Exercise has
innumerable health benefits, but losing weight may not be among them. A
provocative new study shows that a substantial number of people who take
up an exercise regimen wind up heavier afterward than they were at the
start, with the weight gain due mostly to extra fat, not muscle.
But the study also
finds, for the first time, that one simple strategy may improve people’s
odds of actually dropping pounds with exercise.
As we all know, the
fundamentals of weight loss should be simple. Burn more calories on any
given day than you consume and, over time, you will lose weight.
Theoretically, we can achieve that desirable condition by reducing the
number of calories that we take in through dieting or by increasing the
number of calories that we incinerate through exercise.
But in reality, most people do not achieve or sustain weight loss, no matter what method they try.
Exercise is particularly problematic in this regard. A recent review of studies
related to exercise and weight control found that in most of the
studies, people lost barely a third as many pounds as would have been
expected, given how many calories they were burning during workouts.
Many studies also report enormous variations in how people’s waistlines
respond to the same exercise program, with some people dropping pounds
and others gaining fat.
Scientists have had
little understanding, however, of why exercise helps some people but not
others to shed pounds or whether there might be early indications of
how people will respond to an exercise routine.
So for the new study,
which was published last month in The Journal of Strength and
Conditioning Research, scientists at Arizona State University in Phoenix
recruited 81 healthy but sedentary adult women. All of the women were
overweight, based on their body mass index, but some were significantly
heavier than others. None had exercised regularly in the past year.
The women were told
that they would be joining a fitness study and would exercise in order
to improve their aerobic endurance. The scientists asked the women not
to change their eating habits in any way.
Each of the volunteers
visited the physiology lab at the start of the study and the scientists
determined their weight, B.M.I., percentage of body fat, current
endurance level, and others measures of health and fitness.
Then each woman began a
supervised exercise program designed to be vigorous but manageable by
most people, said Glenn Gaesser, a professor of nutrition and health
promotion at Arizona State and senior author of the study. The women
walked on treadmills at the laboratory three times per week for 30
minutes at a pace that represented about 80 percent of their maximum
endurance.
They continued the
program for 12 weeks, with the scientists repeating the original fitness
and other tests every month during that time.
At the end of 12
weeks, the women were all significantly more aerobically fit than they
had been at the start. But many were fatter. Almost 70 percent of the
women had added at least some fat mass during the program, and several
had gained as much as 10 pounds, most of which was from fat, not added
muscle.
A few of the women,
though, had lost that much fat or more, and quite a few had remained at
the same weight as at the start of the regimen.
At this point, the
researchers returned to the data from the first day of the study, to
determine whether any obvious differences existed between the women who
subsequently gained or lost weight. “Some past studies of dieting had
indicated that women who weigh more at the beginning” of a weight-loss
program “tend to lose more weight during the program,” Dr. Gaesser said.
But the researchers
found no correlation in this case between a woman’s weight at the start
and end of the study. In fact, the scientists found no connection
between any of the original parameters of health and fitness and the
women’s responses to the exercise program.
But looking deeper
into their data, they discovered one interesting indicator: Those women
who were losing weight after four weeks of exercise tended to continue
to lose weight, while the others did not.
“What that means in
practical terms is that someone who wants to lose weight with exercise”
should step on the bathroom scale after a month, Dr. Gaesser said. If at
that point your weight remains stubbornly unchanged or has increased,
“look closely at your diet and other activities,” he said.
While this study
didn’t track the women’s eating and movement habits away from the lab,
it is likely that those who gained weight began eating more and moving
less when they weren’t on the treadmills, “probably without meaning to,”
Dr. Gaesser said.
Of course, the study
was fairly short-term. It also did not involve men, although some past
studies indicate that men, like women, frequently add fat mass after
starting to exercise.
Still, the results,
while sobering in some respects, also provide encouragement. By
deploying a bathroom scale and discipline, along with exercise, you may
well lose weight, Dr. Gaesser said.
Even more important,
the women in the study were much fitter after four months of exercise,
and Dr. Gaesser said “fitness matters far more for health than how much
you weigh.”
0 comments:
Post a Comment