It's not the amount of TV but the number of junk food commercials that may contribute towards childhood obesity, say researchers.
Principal investigator Frederick J. Zimmerman found that the association between television viewing and childhood obesity is directly related to kids' exposure to advertisements that endorse unhealthy foods.
Zimmerman and Janice F. Bell broke down the types of television programmes viewed by children to examine if different kinds of content exerted different effects on obesity.
The UCLA School of Public Health study discovered that commercial viewing was significantly associated with higher Body Mass Index among all kids.
Zimmerman said: "Commercial television pushes children to eat a large quantity of those foods they should consume least: sugary cereals, snacks, fast food and soda pop."
Non-commercial viewing, including watching DVDs or educational television programming, was observed to have no significant link with obesity, the study showed.
The authors recommended that steering children away from ommercial television may help reduce childhood obesity, onsidering food is the most commonly advertised product on children's television.
The study was published in the American Journal of Public Health.