Researchers at Johns Hopkins have determined that in
people age 55 to 75, a moderate program of physical
exercise can significantly offset the potentially deadly
mix of risk factors for heart disease and diabetes known as
the metabolic syndrome. More specifically, the researchers
found that exercise improved overall fitness, but the 23
percent fewer cases were more strongly linked to reductions
in total and abdominal body fat and increases in muscle
leanness rather than improved fitness.
The researchers' findings raise the importance of
physical exercise in treating both men and women with the
metabolic syndrome, a clustering of three or more risk
factors that make it more likely for a person to develop
heart disease, diabetes and stroke — including high
blood pressure, elevated blood glucose levels, excess
abdominal fat and abnormal cholesterol levels.
The study, published in the January American
Journal of Preventive Medicine, is believed to be the
first to focus on the role of exercise training in treating
metabolic syndrome in older persons, a group at high risk
for heart disease and diabetes.
"Older people are very prone to have the metabolic
syndrome," said lead study investigator and exercise
physiologist Kerry Stewart, professor of medicine and
director of clinical exercise physiology and heart health
programs at the
School of Medicine and its Heart Institute. "While each
component of metabolic syndrome increases disease risk by
itself, when combined, they represent an even greater risk
for developing heart disease, diabetes and stroke."
To assess the benefits of a fixed program of exercise
training, the Johns Hopkins team studied a group of 104
older people for a six-month period between July 1999 and
November 2003. All the participants had no previous signs
of cardiovascular disease beyond untreated mild
hypertension. One-half of the study participants were
randomly assigned to a control group that received a
booklet that encouraged increased activity, such as
walking, to promote good health. The other half
participated in a supervised series of exercises for 60
minutes three times per week. The combination of exercises
was designed to work all major muscle groups, the heart and
circulation. These included aerobics on a treadmill,
bicycle or stepper, plus weightlifting.
The Johns Hopkins team measured the changes in
participants' risk factors, body fat, and muscle and
fitness levels, and found substantial improvements in the
group that had been exercising for six months. Aerobic
fitness, as measured by peak oxygen uptake on a treadmill,
increased by 16 percent, and strength fitness increased by
17 percent. The average weight loss in this group was only
four pounds because much of the loss of fat was offset by
increased muscle mass. The fat in the abdominal region, by
itself an important risk factor for heart and metabolic
syndrome, was reduced by 20 percent among people in the
exercising group. The group that was not exercising had
either no or significantly less improvement than the
exercising group.
At the beginning of the study, 43 percent of all
participants had the metabolic syndrome. By the end of the
study, participants in the exercising group had no new
cases of metabolic syndrome, and the condition had resolved
in nine of them, a reduction of 41 percent. In the control
group, eight participants no longer had the syndrome, while
four new cases appeared, resulting in an overall reduction
of only 18 percent.
"Older people can benefit greatly from exercise,
especially to reduce their risk for developing metabolic
syndrome," Stewart said. "Our results show that this
population can be motivated to follow through with a
moderate exercise program, and for some risk factors, such
as abdominal fat, exercise can be as effective as what is
accomplished today with drugs.
"A novel finding of our study was that the changes in
disease risk factors with exercise training were more
closely related to reductions in body fat, particularly
abdominal fat, and increases in muscle tissue rather than
improvements in fitness.
"The results also confirm the value of exercise for
managing multiple risk factors. Because so many older
persons have or are at risk for metabolic syndrome, this
study provides a very strong reason for individuals to
increase their physical activity levels. They will reduce
their fatness, and increase their fitness and leanness,
while reducing their risk for heart disease and
diabetes."
Estimates of the prevalence of metabolic syndrome
range from 25 percent to 40 percent of American adults age
40 and older.
Funding for the study was provided by the Heart, Lung
and Blood Institute, a member of the National Institutes of
Health, with additional assistance from the Johns Hopkins
Bayview General Clinical Research Center, also funded by
the NIH. Other Johns Hopkins researchers who took part in
this study were Anita Bacher, Katherine Turner, Jimmy Lin,
Paul Hees, Edward Shapiro, Matthew Tayback and Pamela
Ouyang.