Gastric Bypass, also called Roux-En-Y gastric bypass, is a type of Obesity / Weight-Loss surgery that involves creating a small pocket from the stomach and connecting it directly to the small intestine, creating a detour.
It will be separated from the small part with a clip, but not removed. The intestine will look like a Y-shape. After gastric bypass, swallowed food will go into this small pocket of stomach and then directly into the small intestine. This way, it is detouring most of your stomach.
With Bypass Surgery, when food is consumed, food bypasses (goes around) the upper part of the small intestine. These steps of the surgery lead to neurohormonal changes which reduce hunger, increase feelings of fullness and help with weight loss.