Roux-en-Y Gastric bypass surgery is an operation in which a small pouch of stomach is created and joined to the small intestine after bypassing an initial segment of small intestine known as duodenum and jejunum. By this arrangement there is delay in mixing of ingested food, and the digestive enzymes.
The net effect of this re-arrangement is a restricted intake of food; and due to the bypass, some malabsorption also takes place, leading to weight loss and resolution of Diabetes. However it is not only the restriction and malabsorption that leads to weight loss and correction of co-morbidities in obese people. The intestine in our body secretes a number of hormones, which are increased when exposed to undigested food. These hormones modify the metabolism in our body in such a way that diabetes is either resolved or controlled. Similarly blood pressure and a host of other problems are corrected due to these hormonal changes. Some of these hormones also increase our resting metabolic rate such that we consume more energy even at rest.