Severely obese patients who undergo gastric bypass surgery show significant early declines in levels of a hormone that stimulates the appetite. This may possibly explain, in part, the loss of hunger sensation and rapid weight loss observed following gastric bypass, according to a new study.
From JAMA:
Appetite-stimulating hormone levels decrease after gastric bypass surgery
Severely obese patients who undergo gastric bypass surgery show significant early declines in levels of a hormone that stimulates the appetite. This may possibly explain, in part, the loss of hunger sensation and rapid weight loss observed following gastric bypass, according to an article in the July issue of The Archives of Surgery, one of the JAMA/Archives journals.
According to information in the article, the hormone ghrelin is a circulating appetite stimulant produced primarily in the stomach. It plays a presumed role in regulating body weight. Circulating ghrelin levels significantly increase before a meal and rapidly decline after eating, implicating this hormone as a principal signal of hunger and meal initiation.
Edward Lin, D.O., and colleagues at Emory University, Atlanta, conducted a study to determine if early alternations in ghrelin levels in severely obese patients undergoing weight reduction surgery may be attributed to gastric partitioning. The study included 42 patients who were morbidly obese, with a body mass index (BMI) of 40 or higher, and six lean control patients. (BMI is calculated as weight in kilograms divided by the square of height in meters.)
Thirty-four patients underwent Roux-en-Y gastric bypass (RYGB), a procedure in which the stomach is divided to create a pouch out of the smaller proximal (near) portion of the stomach, and then attached to the small intestine, bypassing a large part of the stomach and all of the duodenum. Eight patients underwent other gastric procedures that did not involve complete division of the stomach. Six non-obese patients undergoing anti-reflux surgery served as lean controls. The researchers measured ghrelin levels in blood plasma samples at different stages of surgical intervention.
”A divided gastroplasty creating a small proximal gastric pouch results in significant early declines in circulating ghrelin levels that are not observed with other gastric procedures,” they report.
Among the patients undergoing gastric bypass, preoperative mean levels of ghrelin were 355 picograms per milliliter (plus or minus 20), compared with postoperative levels of 246 picograms per milliliter (plus or minus 13). Ghrelin levels were not significantly changed in severely obese patients undergoing other gastric procedures, or in lean controls. Compared with the morbidly obese subjects, the lean controls had significantly higher plasma ghrelin levels at baseline.
”This study demonstrates that complete division of the stomach, forming a small vertical pouch, contributes to the decline in circulating ghrelin levels,” the authors write. ”It further supports that the decline in ghrelin levels following RYGB surgery is not a gradual process, but occurs early following the procedure.”
The authors believe this is the first human study to demonstrate a reduction in circulating ghrelin early following division of the stomach during RYGB surgery.
”We show that division of the stomach and exclusion of the gastric fundus play an important role in reducing circulating ghrelin levels from baseline levels. If ghrelin remains a principal stimulant of food intake in morbid obesity, the results of this study would suggest that weight reduction procedures that do not sufficiently exclude gastric fundus tissue may not adequately lower ghrelin levels, reduce hunger, and induce optimal weight loss,” they conclude.