Why you eat for the joy of it

Why do people keep eating when they already feel full? New research in mice suggests it may have something to do with a hunger hormone that tells you to keep chowing down.

"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," Dr Jeffrey Zigman, an assistant professor of internal medicine and psychiatry at the University of Texas Southwestern Medical Centre in the US, and co-senior author of the new study, said in a news release from the school.

Ghrelin, the hunger hormone

The researchers studied the hormones by experimenting with mice to determine whether they changed their food preferences after getting doses of the hormone, known as ghrelin.

In one experiment, mice who received ghrelin wanted to hang out in a room where they'd previously gotten high-fat food. Other mice weren't concerned about the room.

"We think the ghrelin prompted the mice to pursue the high-fat chow because they remembered how much they enjoyed it," study author Dr. Mario Perello, a postdoctoral researcher in internal medicine, said in the same news release. "It didn't matter that the room was now empty; they still associated it with something pleasurable."

How the brain handles pleasure

According to the researchers, the brains of humans and mice handle pleasure in similar ways. They next want to figure out how the brain regulates the actions of the hormone.

The study appears in the journal Biological Psychiatry. - (HealthDay News, January 2010)