastrectomy, Roux-en-Y gastric bypass, and gastric banding. The first two reduces the size of the stomach and the latter slows the flow of food into the GI tract. Although all three resolve T2D, gastric bypass has proven to be the most effective one. In the UK, an observational study showed that all participants who underwent gastric bypass, sleeve gastrectomy, and gastric banding were in remission at 43, 17, and 7 times higher respectively than no surgery. In comparison, gastric bypass yields more weight loss and effectiveness with nearly 2-fold higher remission rates than banding. Moreover, the National Institutes of Health-funded Longitudinal Assessment of Bariatric Surgery (LABS) study found 69% diabetes remission in obese patients in 3 years with Roux-en-Y gastric bypass versus 30% with laparoscopic gastric banding.
The compound effect of both caloric restriction and weight loss post surgery yields lower blood glucose and improves insulin sensitivity. Although results can be obtained without surgery within 10 to 20 days of caloric restriction, it is not feasible for obese patients for a prolonged period because surgery curbs appetite, increases satiety, and changes patients’ feeding behaviors. There is evidence that obese people are less sensitive to the pleasures of eating, resulting in compulsive eating. An experiment in rats on long-term food preferences post bariatric surgery showed that they no longer preferred highly concentrated sucrose, but the science behind the effects of microbiome on the brain is yet to be understood.
Reversal in satiety hormones, insulin and leptin influence eating habits as one study showed that patients were more sensitive to sweetness after surgery. A Swedish study showed reduction in remission rates from 72% to 30% after two years of bariatric surgery, versus the LABS study that showed 59% of patients ongoing remission rates after 7 years of gastric surgery indicated that non-permanent diabetes remission could reduce the risk of long-term secondary complications. Although animal studies have not shown a profound effect in reduction in “hunger hormone” ghrelin after bariatric surgery, multiple gut hormones have been associated with neuroresponse phenomena that may either affect satiety or production of insulin, followed by gastric bypass.
According to the hindgut hypothesis, the postprandial release of insulin-stimulating hormones, such as glucagon-like peptide 1 (GLP-1) is enhanced due to gastric bypass and sleeve gastrectomy. Nevertheless, study results of weight loss surgery in transgenic mice without GLP-1 receptors showed no difference in the outcome. Researchers are investigating the role of microbiome in glycemic control. Bypassing the upper or proximal small intestine may account for the procedure’s antidiabetic effects that are independent of caloric restriction, malabsorption, and weight loss. It’s theorized that prediabetic hormones are normally released when a meal passes through the proximal small intestine and that rerouting food with surgery reduces the secretion of these hormones.
In general, surgery is an ideal option for obese patients with type 2 diabetes, if lifestyle modifications and therapeutic medications have failed. Unfortunately, researchers have learned that patients with bariatric surgery are prone to depression because compulsive eating was a coping mechanism for them and a recent study found that the risk of self-harm, such as intentional drug overdose, increases, especially among patients with pre-existing mental health disorders. Moreover, former alcoholics are at an increased risk of relapsing due to either mood issues or due to calories consumed without stressing the reduced stomach. Experts emphasize on incorporating the mood-boosting physical activity following surgery to counter the unwanted adverse effects.
Currently, researchers are studying the combined effects of anti-diabetic and weight-lowering GLP-1 with other hormones. Also, a less-invasive endoscopic approach is under study by placing a tube-shaped liner and mucosal resurfacing with thermal ablation that targets the foregut. Overall, it seems likely in the near future to develop a combination of drugs that would target both obesity and T2D. Most importantly, understanding the root cause that influences the brain from eating would help in treating patients and eliminate invasive procedures.
- Weight loss surgery is not the first-line option for diabetes remission.
- Diabetes remission is evident after bariatric surgery with long-term weight loss and calorie cutting.
- Weight loss surgeries may lead to either depression, risks of self-harm or relapse in alcoholics, or decrease in diabetes remission if there is continued consumption of a high-calorie diet and being non-adherent to prescribed medications.
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American Diabetes Association. Standards of medical care in diabetes–2017. Diabetes Care. 2017; 40(Suppl. 1): S6-S10.
Greenhill C. OBESITY: Assessing the long-term outcomes of bariatric surgery in adolescents. Natures Reviews
Endocr. Macmillan, Jan 20, 2017. Web Feb 28, 2017. http://www.nature.com/nrendo/journal/v13/n3/full/nrendo.2017.2.html