A
preliminary study by Duke University Medical Center researchers
indicates that moderate exercise alone can improve cholesterol
levels and reduce the percentage of body fat in moderately
obese people, even if the exercise program does not lead
to weight loss.
The
results of the recently completed pilot study are the
first to demonstrate that exercise alone -- independent
of weight loss or diet changes -- can cut the risks
of heart disease, the researchers said. They said this
should provide encouragement to millions of overweight
Americans, many of whom quit exercise programs because
they failed to lose weight.
The
results of the three-month study by Duke cardiologist
Dr. William Kraus were published Tuesday (Feb.15) in
the February issue of the journal Clinical Exercise
Physiology.
The
study findings, which involved seven mildly obese men
and women, provided the scientific basis for a recent
$4.3 million grant from the National Heart, Lung and
Blood Institute which will allow researchers to carry
out a much larger trial. That trial, called Studies
of Targeted Risk Reduction Interventions through Defined
Exercise (STRRIDE), has been enrolling patients for
the past year.
"This
pilot study was a first attempt to isolate the effects
of exercise from weight loss in a controlled fashion,"
Kraus said. "We designed the trial such that we
can attribute all the beneficial effects to exercise
alone." Kraus is confident that the ongoing STRRIDE
study will confirm the results of the pilot study. Kraus
added that since the changes documented by the study
were consistent across all patients, the small number
of patients involved does not limit researchers' ability
to draw conclusions.
"We
now have the data for physicians who can tell their
patients that they shouldn't focus so much on the scale,"
said Kraus, who led the study. "These patients
should not become discouraged and give up exercising,
because our study shows that these patients are getting
healthier even if they don't lose any weight."
Specifically,
patients saw an average decline in the so-called "bad"
LDL cholesterol from 122 to 104, and an average increase
in the so-called "good" HDL cholesterol from
32 to 37. These changes were deemed to be statistically
significant. In addition, patients saw a 4.3 percent
decrease in body fat, which researchers say likely turned
into muscle.
The
weight of all patients remained the same during the
three-month study. In fact, if patients started losing
weight, researchers altered their diets to maintain
a constant weight.
The
patients enrolled in the trial had body mass index (BMI)
ranging from 25 to 35. It is estimated that about 55
percent of Americans have a BMI greater than 25, and
half of them have a BMI greater than 30. BMI, because
it takes into account the height of a person, is considered
the most accurate measure of obesity. It is calculated
by dividing body weight (in kilograms) by the square
of the height (in meters) -- a BMI of 30 is considered
obese, 35 is considered morbidly obese.
The
patients also had elevated cholesterol levels.
"It
is important for health policy reasons to know how much
exercise to recommend," Kraus said. "Physicians
have always recommended exercise, but there has been
no real scientific basis on how much and how intensely
one should exercise."
In
the trial, patients worked out for about one hour four
times a week using a combination of treadmill, stationary
bicycle, stair exercises and other exercise equipment.
As the trial progressed, the intensity of exercises
increased.
"This
study shows that starting a moderate exercise program
of only three months' duration -- even in the absence
of weight loss -- can have significant beneficial effects
on cardiovascular risk factors in overweight people
with elevated cholesterol levels," Kraus said.
Not
surprisingly, Kraus said, all of the patients saw a
marked increase -- 11 percent -- in their exercise tolerance,
which is attributable to the redistribution of body
fat into muscle.
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