Inactivity may
be Main Factor in Girls' Obesity
July 18, 2005
Waning exercise
levels, even more than overeating, may be a major reason
that many U.S. girls become overweight as teenagers,
new study findings suggest.
In a study of nearly 2,300 girls followed for a decade,
researchers found that the proportion who were overweight
or obese doubled over time -- and declining activity
levels looked to be top reason.
Girls who remained moderately active throughout their
teen years gained anywhere from 9 to 20 pounds less
than their peers who got little or no exercise. Diet,
on the other hand, did not emerge as a key factor, as
the girls' reported calorie intakes changed little as
they got older.
"Our results provide evidence that physical activity
plays asubstantial and independent part in the rate
of gain in BMI
(body mass index) during adolescence," the study
authors write in a report published online by The Lancet
medical journal.
Teenagers' increasingly sedentary lifestyles, the researchers
add, may be a "major factor" in the sharp
increase in obesity the U.S. has seen in the past 20
years.
The implication, they say, is that getting kids to
stay moderately active -- such as walking briskly for
30 minutes on most days of the week -- could help combat
the "global obesity epidemic."
Dr. Sue Y. S. Kimm of the University of New Mexico
Health Sciences Center in Albuquerque led the study,
which followed 2,287 white and black girls from three
U.S. cities for up to 10 years, starting at the age
of 9 or 10.
Each year, the researchers recorded the girls' BMI
-- a measure of weight in relation to height -- and
used skin fold measurements to gauge their body fat.
The girls also periodically reported on their exercise
and eating habits.
Girls were considered active if their exercise habits
were at least equivalent to 30 minutes of brisk walking
per day, 5 days a week -- and were maintained throughout
adolescence. Just one-third of white girls and 11 percent
of black girls met that definition, the researchers
found.
Active girls generally had a lower BMI than their inactive
peers at the age of 9, and that difference in body mass
tripled over time, according to Kimm's team.
The effect of exercise habits was particularly pronounced
among black girls, who tended to gain more weight than
white girls did as their activity levels declined.
Diet did not appear to play a large role in the girls'
weight gain over time, since their calorie intakes changed
relatively little over time, according to the researchers.
However, they point out, calorie intakes were based
on food records that the girls kept periodically. People
in studies, particularly white women, are known to commonly
under-report their food intake, and this could underlie
the lack of calorie change seen in this study, Kimm
and her colleagues note.
Regardless, the findings on exercise have "important
implications for obesity prevention," according
to Dr. John J. Reilly of the University of Glasgow in
the UK. In an accompanying editorial, he writes that
doctors "should have no hesitation" in encouraging
exercise during adolescence -- which, besides possibly
combating excess weight gain, makes for a healthier
heart and bones.
Source: http://today.reuters.com
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