In gastric bypass surgery, a large part of the stomach is bypassed, a small volume stomach section is prepared and connected to the lower part of the small intestines, which are divided into two. In this surgery, a restrictive surgery is performed by reducing the stomach volume and disabling a part of the intestines, as well as aiming to eliminate some of the consumed food without being absorbed, and malabsorption develops.

Thus, patients are satisfied with less food and only a certain part of the food they consume is absorbed. However, there is a significant improvement in gastrointestinal system hormones and their metabolic effects, especially incretin hormones that are disrupted in diabetes. Although the role of ghrelin in Roux en Y Gastric Bypass (RYGB) is not clear, the role of obestatin has begun to be emphasized in recent studies. Obestatin may be a potential mediator to improve glucose homeostasis after RYGB. Increased obestatin secretion may be an important mechanism by which RYGB improves obesity and type 2 diabetes mellitus.