Fitness Impacts Heart Disease Risk

Low Fitness Levels Linked to Other Heart Disease Risks Even In People Without Heart Disease

From the WebMD Archives

Dec. 20, 2005 -- One in five American teens and adults don't handle exercise well -- especially women and minorities. It's setting them up for heart disease, obesity, diabetes, and other chronic health problems.

It's "the first sign of a burgeoning obesity epidemic ... a prevalent and important public health problem in the U.S.," writes researcher Mercedes R. Carnethon, PhD, a researcher with the Feinberg School of Medicine at Northwestern University in Chicago.

"Although teens are not generally considered at risk for having heart attacks in the short term, developing risk factors in their early adulthood sets the stage for heart disease in middle age and older," she writes in this week's edition of The Journal of the American Medical Association.

Risks of Physical Inactivity

Researchers have long been known that physical inactivity is a risk factor for heart disease - along with other risks such as high LDL "bad" cholesterol and blood pressure levels. However, it's not been clear just how widespread the inactivity problem is, says Carnethon. Adding more fuel to this issue, a recent international study showed that 12% of heart attacks are due to inactivity, she notes.

Her study involved a random national sample of more than 3,000 teens (12-to-19 years old) and 2,205 adults (20-to-49 years old) who did not have symptoms of heart disease. They all had an exercise treadmill test, also known as a stress test, to see how their hearts functioned when exercising. The treadmill test indicates how well their hearts handle work (exercise). It measures heart rate, breathing, and blood pressure, and monitors the heart. The test is used to measure heart disease but can be used to measure overall fitness level.

After their exercise treadmill tests, 34% of teens -- and 14% of adults -- were in the "low fitness" category, reports Carnethon.

Among teens, low fitness level did not differ between boys or girls. In adults, however, females were significantly more likely to have low fitness levels. Also, blacks and Mexican-Americans were less fit than whites.

Other heart disease risk was also linked to low fitness levels. For example, for measures of excess weight (body mass index), adults and teens with low fitness levels were two to four times more likely to be overweight or obese, compared with those of moderate-to-high fitness. The inactive adults and teens also had higher total cholesterol and blood pressure levels.


Low fitness levels lead to high blood pressure, high cholesterol levels, and diabetes, as well as the metabolic syndrome -- a cluster of heart disease and diabetes risks, she notes.

Her study did not include older adults, who are at greatest risk of heart disease. Therefore, it likely is a low estimate of the overall public health problem, she says.

The trend is reversible, Carnethon writes. Studies have shown that when individuals improve their fitness levels, they have fewer of these risk factors. She calls for better programs to educate teens and adults about the importance of exercise.

WebMD Health News Reviewed by Brunilda Nazario, MD on December 20, 2005


SOURCES: Carnethon, M. The Journal of the American Medical Association, Dec. 21, 2005; vol 294: pp 2981-2988. WebMD Medical Library with Healthwise: "Exercise Electrocardiogram."

© 2005 WebMD, Inc. All rights reserved.


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