Appetite enhancing hormones called ghrelin are significantly reduced in severely obese patients who undergo gastric bypass surgery, according to Emory researchers. The decrease in ghrelin may explain the loss of hunger sensations and rapid weight loss in these patients.
Edward Lin, DO, assistant professor of surgery in the Emory University School of Medicine, led a study based at Emory University Hospital and Emory Crawford Long Hospital to determine if early alterations in ghrelin levels in severely obese patients undergoing weight reduction surgery may be attributed to gastric partitioning. The results of the study are published in the July 12 issue of Archives of Surgery.
The study included 42 Emory 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 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. Ghrelin levels were measured in blood plasma samples at different stages of the study, including before, during and after surgery.
"This is the first time we have found that different types of weight loss surgeries affect ghrelin levels in humans," notes Dr. Lin. "When the stomach is divided, forming a small gastric pouch, the ghrelin levels are significantly reduced early after the surgery is performed."
According to Dr. Lin, ghrelin is a hormone produced primarily in the stomach that is a powerful inducer of hunger sensation in humans and animals. It is presumed to play a role in regulating body weight and significantly increase before a meal and rapidly decline after eating, implicating this hormone as a principal signal of hunger and meal initiation. "Other mechanisms can make you hungry, but ghrelin is one of the most potent hunger stimulants."
"Patients with morbid obesity have lower baseline Ghrelin levels compared with lean counterparts," says Dr. Lin. "However, this study shows that surgically induced weight loss with RYGB in these patients appears to cause long term, if not permanent, suppression of ghrelin secretions that is not associated with other weight loss procedures."
"If you can find a way to control the release of ghrelin in the body, you can potentially prevent a person from overeating," says Lin. "This study in part explains the dramatic weight loss many people experience following gastric bypass surgery."
The reason for the observed decline in ghrelin levels is not clear. "Complete division of the stomach, forming a small vertical pouch, contributes to the decline in circulating ghrelin levels," says Dr. Lin. "but we still do not know exactly why."
Co-authors of the study are Emory faculty Nana Gletsu, PhD.; Kim Fugate; David McClusky, MD; Li H. Gu, MD; Juan-Li Zhu, MD; Bruce J. Ramshaw, MD, Dimitris A. Papanicolaou, MD; Thomas R. Ziegler, MD; and C. Daniel Smith, MD. Dr. Ziegler was supported by a grant by the National Institutes of Health, and Dr. Gletsu is supported by an Emory University Research Committee grant.