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How Much Activity
for Weight Control?
Surveys reveal that many Americans
are confused by the conflicting messages about nutrition and
wellness that inundate magazines, newspapers and TV news programs.
Unfortunately, messages about physical activity can be just as
erratic. Fortunately, research is now providing evidence on just
how much activity is needed to stop weight gain and support weight
loss.
The STRRIDE study is one example
of researchers taking a closer look at how activity alone can
be used to combat obesity without any changes to diet. Participants
in the study (sedentary overweight and mildly obese men and women)
were assigned to one of four groups that differed in amount and
intensity of exercise. |
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Researchers saw a direct relationship
between amount of physical activity and changes in weight. After
eight months, almost 75 percent of those assigned to the no-exercise
control group gained weight. Among the exercisers, participants
needed to accumulate the equivalent of six to seven miles of
walking each week (an average of about 20 minutes a day of moderate
walking) just to prevent weight gain.
Dietary interventions in addition
to increased activity are almost always needed if someone is
looking to lose weight and maintain that leaner frame. One study
followed women who began a program to change eating and exercise
habits for two years. Those who achieved and sustained at least
a 10 percent weight loss had added about 275 minutes of moderate
activity a week to their sedentary lifestyle – the equivalent
of about 40 minutes of daily activity or 55 minutes, 5 days a
week.
In an earlier study, maintaining
weight loss took more activity than that. The study began following
over two dozen women within three months after they reached their
weight loss target. One year later, sedentary women had gained
more than 15 pounds compared to an average 5-pound gain among
women who created a physically active lifestyle. According to
the researchers, the threshold to maintain weight loss averaged
80 minutes a day of moderate activity or 35 minutes a day of
vigorous activity.
We don’t know all the reasons
for the different levels of physical activity necessary to maintain
weight loss in these and other studies. But experts speculate
that the actual activity level needed varies for each of us depending
on metabolism, how much we sit or move throughout our day’s
activities and how many calories we consume. The one consistent
finding, however, is that for almost everybody, some daily physical
activity is essential.
Inherited genetic tendencies
can also impact weight gain. Although some people may want to
give up the battle altogether if they feel their weight woes
are genetic, new research suggests that at least some inherited
tendencies may be overcome with adequate physical activity. One
study found that carriers of a common weight-related gene were
more likely to be overweight if they exhibited below average
physical activity. That same genetic variable had little impact
on weight among those with above-average activity levels.
Physical activity influences
weight by burning calories and increasing metabolic rate as muscle
tissue is built and maintained. But it may also impact weight
as part of a "constellation" of health behaviors. Since
physically active people tend to eat more healthfully, some researchers
question whether activity’s impact on stress, mood, self-image
or other factors might help support the dietary behavior changes
that are usually vital to long-term weight control. |
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