The answer lies in the digestive system's small intestine, French scientists report in Cell Metabolism.
Protein cuts hunger, leading people and animals to eat less, they write. But how?
That's what the French study is all about. It only involved rats, but it could explain how protein takes the edge off your hunger.
The researchers included Gilles Mithieux of INSERM, France's national institute of health and medical research and France's Universite Claude Bernard Lyon 1.
Extra Helping of Protein
Some of the rats were fed a starch-enriched diet. Others ate food that was moderately enriched with extra protein.
The rats weren't fussy eaters. They didn't favor either type of chow. Whatever was dished up, they ate.
After digesting their food, the rats in the high-protein group made glucose (blood sugar) in their small intestines, the researchers report.
The small intestine is part of the digestive system. Food goes there first after leaving the stomach to be further broken down for the body's use.
The glucose that Mithieux and colleagues are talking about wasn't released from food. It was made by specialized cells in the small intestine, according to the researchers.
That glucose then entered the bloodstream, sending an "I'm full" message that eventually reached the brain.
The brain, in turn, basically said, "No need for any more food right now. Back away from the chow. Go scamper around the cage for a while, or do something else. Just quit eating for now."
The rats obeyed. But people are a little different. We've been known to linger at the plate when we're not really hungry.
It's not known if the small intestine in people makes glucose after a protein-rich meal. But it's worth finding out, write the researchers.
They suggest that if people handle protein like rats do, it could lead to new approaches to food intake disorders, in which the body's hunger and fullness signals are overridden.
SOURCES: Mithieux, G. Cell Metabolism, November 2005; vol 2: pp 321-329. News release, Cell Press.
By Miranda Hitti
Reviewed by Louise Chang, MD
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