Sept. 13, 2005 -- Want to help children avoid being overweight? Limiting their TV hours may help.
New Zealand researchers followed nearly 1,000 children, starting when the kids were 3 years old and ending at age 15.
The kids who watched the most TV were most likely to be overweight. That was especially true of girls, the study shows.
"Television viewing should be regarded as an important contributing factor to childhood obesity," write the researchers in the International Journal of Obesity.
The researchers included Robert Hancox, MD, MRCP, FRACP. He is the deputy director of the Dunedin Multidisciplinary Health & Development Research Unit at New Zealand's University of Otago.
The study included kids born in New Zealand in the early 1970s. Back then, New Zealand had two TV channels, both of which had limited hours.
The kids averaged 2.3 hours of nightly TV time from ages 5 to 15. That's based on parents' reports when the kids were little and kids' own reports as teens.
Since then, kids' opportunities for "screen time" has soared with more channels, nonstop TV, computers, and DVDs, write Hancox and colleagues. They used BMI (body mass index) -- an indicator of body fat -- to identify obese and overweight kids.
TV Not Totally to Blame
The researchers don't totally blame TV for kids' extra pounds. A "complex mix" of genetic and environmental factors are probably involved, write the researchers.
"This huge increase at the population level must be largely driven by changes in children's diet or levels of activity. Time spent watching television may be related to both," they write.
The link between TV and childhood weight problems was "small," the researchers say. That could have been because of the kids' viewing habits.
TV Widely Watched
Ideally, the researchers would have compared kids who watch tons of TV with those who never watch TV.
But there was a hitch with that. The researchers didn't have a group of kids that was unexposed to TV, and less than 7% of the kids reportedly watched less than an hour of TV per night.
Had there been a group of kids that never watched TV, the link between TV viewing habits and kids' BMI might have been stronger, write the researchers.
"Even those who watched very little may have been indirectly influenced by television through its effects on their peer group," write Hancox and colleagues.
"Television has altered what is regarded as 'normal' childhood behavior," they continue. "It is difficult to play team sports after school if your potential teammates are indoors watching television."