For kids, reducing TV
viewing may be a key to preventing obesity
BY MITCH LESLIE
A Stanford study suggests
that, for grade-school children, watching less television
may be a key to limiting weight gain. Children who were
involved in a one-year curriculum to reduce their TV
viewing gained significantly less body fat than a control
group of their peers.
The study of 192 third-
and fourth-graders from two San Jose elementary schools
is important not only for showing a connection between TV
watching and body weight, but it is also some of the
first evidence that a behavioral program delivered in
schools can motivate children to ration their TV viewing,
said the study's author, Thomas Robinson, MD, assistant
professor of pediatrics and medicine. Robinson thinks
this program is a promising population-wide approach to
help prevent childhood obesity, which he says has reached
epidemic proportions.
"One of the things
that makes this study unique was that it focused
specifically on reducing TV, videotape and video game
viewing without promoting any other activities as
substitutes," Robinson said. "As a result, we
were able to isolate the effects of these media
alone."
Robinson presented his
results May 4 at the Pediatric Academic Societies annual
meeting in San Francisco.
American children have
become fixated on television and now spend, on average,
more than four hours a day watching TV and videos or
playing video games, according to nationwide surveys.
Only sleep consumes a larger share of the average child's
day. And more and more children and adults are now
overweight. Rates of childhood obesity have more than
doubled over the past two decades, Robinson said.
To physicians and public
health experts, this epidemic of obesity is alarming.
Overweight children tend to become overweight adults, who
are more likely to develop life-threatening health
problems like diabetes and heart disease. The amount of
time kids spend immobile in front of the TV has
frequently been blamed as a cause of obesity. That
proposal sounds eminently logical, Robinson said, but
epidemiological studies seeking a link between number of
hours watched and weight have found only a weak
relationship, he noted.
All of these studies have
looked for correlations between the TV viewing and body
weight without manipulating the amount of TV watched.
Robinson approached the problem differently by trying to
alter TV habits and then subsequently measuring the
effect on body weight. As a result, this was the first
experimental test of the TV-obesity hypothesis in normal
school children.
Local education officials
picked two schools with similar ethnic composition,
socioeconomic standing and scholastic achievement. At one
of the schools, the third- and fourth-graders received an
18-lesson program, presented by their classroom teachers
as part of the normal school curriculum, that was
designed to reduce TV and videotape watching and video
game playing. Both schools agreed to participate before
learning which school would receive the curriculum, and
the students at each school were found to have similar TV
viewing habits and body fatness at the beginning of the
school year, Robinson said.
TV-reduction lessons began
by encouraging children to keep track of how much time
they spent watching TV and videos and playing video
games. In the next step, the children were encouraged to
go 10 days without TV something that two-thirds of
them accomplished. Then the lessons turned to setting
TV-watching limits of 7 hours per week and becoming more
selective viewers.
At the beginning and the
end of the school year, pupils at both schools filled out
surveys about their media use, diet and exercise habits.
Their body fat was measured, and they took a physical
fitness test. Parents also completed interviews about
their own and their children's habits.
To account for normal
growth and maturation, Robinson compared the change in
different body measurements between the two schools over
the course of the school year. Children attending the
school that had received the TV-reduction lessons did
reduce their television watching by about one-third to
one-fourth, compared with their peers. Over the course of
the study, they also showed a significantly smaller
increase in waist size, waist-to-hip ratio and body mass
index, a measure of weight adjusted for height. For
example, the average pupil at the TV-reduction school
gained nearly 2 pounds less than the average student at
the control school.
However, the two schools
didn't differ in consumption of high-fat foods, amount of
moderate-to-vigorous exercise, or physical fitness. So if
the kids weren't exercising more or eating a healthier
diet, Robinson needed to try to account for the weight
difference. Robinson said one possibility was that the
kids were performing more low-level activities more
energetic than simply sitting still but less energetic
than walking. Freed from the TV, the children may simply
have been moving around more, though this kind of
activity is extremely difficult to measure, Robinson
said.
However, the difference
may also stem from changes in the number of meals the
kids ate in front of the TV. The children at the
TV-reduction school significantly decreased the number of
meals they ate while watching TV. Even a small change in
caloric intake could account for the difference in weight
gain, Robinson noted. For example, the calorie equivalent
of one additional regular soft drink per day translates
into a yearly weight gain of about 15 pounds, he said.
"These are the
largest effects on body composition we have seen from any
obesity prevention program we have studied to date,"
said Robinson. "But our enthusiasm has to be
tempered because the results come from only a two-school
study."
Robinson's study was
funded by a grant from the American Heart Association,
California Affiliate. He subsequently has received a
grant from the National Heart, Lung and Blood Institute
to replicate the study with 900 students from 12
elementary schools. That research has just begun and will
also involve Stanford researchers Joel D. Killen, PhD,
associate professor of medicine; Helena C. Kraemer, PhD,
professor of psychiatry and behavioral sciences; William
Haskell, PhD, professor of medicine; Leslie Pruitt, PhD,
research associate in medicine; and Donna Matheson, PhD,
a post-doctoral scholar in pediatrics. SR
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