Researchers find clues to why some continue to eat when full

08:52, December 29, 2009      

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The so-called hunger hormone ghrelin might work in the brain to make some people keep eating "pleasurable" foods when they're already full, according to a new research.

For the study, researchers at University of Texas Southwestern Medical Center conducted two standard behavioral tests.

In the first, they evaluated whether mice that were fully sated preferred a room where they had previously found high-fat food over one that had only offered regular bland chow. They found that when mice in this situation were administered ghrelin, they strongly preferred the room that had been paired with the high-fat diet. Mice without ghrelin showed no preference.

For the second test, the team observed how long mice would continue to poke their noses into a hole in order to receive a pellet of high-fat food. The animals that didn't receive ghrelin gave up much sooner than the ones that did receive ghrelin.

Humans and mice share the same type of brain-cell connections and hormones, as well as similar architectures in the so-called "pleasure centers" of the brain, said the study.

In addition, the behavior of the mice in this study is consistent with pleasure- or reward-seeking behavior seen in other animal studies of addiction, said Dr. Jeffrey Zigman, assistant professor of internal medicine and psychiatry at the center.

"What we show is that there may be situations where we are driven to seek out and eat very rewarding foods, even if we're full, for no other reason than our brain tells us to," Zigman said.

Rewards, he said, generally can be defined as things that make people feel better.

"They give us sensory pleasure, and they motivate us to work to obtain them," he said. "They also help us reorganize our memory so that we remember how to get them."

Dr. Mario Perello, postdoctoral researcher in internal medicine and lead author of the study, said the idea was to determine "why someone who is stuffed from lunch still eats -- and wants to eat --that high-calorie dessert."

"We think the ghrelin prompted the mice to pursue the high-fat chow because they remembered how much they enjoyed it," Dr. Perello said. "It didn't matter that the room was now empty; they still associated it with something pleasurable."

The study was appearing in the online edition of Biological Psychiatry on Monday.

Source: Xinhua
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