2003-01-15
Lead
investigator Anne McTiernan, M.D., Ph.D., a member of
Fred Hutchinson's Public Health Sciences Division, and
colleagues report the results of the largest randomized
clinical trial to assess the effect of exercise on overall
and intra-abdominal obesity in postmenopausal women in
the Jan. 15 issue of the Journal of the American Medical
Association.
Researchers from Fred Hutchinson, the University of Washington,
Yale University and the University of Colorado collaborated
on the study.
"Even if a woman who exercises regularly doesn't see
the benefits of dramatic weight loss on her scale, our results
indicate that she can feel confident that she is improving
her health, because regardless of the amount of weight lost,
we now know that exercise reduces hidden intra-abdominal
fat, the most dangerous type of fat," said McTiernan,
director of Fred Hutchinson's Prevention Center and an international
expert on the impact of physical activity on cancer prevention.
"This study gives us direct evidence that exercise
can affect biology related to cancer and other chronic
diseases
in older women."
Reducing intra-abdominal, or visceral, fat is important
because in addition to increasing the risk of cardiovascular
disease and diabetes, among other conditions, such fat can
raise insulin levels, which promotes the growth of cancer
cells.
People with high levels of intra-abdominal fat may not
even know it, McTiernan said, because it is hidden, deposited
around the internal organs within the abdomen. "Most
women don't know about intra-abdominal fat, but they
should,
since it is the most clinically significant type of fat
and it's where women tend to store fat after menopause."
Although it is known that so-called "apple-shaped"
people who store their fat around the stomach are at higher
risk for conditions such as diabetes, hypertension and stroke
than "pear-shaped" people who store their fat
in their buttocks and thighs, visceral obesity is not
necessarily
correlated with body shape, McTiernan said. The only
accurate way to determine the presence and extent of
intra-abdominal
fat is with imaging procedures such as CT or MRI scans.
"Because it is so costly to measure intra-abdominal
obesity, until now very little data has existed on the impact
of exercise on this dangerous, hidden health risk," she
said.
This yearlong study involved more than 170 previously sedentary,
overweight, postmenopausal Seattle-area women. None took
hormone-replacement therapy. Half were randomly assigned
to a moderate-intensity, aerobic-exercise group and half,
who served as a comparison group, attended a weekly hour-long
stretching class.
The members of the exercise group, who worked out at home
and at a gym for at least 45 minutes five days a week -
an amount similar to current national recommendations -
achieved significant reductions in weight, total body fat
and intra-abdominal fat. After a year on the program, while
the amount of body weight lost was modest yet statistically
significant, the exercisers lost between 3.4 percent and
6.9 percent intra-abdominal fat while maintaining their
calorie intake. Women who had the highest adherence to the
program experienced the largest decreases in weight, total
and intra-abdominal fat. The women in the stretching group,
in contrast, experienced a slight gain in intra-abdominal
fat.
"The beauty of exercise as a method to reduce total
and intra-abdominal fat - and therefore chronic disease
- is that it can be done by most women at low cost and with
low risk of side effects. In addition, exercise has many
other health benefits. The good news is that it is never
too late to enjoy the health benefits of exercise," McTiernan
said.
Strengths of this study, compared to two previous trials
that looked at the impact of activity on intra-abdominal
obesity, include its large sample size (173 versus fewer
than 25 subjects), the length of the exercise intervention
(one year compared to less than six months), and its high
adherence rates (81 percent of the exercisers completed
80 percent or more of their prescribed 225 minutes per week
of exercise).
Another strength of this study was its randomized, controlled,
clinical-trial design, considered the gold standard of study
designs in medicine. The participants met three times a
week with an exercise physiologist at an exercise facility,
where they performed treadmill walking and stationary biking.
They also exercised two days a week at home, doing exercises
of their own choosing, mostly walking.
"In this type of study, we can directly control for
extraneous factors and we directly observe what the women
are doing rather than just relying on what they report on
questionnaires. Therefore, we have more confidence in the
results," she said.
The results of the study, funded by the National Cancer
Institute, are significant for older women who seek a natural
way to reduce their risk of chronic disease, said McTiernan,
who is also a research associate professor at the University
of Washington School of Medicine and School of Public Health
and Community Medicine.
"Most American women gain one to two pounds on average
every year, and that adds up to dangerous levels over a
lifetime. All women - especially those at risk for diabetes,
cardiovascular disease, cancer or high cholesterol - need
to stop gaining weight," she said. "Regular,
moderate-intensity exercise can help keep the weight
from creeping on, which
can translate to improved health in the long run."
The
Fred Hutchinson Cancer Research Center, home of two Nobel
Prize laureates, is an independent, nonprofit research institution
dedicated to the development and advancement of biomedical
technology to eliminate cancer and other potentially fatal
diseases. Fred Hutchinson receives more funding from the National
Institutes of Health than any other independent U.S. research
center. Recognized internationally for its pioneering work
in bone-marrow transplantation, the center's four scientific
divisions collaborate to form a unique environment for conducting
basic and applied science. Fred Hutchinson is the only National
Cancer Institute-designated comprehensive cancer center in
the Pacific Northwest and is one of 41 nationwide. For more
information, visit the center's Web site at http://www.fhcrc.org.
Source:
Fred Hutchinson Cancer Research Center