To win the war against weight gain, it turns out that every
skirmish matters as long as the physical activity puts your heart and lungs to
In a new study published today in the American Journal of
Health Promotion, University of Utah researchers found that even brief episodes
of physical activity that exceed a certain level of intensity can have as
positive an effect on weight as does the current recommendation of 10 or more
minutes at a time.
"What we learned is that for preventing weight gain,
the intensity of the activity matters more than duration," says Jessie X.
Fan, professor of family and consumer studies at the University. "This new
understanding is important because fewer than 5% of American adults today
achieve the recommended level of physical activity in a week according to the
current physical activity guidelines. Knowing that even short bouts of 'brisk'
activity can add up to a positive effect is an encouraging message for
promoting better health."
A positive health difference
The current physical activity guideline for Americans is to
get at least 150 minutes of moderate to vigorous physical activity, MVPA, a
week, which can be accumulated in eight to 10 minute periods. MVPA is defined
as greater than 2 020 counts per minute measured with a tool called an
For an average person in an everyday setting without a fancy
gadget to gauge the exertion, that would translate roughly to a walking speed
of about three mph (4.8 km/h). But taking the stairs, parking at the far end of the lot,
and walking to the store or between errands are choices that can add up and can
make a positive health difference, the researchers note.
The study shows that higher-intensity activity was
associated with a lower risk of obesity, whether in "bouts" of fewer
or greater than 10 minutes.
This may be especially important news for women, who were on
average less physically active than men. However, neither men nor women came
close to the weekly 150-minute recommendation with bouts of eight to 10
minutes. However, when adding shorter bouts of higher-intensity activity, men
exceeded the recommendation on average, accumulating 246 minutes per week, and
women came close, at 144 minutes per week on average. The message is: a little
more effort can have an important health payback.
Subjects for the study were drawn from the National Health
and Nutrition Examination Survey, NHANES, a national program that has been
collecting health and nutrition data from a representative sample of adults and
children in the United States since 1999.
From 2003 to 2006, participants in the survey wore
accelerometers for seven days, which captured data on their physical activity.
This information was in addition to the broad range of demographic and
health-related information collected in the NHANES program from interviews and
For this study, participants from 18 to 64 years of age were
drawn from the database. There were some exclusions, including pregnancy or
impairments that compromised participants' ability to walk, such as being
wheelchair bound. The final sample size for the current study was 2 202 women
and 2 309 men.
Researchers compared measurements of physical activity based
on length of time and intensity. Four categories were created: higher-intensity
bouts (greater than 10 minutes exertion at greater than 2 020 counts per
minutes, or CPM), higher-intensity short bouts (less than 10 minutes at greater
than 2 020 CPM), lower-intensity long bouts (greater than 10 minutes and less
than 2 019 CPM), and lower-intensity short bouts (less than 10 minutes and less
than 2 019 CPM).
The study used body mass index, BMI, to measure weight
status. BMI is a standard formula calculated using an individual's weight
adjusted for height, and is used as an indicator of healthy weight. A BMI
between 18.5 and 24.9 is considered normal weight, whereas a BMI between 25 and
29.9 is overweight; and over 30 is obese.
Results show that for women, each daily minute spent in
higher-intensity short bouts was related to a decrease of 0.07 BMI. Looking at
it another way, each such minute offset the calorie equivalent of 0.41 pounds.
This means that when comparing two women each 5-feet-5-inch
tall, the woman who regularly adds a minute of brisk activity to her day will
weigh nearly a half-pound less. Results were similar for men. Importantly for
both, each daily minute of higher-intensity activity lowered the odds of obesity
5% for women, and 2% for men.