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Harvard Heart Letter | July 2008
Does fitness offset fatness?
Exercise is great at any weight, but it doesn’t erase the health effects of carrying too many pounds.
Far
too few of us are active and lean, the ideal combination for staving
off heart disease and a variety of other chronic conditions. These
days, most adults are overweight, inactive, or both. If you could be
just one — active or lean — which would be better?
Researchers
have been chasing the answer to that question for some time. Early
research suggested that exercise could cancel out the health hazards
that tag along with excess weight. It’s a comforting idea, and one that
has gotten a lot of press. But it is probably an oversimplification of
a complex connection between weight, physical activity, and health.
Flip-flop findings
A
team from the Cooper Institute for Aerobics Research in Dallas kicked
the debate into high gear in 1998 with a provocative report. The
researchers measured the body composition of 22,000 men and asked each
to complete an exhaustive treadmill test. After eight years of
follow-up, 428 of the men had died. Those who were overweight but
deemed physically fit by their performance on the treadmill test were
half as likely to have died as men who were lean but not fit. What’s
more, death rates were virtually the same among fit overweight men and
fit lean men.
Other Cooper Institute studies, some of which
included women, further supported the idea that physical fitness is
more important than weight, at least when it comes to living longer.
Not
everyone agreed. North Carolina researchers looked at death rates among
more than 5,000 men and women who took part in an early
cholesterol-lowering trial. In this group, being fit offered little
protection against the health risks linked to excess weight.
The
latest salvo comes from the Women’s Health Study, a 10-year trial of
aspirin and vitamin E among nearly 40,000 middle-aged women. As you
might expect, the odds of having a heart attack, needing bypass surgery
or angioplasty, or dying of heart disease grew with increasing weight
and with decreasing activity. In each weight category (healthy,
overweight, and obese), women who burned at least 1,000 calories a week
with exercise or physical activity were less likely to have had heart
trouble than those who were inactive. But here’s the kicker: exercise
didn’t eliminate the cardiovascular hazards of excess weight.
Earlier
work from the Women’s Health Study and the Harvard-based Nurses’ Health
Study have also come to the conclusion that exercise doesn’t erase the
health-related consequences of carrying too many pounds.
Fatty hazards
Does
any of this help answer our original question: if you could be active
or lean, which would be better? Sort of. Exercise is the single best
thing you can do for yourself to prevent or control heart disease,
diabetes, osteoporosis, gallstones, depression, and a host of other
physical woes. That’s true whether your weight is squarely in the
normal range or your belly and backside are rounding out from extra
pounds you’ve accumulated over the years.
But that doesn’t
mean striving for a healthy weight should take a backseat to exercise.
Most “excess weight” is fat, not muscle or bone. Body fat isn’t an
inert layer of insulation or extra storage. It’s active tissue that
pumps out free fatty acids, hormones, growth factors, and substances
that fire up inflammation. This is especially true for fat that
accumulates around the waist. The byproducts of body fat can hasten the
onset or development of heart disease, diabetes, and kidney disease,
regardless of exercise or physical fitness.
Do both
Consider
exercise and a healthy weight to be partners in your efforts to stay
healthy or get healthy. Physical activity and weight loss (when needed)
improve the flexibility of arteries. They lower blood pressure and
improve cholesterol levels. They ease inflammation throughout the body.
And they make blood less likely to form clots inside arteries, which
can trigger heart attacks and strokes. Exercise helps you lose or
maintain weight, while losing weight can give you more energy and
mobility for exercise.
This doesn’t mean you need to run
marathons. Walking for at least 30 minutes a day is great. Walking for
longer, or doing something more intense, is even better. You don’t need
to instantly slim down to what’s considered to be a healthy weight,
either. If you are overweight, losing just 5% to 10% of your weight
will start you on the road to better health.
Tall people
tend to be heavier than short people, so doctors use the body mass
index (BMI), a measure of weight for height. (To calculate your BMI,
visit health.harvard.edu/125.)
Overweight is defined as a BMI over 25; obesity is defined as a BMI
over 30. A large waist — over 40 inches in a man or 35 inches in a
woman — is worrisome, too.
Working out is a key
ingredient for good health. So is aiming for, or keeping, a healthy
weight. Put them together and you optimize your chances of having the
healthiest and longest life possible.
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