Based on the activity level in the most active kids, Andersen and colleagues write that "achieving 90 minutes of daily physical activity might be necessary for children to prevent, which seems to be the central feature for the clustering of cardiovascular disease risk factors."
A journal editorial notes that the "amount and type of physical activity needed in childhood and adolescence is still a matter of debate."
But at least an hour "or even more on the basis of Andersen's study, seems to be appropriate," write the editorialists. They include Ram Weiss, MD, PhD, senior pediatric endocrinologist at Jerusalem's Hadassah Hebrew University School of Medicine.
It would be easier for kids to reach that goal if physical activity was part of school schedules, write Weiss and colleagues.
Fitness Is the Key
The study's results were "similar for lean and overweight children," the editorialists point out.
That means physical activity doesn't just affect kids' weight. Being active appears to have other favorable effects against heart disease risk factors, write Weiss and colleagues.
Andersen's study has some limits. The children were studied only briefly. So it's not clear which kids, if any, grew up to have heart disease, or which came first: better heart health or higher physical activity levels.
Still, the study was "well-designed," with objective data from the accelerometers, note Weiss and colleagues.