Preschool-aged children in a Scottish study who participated in regular exercise sessions did develop better motor and movement skills than children who did not.
But they were no less likely to become overweight during the yearlong study than more sedentary children.
Participation in organized exercise also did not appear to promote more activity during free play.
Researchers from the University of Glasgow concluded that programs that focus on physical activity alone are not likely to have a significant impact on in very young children.
But two childhood fitness experts who spoke to WebMD remain convinced that promoting physical activity early on has lasting benefits, even if studies don't show it.
"Not proving an effect is not the same thing as proving the absence of an effect," says Andrew Gregory, MD, who is an assistant professor of orthopaedics and pediatrics at Vanderbilt University Medical Center.
"It is clear that the earlier children establish a pattern of physical activity, the more likely they are to remain active throughout childhood and into adulthood."
Jorge Gomez, MD, says it just makes sense that young children who are active will have a better shot at remaining active and fit later in life.
"It is like reading," he says. "We know that preschoolers who get read to a lot are more likely to love reading when they get to middle school or high school," he says.
Exercisers Were Not Thinner
The Scottish study included 545 preschool children, whose average age was 4. All of the children attended one of 36 day care nurseries in Glasgow.
Roughly half of the children were chosen to participate in the organized exercise program, consisting of three, 30-minute, nursery school-based exercise sessions a week for six months. Their parents were also given guidance on increasing physical activity at home and minimizing TV time.
The other children in the study received none of these interventions.
Study researcher John J. Reilly and colleagues concluded that the increased level of exercise had little effect on the children's weight or on the amount of exercise the children got at six months and 12 months after the study.
"Successful interventions to preventin early childhood may require changes not just at nursery school and home but in the wider environment," they write. "Changes in other behaviors, including diet, may also be necessary."
Parents Need to Move, Too
Last spring the American Academy of Pediatrics released a position statement on physical activity and childhood obesity, which called for the promotion of unorganized free play time for preschool-aged children.
Gregory and Gomez were two of the authors of the position statement. Among the specific recommendations for children of all ages:
- Children should be engaged in physical activity -- either organized or free play - for at least one hour a day.
- Screen time -- including TV, computers, and electronic games -- should be limited to less than two hours a day.
- Parents should set a good example by being physically active themselves.
"A parent can't say, ‘You have to do this, but I'm going to watch TV.' That won't work," Gregory says. "And physical activity has to be fun. If it isn't fun, kids aren't going to do it."
Gomez says very young children need to be given the opportunity to be physically active, but they don't need highly structured play.
"I am of the opinion that we have failed to emphasize the importance of free play," he says. "Kids are naturally active. You don't have to tell them what to do. You just have to provide the time and a safe environment and they will do the rest."
He adds that young children should spend as much time as possible outside, assuming that they are supervised and have a safe place to play.