June 28, 2004 -- Obesity may interfere with a natural hunger ho
June 28, 2004 -- Obesity may interfere with a natural hunger hormone and override the body's natural ability to regulate appetite and weight, a new study shows.
Researchers found obesity suppressed the natural spike in the hunger hormone that occurs at night. Findings also showed that obese people have a blunted hormone response associated with meals.
If more studies confirm these findings, researchers say this may open up new avenues for developing treatments for obesity that help people restore their natural weight control mechanisms.
The hormone ghrelin is released by the stomach, and is part of a complex system that regulates how much people eat and how many calories they burn off. In obesity this system may be abnormal. Blood levels of ghrelin are known to increase prior to meals and decrease after food intake in normal healthy people.
"It's possible that obese people have developed biological mechanisms that make them resistant to their own hormones," says Julio Licinio, MD, professor of psychiatry and medicine at the University of California, Los Angeles, in a news release. "We must try to solve this mystery and explore new drugs to make them more sensitive to their bodies' internal cues."
Obesity Disrupts Hunger Hormone
In the study, published in today's online edition of the Proceedings of the National Academy of Sciences, researchers compared ghrelin and other hormone levels during the course of a day in five obese and five lean males.
Levels of the hormone usually show specific daily patterns, spiking just before meals and dropping after eating. But researchers found the pattern of ghrelin levels differed significantly between the obese and lean men.
Ghrelin levels spiked among the lean men at night, between midnight and 6 a.m. These surges surpassed spikes found before meals. But the levels of the hormone throughout the 24-hour period remained relatively flat among the obese men. The researchers found that the hormone response before and after meals was blunted in the obese men.
"The most powerful ghrelin surge was missing in the obese men, suggesting that their regulatory system has gone awry or can no longer able to listen to its own cues," says Licinio.
"This defies the stereotype of overweight people waking up in the middle of the night to raid the refrigerator," says Licinio. "The men in our study slept through the night, and both groups ate meals designed to maintain their current weight."
Researchers say the blunting of the nighttime ghrelin surge may be a biological feature of obesity that merits further research in order to develop better treatments to target obesity.
SOURCE: Yildiz, B. Proceedings of the National Academy of Sciences, online early edition, June 28, 2004.
