The sleeve gastrectomy involves removing about 80% of the stomach and reshaping the remaining 20% into something that looks like a shirt sleeve. What remains of the stomach is a narrow tube or sleeve, which connects to the intestines.
While most people look at the sleeve gastrectomy as a surgery that works primarily by reducing your ability to eat large portions, its primary effectiveness is through hormonal changes. Those hormonal changes are the driving force of weight loss.
Because the stomach is removed completely, this surgery is irreversible. Many patients have downplayed the sleeve as a minor surgery, but the removal of 80% of your stomach should not be taken lightly. Even though a sleeve gastrectomy can be performed extremely safely with only a 1-2% serious complication rate, it is not a minor surgery.