UK and US guidelines on how much physical activity children need to boost their health and stave off obesity need to be revised, conclude researchers in a study published ahead of print in the Archives of Disease in Childhood.
What's more, less than half of boys and only one in eight girls manage the recommended weekly amounts.
The researchers base their findings on the long term monitoring of 113 boys and 99 girls from 54 different schools, all of whom were 5 years old when the study started.
The children were part of the EarlyBird study, which is tracking the long term health of 307 children born between 1995 and 1996.
The children's weekly physical activity levels were measured using a tiny device worn around the waist and designed for the purpose.
And changes in weight and predictive health indicators, such as insulin resistance, blood fat and cholesterol levels, and blood pressure were measured annually between the ages of 5 and 8.
Taken together, these health indicators reflect the risk of developing cardiovascular disease and diabetes.
Both the UK and US guidelines recommend that children are moderately physically active for at least an hour every day, in a bid to stave off obesity and its attendant health risks. And they measure body mass index (weight) to monitor impact
The results showed that there was a wide range of physical activity among children, some spending as little as 10 minutes a day at the recommended intensity while others were spending over 90 minutes a day.
Around 42% of boys but only 11% of girls met the 60 minute guideline.
There was no difference in weight (BMI) change between those who did and did not meet the guidelines.
But both boys and girls who met the guidelines showed progressive improvement in their predictive health indicators, while those who did not showed a progressive deterioration.
The authors suggest that the measure used to gauge impact may simply be too crude, and that applying the same guideline to both sexes may not be appropriate.
Children who do more exercise clearly benefit, but we still have no idea how to encourage the 60% of boys and 90% of girls who do not meet the deadline to do more.