July 12, 2004 -- A sudden drop in a hormone that stimulates appetite may be at least partially responsible for the rapid weight loss seen in obese persons who undergo gastric bypass surgery, a new study suggests.
Researchers found that levels of the hunger hormone known as ghrelin declined significantly following gastric bypass surgery. Gastric bypass is a common form of weight loss surgery in which the stomach is made smaller by creating a small pouch. The pouch is attached to the middle portion of the small intestine, bypassing the rest of the stomach and the upper portion of the intestine.
Ghrelin is a hormone produced in the stomach that triggers appetite and is thought to play an important role in regulating body weight. Levels of ghrelin typically rise before meals and quickly decline after eating.
"This study demonstrates that complete division of the stomach, forming a small vertical pouch, contributes to the decline in circulating ghrelin levels," write researcher Edward Lin, DO, of the Emory University School of Medicine, and colleagues. "This may explain, in part, the loss of hunger sensation and rapid weight loss observed following gastric bypass surgery."
Weight Loss Surgery Stalls Hunger Signals
In the study, published in the July issue of the Archives of Surgery, researchers measured ghrelin levels in 42 morbidly obese persons before and after surgery. Thirty-four of the participants underwent a gastric bypass and eight had other forms of procedures involving the stomach. Six non-obese persons undergoing anti-reflux surgery also served as a comparison group.
The study showed that levels of ghrelin were much lower in obese persons following gastric bypass surgery. Before surgery, ghrelin levels were 355 picograms per milliliter among those who had a gastric bypass compared with 246 picograms per milliliter following the procedure.
No significant changes were found in ghrelin levels among obese persons who had other gastric procedures or in the non-obese comparison group.
Researchers say they believe this is the first study in humans to show a decline in ghrelin following gastric bypass surgery.
They say the results suggest that weight loss surgeries that do not involve reducing or dividing the stomach tissue may not adequately lower ghrelin levels, reduce hunger, and induce weight loss.