There are several types of obesity surgery available to those wishing to undergo the procedure. All of which have some level of permanence, meaning that you won't be able to fully reverse the obesity surgery once you go through with it.
The most commonly known form of obesity surgery is gastric bypass, also known as stomach stapling. This procedure involves removing a large portion of the stomach from itself via a stapling device. The remains of the stomach pouch are attached to a portion of the lower intestine.
Another well known procedure is the lap band. This is a less invasive form. The doctor places a ring with an inflatable section around the upper portion of the stomach. The ring has a tube attached to it that ends with a port that the doctor can easily access to inflate the ring and gradually reduce the stomachs capacity.
Biliopancreatic Diversion, Duodenal Switch is a more involved surgery which consists of removing two thirds of the stomach and attaching the end of the stomach to a lower portion of the small intestine. The part of the intestine which was bypassed is still attached to the duodenum and its end attached to the small intestine where food is now routed to carry digestive juices to the area.
The Long Limb Gastric Bypass is similar to the above except that doctors will attach the portion of small intestine containing digestive juices further down in the intestinal tract so that the food and digestive juices have even less time to mix.
There is a form of Gastric Bypass known as the Fobi modification. A normal gastric bypass procedure is modified by the placement of a firm ring of material around the new stomach pouch.
Other types of obesity surgery are vertical banded arthroplasty (rarely used anymore), Jejuno-Ileal Bypass, and Gastric Pacing.