Obesity May Override Hunger Hormone


By: Jennifer Warner, WebMDNews

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