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Exercise: The Antidote for a High-Fat Meal

Even a mild workout reverses arterial damage, study suggests

THURSDAY, Aug. 31, 2006 (HealthDay News) -- So, you've just polished off a meal high in fat, and now you're feeling guilty? Wait an hour or two, then get a little exercise, and you can reverse the potential damage to your arteries, a new study suggests.

And you don't even have to head to the gym for that exercise. "We're talking about a walk, we're not talking about changing your clothes and sweating," said Janet P. Wallace, a professor of kinesiology at Indiana University, and lead investigator for the study.

The study, coincidentally, follows another study published earlier this month in the Journal of the American College of Cardiology in which researchers found that eating just one piece of carrot cake high in saturated fat and drinking a milkshake can reduce the body's ability to protect itself against heart disease.

The fat in the cake and shake, it seems, reduces the ability of the body's "good" cholesterol -- the high-density lipoprotein, or HDL -- to do its job --protecting the inner lining of the arteries from inflammatory substances that promote vessel-clogging plaque.

According to Wallace, after a fatty meal, arteries lose their ability to expand in response to an increase in blood flow. The effect peaks four to six hours after eating -- usually just in time for your next meal. So, four hours after a fatty meal, your arteries look like those of a person with heart disease, she said.

"That post-meal period is a hot topic among all the researchers in heart disease, diabetes and obesity," Wallace said. "That period sets up the environment for the artery to be unhealthy. And when the artery is unhealthy, that is when it leads to heart disease, insulin resistance and other problems."

To see if exercise could make a difference, Wallace and her colleagues studied eight healthy 25-year-olds, looking at three scenarios. Each of the participants -- five men and three women -- completed all three scenarios. They ate a low-fat breakfast. They ate a high-fat breakfast. And they ate a high-fat breakfast followed two hours later by a 45-minute walk on a treadmill at a moderate pace. The high-fat meal contained about 48 grams of fat and the low-fat one actually had no fat; each consisted of about 940 calories.

The researchers used a blood pressure cuff to measure blood flow in the brachial artery, located in the arm, before and after each scenario. "The brachial artery represents what is going on in the arteries of the heart," Wallace said.

After the high-fat meal alone, the brachial artery dilation dropped from 6 percent to 4 percent, Wallace said. "The ideal range is about 6 to 10," she said. "A range of 3 to 5 is not good."

After the low-fat meal, dilation went from 6 percent to 6.5 percent, a slight improvement.

But, "after the high-fat meal and exercise, it went from 6 percent (before the meal) to 8 and a half percent," she said.

"Exercise does great things, and this obviously shows exercise is very effective in counteracting that high-fat meal," Wallace added.

The study results were published in the September issue of the European Journal of Applied Physiology.

Next, Wallace hopes to study the effect of exercise before a high-fat meal. "I think we will find it works as well." She emphasized that her research isn't meant to encourage people to indulge in high-fat fare. But she's realistic: "There are people who are going to eat high-fat meals," she said.

If you're a fatty-food fan, Wallace suggests some exercise -- after getting your doctor's OK.

But Jeannie Moloo, a Sacramento, Calif., registered dietitian and a spokeswoman for the American Dietetic Association, offered a caveat about the study: "We need to keep in mind the results apply only to the population investigated and that was young, healthy and physically active adults. The small number of subjects, only eight, makes it difficult to tell if there are differences in responses between men and women."

And Moloo, like Wallace, cautioned that the research isn't an excuse to indulge in fatty foods.

More information

To learn more about a healthy diet, visit the American Dietetic Association.

SOURCES: Janet P. Wallace, Ph.D., professor, kinesiology, Indiana University, Bloomington; Jeannie Moloo, R.D., Ph.D., spokeswoman, American Dietetic Association, and registered dietitian, Sacramento, Calif.; September 2006 European Journal of Applied Physiology
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