Sleeve Gastrectomy removes part of the stomach to help with weight loss. The stomach is divided vertically from top to bottom, and the larger stomach section is then removed. This leaves a smaller gastric tube which is around 25-30% the size of your original stomach.
The Sleeve Gastrectomy encourages weight loss by reducing the amount of food you can eat and by reducing your appetite through complex hormonal mechanisms (not well understood). Your stomach will be around 70% smaller than before the surgery, meaning that the portion sizes that you are able to manage will be smaller. A Sleeve Gastrectomy is permanent and the alteration to your stomach is not reversible.
Unlike some other forms of bariatric surgery, a laparoscopic Sleeve Gastrectomy does not affect the valves or nerves in the stomach. This means that although the stomach is reduced, the stomach function largely remains intact.