Television watching is known to raise obesity rates, both because children exercise less and because it can interfere with sleep. (CBC)

Banning fast-food advertising on television in the United States could reduce the number of overweight children by as much as 18 per cent, researchers said.

But the team at the National Bureau of Economic Research questioned whether it would be practical to impose that kind of government regulation — something done only by Sweden, Norway and Finland.

Quebec banned direct television advertising to children in 1978, but remains the only province to do so.

"We have known for some time that childhood obesity has gripped our culture, but little empirical research has been done that identifies television advertising as a possible cause," said economist Shin-Yi Chou of Lehigh University in Pennsylvania.

"Hopefully, this line of research can lead to a serious discussion about the type of policies that can curb America's obesity epidemic."

For their study, funded in part by the federal government, Chou and colleagues used data on nearly 13,000 children from the 1979 Child-Young Adult National Longitudinal Survey of Youth and the 1997 National Longitudinal Survey of Youth, both issued by the U.S. Department of Labor.

"The advertising measure used is the number of hours of spot television fast-food restaurant advertising messages seen per week," they wrote in the Journal of Law and Economics.

"Our results indicate that a ban on these advertisements would reduce the number of overweight children ages 3-11 in a fixed population by 18 per cent and would reduce the number of overweight adolescents ages 12-18 by 14 per cent."

The U.S. Centers for Disease Control and Prevention estimates these percentages of young people in various age groups are overweight:

• 13.9 per cent of children two to five years old.
• 18.8 per cent of six- to 11-year-olds.
• More than 17 per cent of 12- to 19-year-olds.

The percentages have been steadily rising in Canada and the U.S.

Countering sedentary lifestyles

In March 2007, the House of Commons standing committee on health released a report on childhood obesity in Canada that noted childhood and adolescent overweight and obesity rates have spiked over the past three decades.

In 2004, 18 per cent of children and adolescents were overweight and eight per cent were obese, the report said.

Television watching is also known to raise obesity rates, both because children exercise less and because it can interfere with sleep.

The U.S. Institute of Medicine reported in 2006 that there was compelling evidence linking food advertising on television and increased childhood obesity.

One study suggested that children viewed an average of about 20,000 commercials on television per year in the late 1970s, rising to 30,000 per year in the late 1980s and more than 40,000 per year in the late 1990s.

In April 2007, a group of food companies said they would use half of their advertising to promote healthy eating and active living among Canadian children. The Advertising Standards Canada, an independent self-regulatory body, audits the ads.

In April, a private member's bill in Ontario proposed banning all television advertising of food and drinks aimed at children under 13.

But in the internet age, marketers build environments online that kids become immersed in, building brand identity and brand loyalty, said Jane Tallim, co-executive director of the Ottawa-based Media Awareness Network.

Teaching children to be more media savvy about how advertising and companies target them would be more effective, Tallim said.

With files from Reuters and the Canadian Press