Researchers now say they might have a partial explanation for the loss of hunger and rapid weight loss observed after gastric bypass surgery. In the gastric bypass procedure, the stomach is divided to create a pouch out of the small proximal portion of the stomach, which is then attached to the small intestine, bypassing a large part of the stomach and all of the duodenum.
It was found that in severely obese patients who have the surgery show significant early declines in levels of a hormone that stimulates appetite. The hormone ghrelin is an appetite stimulant produced primarily in the stomach. It plays a role in regulating body weight. In most people, ghrelin levels significantly increase before a meal and rapidly decline after eating. This implies ghrelin is a principal signal of hunger and meal initiation.
Researchers say they found ghrelin levels were not significantly changed in severely obese patients who had other gastric procedures that did not involve complete division of the stomach or who had anti-reflux surgery. Among patients who had gastric bypass, average ghrelin levels before surgery were 355 picograms per milliliter compared to post-operative levels of 246 picograms per milliliter.
Thus researchers conclude saying that weight reduction procedures that do not sufficiently exclude gastric fundus tissue may not adequately lower ghrelin levels, reduce hunger, and, thus, induce optimal weight loss.