TV ads influence childhood obesity

Studies have linked TV time to children's risk of obesity, but new findings suggest it might not be the sitting around that's the problem, but the exposure to commercials.

Researchers found that for children younger than seven, the amount of time spent watching commercial TV was related to weight gain over the next five years. But the amount of time the children spent on other sedentary activities -- such as watching videos, DVDs or commercial-free educational television -- had no effect on their weight.

Moreover, the relationship between commercial TV and weight held up when the researchers accounted for a number of other factors, including kids' physical activity and their mothers' weight and education levels.

"This study shows that only commercial viewing is associated with obesity. We think that the reasons are the effects of the pervasive food advertising on commercial television," said lead researcher Dr Frederick J. Zimmerman, of the University of California, Los Angeles.

Educational TV still ok

TV has often been "demonised" for its potential effects on children's health and development, Zimmerman said, but added that not all TV is alike.

"Educational television fosters health and strong development, while commercial television is associated with slack minds and flabby bodies," Zimmerman said.

The problem, he said, is that much of the food advertised on TV is "highly processed and full of empty kilojoules" -- that is, kilojoules that offer little to no nutritional value. Zimmerman said that parents might be able to lower their kids' risk of obesity by limiting their exposure to commercials, without having to cut out all TV programs and DVDs.

The findings, published online by the American Journal of Public Health, are based on assessments of 2 037 children in a study that ran from 1997 to 2002.

How the study was done

At the outset, when the children were age 12 or younger, parents completed questionnaires and a diary of their children's daily activities, including TV viewing, on one random school-day and one random weekend day.

They repeated the measures in 2002. The researchers found that for children aged six or younger at the outset, each hour spent watching commercial TV in 1997 was related to a slightly higher than average increase in body mass index in 2002.

Body mass index, or BMI, is a measure of weight in relation to height. Among children who were seven or older at the study's start, commercial TV viewing in 2002 was related to their BMI in 2002.

The findings support the notion that TV affects some children's weight not by keeping them on the couch, but by exposing them to promotions for junk food and fast food, according to Zimmerman's team.

"Kids who watch a lot of TV tend to become obese, Zimmerman said, "but they don't need to. This report suggests that simply by avoiding advertising on television, parents can greatly reduce their child's risk of obesity."  - (Reuters Health, December 2009)