Why is the small intestine shortened?

Shortening the small intestine is the malabsorptive element to gastric bypass surgery as the shorter intestine prevents excess food being absorbed by the body.

The small intestine is divided, creating a Y shape. The lower part of the small intestine (the jejunum) is connected to the smaller stomach, providing a channel for food to leave the stomach and be digested. The two sections of the Y-shaped small intestine are joined to allow the unused portion of the stomach to drain fluids.

The Y shape shortens the intestine, meaning food has a shorter journey to reach the large intestine. It is during the journey of food from the stomach to the large intestine that the body absorbs calories. By bypassing the upper section of the small intestine (the duodenum), less food is absorbed by the body.