Surgery is used for patients who have a BMI of 40 or higher or a BMI of 35 or higher with other risk factors. The objective of these surgical procedures is to decreases the amount of food entering or being absorbed from the gastro-intestinal tract. One of the commonest of these surgical procedures is Gastric Bypass surgery.

A form of cosmetic surgery called liposuction is performed on certain patients, to remove part of the fat deposits below the skin. In this procedure a vacuum pump is attached to a suction pipe that is thrust into the mass of fat in stomach. buttocks, thighs, etc., and the fat mass sucked out. This surgical procedure has the risk of blood loss, as a lot of blood is sucked out along with the fat.