Ghrelin: The Hunger Hormone

Your stomach produces a hormone called ghrelin, which stimulates your appetite and encourages you to eat. That's a good thing for some people, not so good for others. Here's what researchers know about this mysterious chemical messenger that appears to have such a profound and direct effect on one's ability to lose weight.

Ghrelin was discovered in 1999 by Japanese researchers studying laboratory rats, and the following year, its role in hunger was confirmed by American scientists. They found that blood levels of ghrelin increase when you don't eat and decrease when you do. Since that time, numerous studies have shown that thin people have higher levels of ghrelin than obese people, which has helped researchers to understand that body weight affects ghrelin's ability to regulate hunger cues and appetite.

Some people, such as those who suffer from a rare condition known as Prader-Willi Syndrome, never seem to be able to satisfy their appetites and as result, suffer from and often die from complications of obesity. When scientists found that ghrelin levels in people with this condition are abnormally high, research to try to find a ghrelin blocker began. Scientists theorized that if a ghrelin blocker could be developed to help people with Prader-Willi Syndrome, maybe it could help others control weight as well.

When Dr. Roy G. Smith and his colleagues at the Huffington Center on Aging at Baylor College of Medicine studied ghrelin-blocking substances in human subjects, they found that people do not lose weight when their ghrelin levels are low, but they do build more muscle mass. Since people with more muscle burn more calories and clear glucose from their blood more efficiently, this type of research could contribute to the development of drugs that can help prevent obesity and complications from diabetes.

Yale University researchers also found that ghrelin exists in the hypothalamus, which is the part of the brain that works with the stomach to regulate appetite. As it turns out, ghrelin is not only associated with weight and growth, but also with stress-induced depression and anxiety, which in turn is linked to weight gain in many people. This information lead researchers to question if and how ghrelin in the brain works with ghrelin in the stomach to regulate hunger and food intake.

Most of the research being performed on ghrelin and ghrelin blockers is still being performed on laboratory animals and while the promise of a ghrelin blocker is on the horizon, there are still many questions to be answered. As they fit the puzzle pieces together and unravel the secret of this hormone's appetite regulating power, the next challenge for obesity researchers is to take the information they have collected from lab rats and develop a medication or vaccine that will truly help fight fat in humans.


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Sorelle, R. "Fighting Obesity One Molecule at a Time."  Baylor College of Medicine's Solutions. Fall 2006; 2(3). 10 Oct 2008. Web. 22 July 2010.

Olszewski, P., Schioth, H., and Levine, A. "Ghrelin in the CNS: From Hunger to A Rewarding and Memorable Meal? Brain Research Reviews. 2008 June; 58(1): 160-170. 2008 Feb 13. Web. 22 July 2010

Southwestern Medical Center. "Hunger Hormone Increases During Stress, May Have Antidepressant Effect, Researchers Report. June 15 2008. Web. 22 July 2010

Yale University. "Yale Researchers Find New Target in the Brain to Regulate Appetite and Food."  20 Feb 2003 Web. 22 July 2010