Researchers found that each hour the children played video games or watched television doubled the likelihood that the child was obese. Other factors that increased the risk of childhood obesity to a lesser extent were having a mother who worked outside the home or a father who smoked. The researchers speculate that unsupervised children may be more likely to eat large quantities of snack food after school. They also add that parental smoking may reflect a less health-conscious family environment.

Factors that lowered the risk of obesity among the children included physical activity and eating breakfast.

Dr. Katherine Morrison, co-author of the study, worked with researchers from McMaster and California State University, Fullerton. She is an associate professor of pediatrics for McMaster University's Michael G. DeGroote School of Medicine and a pediatric endocrinologist with the McMaster Children's Hospital.

Her team's findings are serious, given the rise in videogame addictions, she said.

"This is an important phenomenon to understand. We are seeing that some children and teens develop serious addiction-like symptoms to video games," said Morrison. "It affects a vulnerable population of children and youth, can impact social interactions amongst youth and, as our research shows, can drive health issues."

The results can be confusing. Evelina Krieger, a pediatrician at Allegheny General Hospital, offers some perspective:

If the children in the Canadian study spent the hour-plus they spend each day playing active video games without snacking, they'd lose 0.7 pounds a week, she said.

But the exercise they get playing active video games "is sort of equivalent to slowly walking," Dr. Krieger said. It's nowhere near the exercise children get when they are outside, running, jumping and playing, she said.

The key advice for parents is to limit the total time children indoors with electronic devices and "get them outside," she said.