The primary means by which the Gastric Bypass operation works is by restricting the amount of food that can be eaten at a single meal. The small gastric pouch varies somewhere between 15 and 30 ccs in size. This amounts to only a few ounces of solid food at a time. Eating too much volume will produce discomfort and eventually vomiting, both of which reinforce eating small amounts of food slowly.

In addition, because the first part of the small intestine (duodenum) is bypassed, along with the distal stomach, the digestive juice does not reach the food until the connection at the “Y”. This has particular importance for sugar intake, because sugars require enzymes from the pancreas to be broken down for absorption. A high concentration of sugars in the small intestine which are not absorbed lead to the Dumping Syndrome. This is a combination of flushing, cramping and diarrhea, often as a severe brief episode. Sugar intake, particularly processed sugars, must be restricted after Gastric Bypass or the patient will suffer from the Dumping Syndrome.

Finally, since no food will pass through the distal stomach and proximal intestine there is very little stimulation for the production of most intestinal hormones. Intestinal Hormones are chemicals produced by the intestinal tract that are excreted into the blood stream and cause effects remote from the intestine (e.g. insulin). Some of the hormones have an effect on how the brain perceives hunger. For example, Ghrelin, an intestinal hormone thought to drive hunger, stays at a very low level after Gastric Bypass. As a result, most patients do not suffer wide swings in hunger shortly after eating, and the drive to eat is generally diminished.

Because of a combination of the above factors the Gastric Bypass operation has demonstrated excellent weight loss for almost all patients. Its reliability has made the Gastric Bypass the Gold Standard weight loss surgery in the United States.