If you find yourself snacking all the time, you may want to check how much fat is in your diet.

In recent lab tests, rats on a high-fat diet snacked more than those on low-fat diets. Shots of an appetite-curbing hormone didn't change that.

Researchers working on the study included Mihai Covasa, PhD, a Pennsylvania State University assistant professor of nutritional sciences. The findings appear in The Journal of Nutrition.

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High-Fat Feast

Unlike people, the rats didn't have around-the-clock access to snacks. They couldn't raid the refrigerator in the middle of the night or nibble here and there as they pleased.

Instead, high-fat, high-calorie snacks were only available for three hours a day. It's as if a big slab of cheesecake was wheeled out in front of people, with a three-hour clock running.

Meanwhile, the rats weren't going hungry. They either got high-fat or low-fat meals. When the snacks appeared, the rats on the high-fat diet ate more than those on the low-fat diet.

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What About Weight?

The rats on the high-fat diet overindulged on fatty, high-calorie snacks. But they didn't gain more weight than the other rats.

What's their secret? It's simple. The rats just cut back at meals to make up for the snacks, instinctively budgeting for the high-fat binges.

"Rats are notorious in compensating for food to maintain a constant body weight," states Covasa in a Penn State news release. As a result, the rats all gained the same amount of weight after 20 days, he notes.

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Hormone's Effects

The test got a twist when the researchers gave the rats shots of a hormone called CCK (cholecystokinin).

CCK is one of several hormones tied to appetite. It triggers feelings of fullness, effectively telling the body, "Got enough food now; stop eating."

The CCK shots curbed snacking in the rats on the low-fat diet. But the shots had less impact on rats on the high-fat diet.

The rats on the high-fat diet apparently were less sensitive to feeling full, which boosted snacking more and cut sensitivity to CCK, write the researchers.

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Keep in Mind

The study didn't involve people. No human study of snacking and CCK has been reported, states the news release.

In addition, fat is an important part of the diet, but the type and amount of fat matters.

Also, the rats were free to eat high-fat snacks every day -- not as an occasional treat.

Lastly, CCK isn't the only thing that makes us put the fork down or seal up the bag of potato chips. But the hormone is "one important feedback signal" that would normally limit eating, write the researchers.

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By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Savastano, D. The Journal of Nutrition, August 2005; vol 135: pp. 1953-1959. News release, Pennsylvania State University.