A band is placed at the upper end of the stomach to divide the stomach into a small upper part and a large lower part, slowing the passage of food.

Part of the stomach is removed, the small intestine is divided, and the upper part is connected to the lower part, bypassing much of the middle part of the small intestine. 

Part of the stomach is removed, making the stomach into a narrow tube. The small intestine is not altered.

Part of the stomach is detached from the rest, creating a small pouch. The pouch is connected to a lower part of the small intestine.