Gastric bypass works in two ways: restriction and malabsorption.
Restriction of large amounts of food
The stomach is stapled to create a small gastric pouch that is connected to the rest of the small intestine. This reduces the actual size of the ‘functional’ stomach from about 400 ml to approximately 30 ml and limits the amount of food consumed at one time, therefore restricting food intake.
Malabsorption of nutrients
Bypassing the stomach and between 75 and 100 centimeters of the small intestines results in the malabsorption of fats and carbohydrates, which further adds to the efficacy of the procedure. The combination of malabsorption and restriction make gastric bypass an effective procedure for surgical weight-loss.
Gastric bypass also results in an effective resolution of major illnesses that ordinarily accompany obesity. Nearly 85 to 90 percent of overweight patients suffering from hypertension, diabetes, sleep apnea and other major illnesses will see a significant improvement or resolution after undergoing gastric bypass.