A gastric sleeve is where the surgeon removes 2/3 of the stomach. This procedure also reduces appetite by removing cells that stimulate your hunger. These cells are called ghrelin and leptin. Ghrelin is responsible for driving hunger. Leptin is responsible to keeping hunger cues 'on'. When there is an abundance of fat, leptin - which is stored in the fat cells, become resistant to the hormones that try to switch it off. As a consequence, leptin is on all the time, driving hunger/appetite. This affects weight gain. Removal of these cells is effective to prevent weight regain and promote weight loss.
Figure 1: Gastric Sleeve Surgery Outline: The normal stomach (which is NOT enlarged in obese patients) holds about 1.5 litres of food. The stomach is reduced by removing the larger part of the stomach (see Figure 1). This large part of the stomach is removed completely. This leaves a small sleeve of the stomach that can only hold 150ml (1/2 cup). The stomach capacity is reduced by 70%. This means that you will not be able to eat as much as you used to. This procedure is restrictive and not malabsorptive.
Benefits of the Surgery
Negatives of the Surgery