Gastric bypass is a method of treating obesity. During the operation, the volume of the stomach is reduced by separating the upper part of the stomach from the rest of the stomach, and the digestive tracts is shortened by connecting the reduced stomach directly to the middle part of the small intestine. This limits the amount of food a person eats and reduces the amount of calories and nutrients one absorbs as food bypasses part of the digestive system. Surgery-induced changes in hormones that help a person feel full for longer lead to the suppression of appetite and restoration of the metabolic syndrome caused by obesity.
Gastric bypass surgery is applied when other methods of treating obesity, such as diet and physical activity, are not effective, or when being overweight causes serious health problems.
This surgery can be performed on patients with a body mass index (BMI) of 40 or more, or with a body mass index between 35 and 39.9. In rare cases BMI may be lower, but patients have overweight-related health problems, such as heart disease, high blood pressure, high cholesterol, type 2 diabetes, etc.