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Exercise Shown to Have Positive Effect On Cholesterol

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Duke Health News 919-660-1306

DURHAM, N.C. -- For the first time, Duke University Medical
Center researchers have demonstrated that exercise -- without
accompanying weight loss -- has a positive impact on improving
cholesterol levels.

Furthermore, they report that it is the amount of activity,
and not necessarily any changes in fitness or intensity of
exercise, that is important for cholesterol improvement. In the
process of their studies, the Duke researchers also
demonstrated that the standard lipid panels used by doctors to
measure the so-called "bad" LDL and "good" HDL forms of
cholesterol do not necessarily provide the most accurate
information in determining one?s risk of developing heart
disease.

The results of the Duke study, published today (Nov. 7,
2002) in the New England Journal of Medicine, show that
exercise has a positive effect on the number and size of the
particles that carry cholesterol through the bloodstream.

Cholesterol is an energy-rich fat, or lipid, that must
"attach" to protein particles in order to circulate throughout
the bloodstream and nourish tissues. This combined
cholesterol-protein unit is known as a lipoprotein, and
abnormal levels of these lipoproteins have been linked to the
progression of atherosclerosis and heart disease.

"It appears from our study that cholesterol carried by
smaller, denser protein particles appear to cause
cardiovascular disease more efficiently than cholesterol
carried by large, fluffy particles," said Duke cardiologist
William Kraus, M.D., who led the study.

"We showed that increasing amounts of exercise increased the
size of the particles carrying both the good and the bad
cholesterol," Kraus continued. "By using new methods of
measuring the particles carrying cholesterol, we found that
some exercise is better than no exercise, and conversely, those
patients in the control group who did not exercise actually
showed worsening cholesterol levels."

According to Kraus, past studies of exercise?s effects on
cholesterol have been unable to find a link because the
measurements were based on the standard lipid levels as opposed
to the actual cholesterol-carrying particles.

"This study had to be done because there was very little
scientific information indicating whether or not exercise
training would have beneficial effects on cholesterol when
conducted in a state-of-the art, randomized fashion, comparing
individuals who exercised to those who did not," Kraus
said.

For example, exercise guidelines issued recently by the
Centers for Disease Control and Prevention and the National
Academy of Science are based more on expert opinion and
consensus than data gained from controlled clinical studies,
Kraus said.

The study, which is still studying patients, was funded by a
$4.3 million grant from the National Heart, Lung and Blood
Institute. One-third of the patients in the study were enrolled
at East Carolina University (ECU), with the rest enrolled at
Duke. Joseph Houmard, Ph.D., led the ECU portion of the
study.

The results are based on the analysis of blood cholesterol
changes in 84 sedentary overweight men and women with elevated
lipid levels who were randomized to one of three different
exercise groups: high-amount/vigorous intensity (the caloric
equivalent of 20 miles of jogging per week);
low-amount/vigorous intensity (equivalent of jogging 12 miles
per week); and low-amount/moderate intensity (equivalent of
walking briskly for 12 miles per week). Importantly, Kraus
said, the group included significant numbers of
African-Americans, as well as equal numbers of men and
women.

"While several studies have shown that low intensity
exercise can improve lipoproteins, the data from this study,
taken together with other research, suggests that if there is
an exercise intensity effects on lipids, it is small compared
to the much clearer role that the amount of exercise plays,"
Kraus said.

In order to determine the role of exercise alone,
participants were not allowed to change their diet during the
course of the study. Each participant followed a two- to
three-month "ramp-up" exercise period, followed by six months
of exercise, which was carried out on cycle ergometers,
treadmills or elliptical trainers in a supervised setting.

Throughout the course of the study, researchers took blood
samples from participants, and then used two new and different
methods to determine the subtle and specific changes in
cholesterol particle size and number.

While Kraus, an ardent proponent of the benefits of
exercise, believed that it would have a beneficial effect on
cholesterol, he was most surprised by what appeared to happen
to the control group that did not exercise during the course of
the study.

"We were actually surprised that the individuals who did not
exercise deteriorated as rapidly as they did in measurements of
blood cholesterol, weight gain and overall health," he said.
"This is characteristic of what is happening to the American
population. So if we can get these people exercising, perhaps
we can prevent bad things from happening."

Kraus believes that during the next 10 years, physicians
will gradually move away from using the standard lipid profile
tests and begin to look more closely at particle size to
determine their patients' risk for heart disease. According to
Kraus, inactivity ranks closely behind smoking as the greatest
risk factor for heart disease, and like smoking cessation,
exercise is a lifestyle modification proven to protect the
heart.

"Exercise can be a very powerful way of reducing risk, not
only by improving lipids as our study has shown, but also by
having a positive effect on glucose levels and mood
modification," he said. "We should understand that patients do
not need to lose weight or focus so much on the scale, but they
do need to exercise to decrease their risk of heart
disease."

Joining Kraus in the study were, from Duke, Cris Slentz,
Ph.D., Brian Duscha, Kenneth Knetzger, Connie Bales, Ph.D.,
Sarah Henes and Gregory Samsa, Ph.D. From ECU, other team
members were Michelle Wharton and Jennifer McCartney.

James Otvos, Ph.D., from LipoScience, Inc., Cary, N.C., and
Krishnaji Kulkarni, Ph.D., from Atherotech, Inc., Birmingham,
Ala., were also members of the team. LipoScience and Atherotech
developed the two different technologies for analyzing the
blood samples. Kraus has no financial interest in either
company.

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