Physical fitness can reduce your rate of death from heart disease, regardless of whether you're already at high or low risk of heart disease, according to a study published yesterday in the journal Circulation.

"It's a wake-up call, another one," says co-author Peter Katzmarzyk, a physical activity epidemiologist at Queen's College in Kingston, Ontario. "We've shown that physical fitness is a powerful predictor of mortality."

Katzmarzyk and his colleagues at The Cooper Institute in Dallas studied more than 19,000 men who came in for an exam from 1979 to 1995. They measured their physical fitness by putting the men on a treadmill, slowly increasing both speed and elevation, and measuring exertion. Then, they followed up about 10 years later and looked at which of the men had died of cardiovascular disease. Even those men who had been put into the high-risk category based on other risk factors—such as family history of heart disease or smoking—were less likely to die when they were in good shape than their peers who had similar risks but were not physically fit.

Men in the highest-risk group were twice as likely to die of heart disease when they were not physically fit. In the low-risk group, men who weren't physically fit were five times more likely to die than others with low heart disease risk and good physical fitness.

Because heart disease is so prevalent—it's currently the leading cause of death in the United States—Katzmarzyk says that all people should make an effort to become physically active.

"Physical activity is one of the most important things we can do for our health," he says. "But our entire society is set up to be sedentary. We've engineered physical activity out of our life." People should take the time to walk to work, to the grocery store, or up the stairs to their office, he says. It could help save their lives.

Find out more: Go to the U.S. News guide on coronary heart disease to get in-depth information about symptoms, tests, treatment, and prevention.