Gastric bypass is generally the preferred method for those who have had severe diabetes for many years. In gastric bypass surgery, not only the stomach is intervened, but also the intestine to restrict nutrient absorption. Thus, the stomach is reduced and food intake is restricted. In sleeve gastrectomy surgery, the part where hunger hormones are secreted is cut off and appetite is reduced. In addition, gastric bypass surgery may cause the risk of ulcers and entanglement in the intestines, while these risks are not present in sleeve gastrectomy surgery.