Fatty Diet Thwarts Brain's Fullness Signal

Rats that are fed a high-fat diet appear to lose their sensitivity to a hormone that tells the body when it's had enough to eat -- and the same could be true of humans, according to researchers.

In experiments with rats fed either a high- or low-fat diet, researchers at Pennsylvania State University found that the fatty diet diminished the rodents' sensitivity to a hormone called cholecystokinin, or CCK.

CCK is secreted by the small intestine to aid in the digestion of fat and protein. It is also one of the "satiety signals" that the body produces to tell the brain that it's time to stop eating.

In the new study, rats on a low-fat diet stopped eating a fat-filled treat when the researchers gave them a dose of CCK. Not so of the animals on the high-fat diet, who ended up eating far more of the fatty snack.

The findings suggest that consistently eating high-fat foods can desensitize the body to CCK's signal to stop eating, according to Dr. Mihai Covasa, an assistant professor of nutritional sciences at the Penn State campus in University Park.

There is reason to believe that the findings in rats translate to humans, Covasa stated. He pointed to a study that found that people who followed a high-fat diet for 2 weeks gradually became less satisfied from eating fatty fare -- suggesting that, in the real world, they would have started eating more.

Covasa and colleague David M. Savastano report their findings in the August issue of the Journal of Nutrition.

Rats in the study were maintained on either a high-fat or low-fat diet for 3 weeks. When they were then tempted with a fatty snack, the animals that had lived on the high-fat diet ate more of the treat than those on the low-fat diet. And when the researchers injected the animals with CCK, they found that the hormone suppressed the low-fat group's appetite over the next hour, but not that of the high-fat group.

The findings, Covasa said, underscore the importance of minding one's fat intake, and of fitting a variety of foods and nutrients into the diet.

"You should watch how much you eat," he noted, "but the composition of what you eat is important too."

SOURCE: Journal of Nutrition, August 2005.

Reference Source 89
August 9, 2005

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