Surgery vs diet for weight loss in people with diabetes

This study compared people with type 2 diabetes (T2D) who had weight loss surgery to those who lost an equal amount of weight through diet. It found that both methods of weight loss led to improvements in blood sugar, insulin sensitivity, and metabolism.

T2D is a condition in which the body cannot control levels of glucose (sugar) in the blood. The body is less sensitive to the hormone insulin, which lowers blood glucose. T2D is related to obesity.

Weight loss (bariatric) surgery is an effective treatment for both T2D and obesity. Reducing the size of the stomach causes a feeling of fullness after eating a smaller amount of food. Fewer calories and carbohydrates lead to a smaller rise in glucose (sugar) in the blood, which improves T2D. Surgery also causes changes in metabolism. It alters the amount of GLP-1, a hormone of metabolism released by the gut after eating.  After surgery, the hormones leptin and ghrelin, which control fullness and appetite, are also altered.

It is not clear whether the improvements in T2D after bariatric surgery are due simply to weight loss, or whether surgery has additional benefits compared to diet.

This study followed 22 patients with obesity and T2D. 11 patients underwent Roux-en-Y gastric bypass surgery. The other 11 patients were in the diet group. They were given prepared foods and weekly group dietary education meetings. All of the included patients lost between 16% and 24% of their initial body weight. All participants were given tests of their metabolism before and after their weight loss. 

The diet group had significantly more improvement in their cumulative after-meal blood glucose. This was because the surgery group’s glucose rose faster and reached a higher peak level an hour after eating.

The two groups had similar improvements in free fatty acids in the blood, which are related to heart health and insulin sensitivity. Both groups also had improved beta-cell function, or the ability of the pancreas to create insulin. Both groups had changes in the gut microbiome (friendly gut bacteria which affect digestion), and these changes were greater for the surgery group.

This study showed that both bariatric surgery and substantial weight loss through diet benefit the metabolism of patients with T2D and obesity.

This trial included a small number of participants. Also, participants were not randomized to one group and this might have affected the results.

Talk to your doctor about what weight management methods are right for you.