May 28, 2012 5:02 AM
May 28, 2012 -- Kids who like to be active can influence others to do the same, or at least that's what new research finds.
Children in social groups that included others who were physically active were six times more likely to be physically active themselves in a study published today in the journal Pediatrics.
When researchers directly measured activity levels among children attending after-school programs in Nashville, Tenn., they found the activity level of their closest peers to be the strongest influence on the amount of time the children spent engaged in physical activity.
Nearly 1 in 5 kids in the U.S. is obese, compared to less than 1 in 10 just three decades ago.
Lack of exercise is a major contributor to the childhood obesity epidemic, and researchers say the new findings have implications for health policymakers who want to get children moving.
"We know that most obesity interventions do not work, which is why preventing obesity in the first place is so important," says researcher Sabina B. Gesell, PhD, of Vanderbilt University School of Medicine in Nashville.
"This research suggests that if we consider friendship networks in our efforts to prevent childhood obesity, we are likely to see gains that we have not seen with other interventions."
The study builds on earlier work suggesting that social networks have a big impact on body weight in adults.
Research finding that obesity spreads from friend to friend made headlines several years ago, and the idea remains controversial.
The new study is one of the first to examine the impact of social networks on activity levels in children.
Using a motion-sensing device known as an accelerometer, the Vanderbilt researchers measured activity among 81 mostly elementary school-aged children over a three-month period while they were attending after-school programs.
They also interviewed the children to determine who they spent the most time with during these after-school hours.
The children tended to group by gender, race, age, and where they went to school, but not by activity level, Gesell tells WebMD.
Active kids were no more likely to have a lot of friends than kids who were more sedentary.
But when they examined activity levels during free time, the researchers found that children adjusted their activity levels to match those of their closest peers.
"Children became either more active or more sedentary as they emulated the behaviors of those in their immediate network," the researchers write.
Sociologist Mark Pachucki, PhD, of the University of California, is studying how social networks influence eating behaviors in children and teens. He was not involved in the new study.
His earlier work in adults found that friends tend to share similar eating patterns.
"Social networks haven't been thought of as a health behavior, but that is changing," he says.
He says the early research suggests that children who spend time with friends who model desired behaviors tend to imitate these behaviors.
"A child who is an average basketball player should be playing with kids who are better than they are," he says. "By the same token, kids who don't exercise or eat well may benefit from hanging out with kids who do."