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NO PAIN NO GAIN
"It now appears
that there is also a long-term beneficial effect from regular
exercise, most likely due to the fact that a significant amount of
fat is lost."
Duke
University Medical Center researchers have shown that long-term,
intensive exercise can significantly improve the body's ability to
control blood sugar levels, adding further evidence that exercise
can forestall the development of diabetes or cardiovascular
disease in at-risk patients.
Furthermore,
the researchers report, these beneficial effects of exercise were
maintained one month after the cessation of exercise. Previous
studies have shown that a single bout of exercise can improve
glucose metabolism immediately after exercise; however, the Duke
researchers say, the previously reported short-term effect
disappears within 24 hours.
"It
now appears that there is also a long-term beneficial effect from
regular exercise, most likely due to the fact that a significant
amount of fat is lost," said exercise physiologist Cris
Slentz, Ph.D., author of a study appearing Feb.15 in the journal
Clinical Exercise Physiology. "Long-term exercise leads to
loss of fat in the gut (stomach) region, which is especially
beneficial since this fat is thought to be directly linked to
increased risk of diabetes and heart disease."
The
Duke researchers wanted to see how exercise influenced the way the
body metabolized carbohydrates like glucose in people who had not
yet developed diabetes, but were at high risk. Previous studies
were not only short-term, but were conducted with elite or
well-trained athletes who are not representative of the general
population. The current study is the first of its kind using a
"real-life" population of participants, the researchers
said.
For
their study, the Duke researchers put five overweight and
sedentary people on an intensive exercise regimen for nine months,
followed by a one-month "de-training" period. They
measured blood levels of glucose and insulin before the exercise
training began, as well as one day, five days and 30 days after
the training ended. To keep these results from being influenced by
what the patients consumed, the blood samples were taken after
eight-hour fasts.
Insulin,
a hormone that is secreted by the pancreas after eating, is
responsible for the regulation of glucose levels in the blood;
excessive amounts of insulin can, over time, lead to the
complications associated with diabetes and heart disease.
"Insulin
sensitivity, or its ability to stimulate glucose metabolism, was
higher after nine months of exercise, and the fasting insulin
levels were lower," Slentz said. "Just as importantly,
30 days after stopping exercise, insulin sensitivity was still 24
percent higher than pre-exercise levels, indicating that
beneficial effects of exercise persisted."
The
Duke study was supported by a grant from the National Institutes
of Health (NIH).
"These
results provide strong evidence that long-term exercise training
can lead to both short- and long-term improvements in carbohydrate
metabolism," said cardiologist Dr. William Kraus, senior
member of the research team. "This demonstrates the clinical
significance of regular exercise in preventing the development of
insulin resistance and glucose intolerance in patients at risk for
diabetes and heart disease."
Patients
in the study did lose minimal amounts of weight (fat tissue weighs
less than muscle tissue), demonstrating that weight alone is not
necessarily a good marker for the risk of diabetes or heart
disease.
Not
surprisingly, the researchers added, the five patients also saw
marked improvements in blood cholesterol levels and exercise
capacity.
The
exercise regimen was divided into two parts. The first three
months consisted of four exercise sessions a week, beginning with
15 minutes each day and increasing to 60-70 minutes daily by the
end of the three-month period. For the remaining six months,
patients maintained the same exercise intensity and duration. The
exercise program consisted of a combination of stationary biking,
treadmill walking and stair climbing.
"For
these people, the amount of exercise was the equivalent of running
20 miles per week, so we're talking about a large amount of
exercise training," Kraus said. "Our ultimate goal is to
determine how much exercise does someone need to achieve the
maximum beneficial health effects. The prevailing advice seems to
be just do something, anything. I think we can do better than that
and come up with exercise guidelines or recommendations that are
actually based on concrete data. We still do not have good data on
how often and at what intensity is ideal for reducing the chances
of developing diabetes or heart disease." Journal
Clinical Exercise Physiology Feb 15, 2002
================================
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