Young boys may need to exercise differently from girls if rising levels of childhood obesity are to be curbed, new research suggests.
Researchers from the school of Physiotherapy at Trinity College Dublin found that one in five children aged between seven and 10 are overweight, while 6 per cent of those studied were obese.
More boys than girls were obese. The authors said they were concerned at the high numbers who were overweight despite their young age.
In a survey of 224 children aged seven-10 years old, attending 12 schools in the greater Dublin area, boys were found to take part in more than one hour of vigorous or hard daily physical activity.
The survey found that girls spent half this time in hard exercise.
Ms Juliette Hussey and her colleagues measured fitness and physical activity levels as well as body composition in all the schoolchildren.
While boys tended to be more physically fit than girls, the amount of hard exercise taken regularly had a direct impact only on the boys' weight.
Unlike the girls, the boys who did the least intensive exercise were the fattest, suggesting that the impact of exercise on body fat differs for boys and girls.
"The results suggest that boys and girls need to do different exercise. Boys need to exercise for longer durations and the intensity needs to be greater," Ms Hussey, lecturer in physiotherapy said.
She suggested that girls needed to undertake about 90 minutes of at least moderate exercise per day, while boys needed 120 minutes per day.
Calling for more prescriptive exercise plans for children, Ms Hussey said it was probably time to fine tune recommendations so that boys and girls were dealt with separately.
"There is a need for more research to find the quantity and intensity of exercise needed by children and to develop recommendations based on this research that can be easily understood by parents and children," she said.
The study, published in the current issue of the British Journal of Sports Medicine, found that overweight and obesity levels among Irish children was higher than children of the same age in Poland and France.
In Poland, 15.4 per cent of seven-10 year olds are overweight, with 3.6 per cent reported to be obese.
Commenting on the clinical implications of the findings, the authors said: "Body Mass Index (BMI) alone has limitations for assessing overweight people and relatively simple measures such as waist circumference and perhaps fitness, may give a clearer picture of health risks."
Noting the scientific evidence that levels of physical activity in children are related to increased risk of cardiovascular disease, the authors conclude that boys and girls should have their fitness levels regularly assessed in schools.