Children who are encouraged to do more physical education at school are lazier at home and do not increase their overall activity levels, a study suggests.

Research presented at the European Congress on Obesity today suggests that those children who were given more scheduled exercise at school compensated by doing less after hours. Those who did little at school were found to be more active at home.

The scientists found that the total weekly physical activity among children attending different schools was much the same despite large differences in the amount of time allocated to PE.

The findings suggest that environmental factors are less important as stimuli for physical activity in children, and exercise is more likely to be triggered by a form of central control in the brain similar to that which regulates appetite.

Alissa Frémeaux, a biostatistician at Peninsula College of Medicine and Dentistry in Plymouth, said that this possible exercise regulator — which she described as like a thermostat for activity — should be considered in the battle with childhood obesity.

“These findings have implications for anti-obesity policies because they challenge the assumption that creating more opportunities for children to be active — by providing more playgrounds, sports facilities and more physical education time in schools — will mean more physical activity,” she said.

“If health strategists want to alter the physical activity of children, it is important that they first understand what controls it.”

The researchers studied 206 children, aged between 7 and 11, from three primary schools with different amounts of timetabled physical education. Children attending one school got on average 9.2 hours a week of scheduled PE, while those at the second school got 2.4 hours and those at the third got just 1.7 hours.

The researchers found that although the children attending the high-PE school did 40 per cent more activity during school hours than the other children, their total weekly activity was no different.

Ms Frémeaux said that though there was a range in the amount of activity the children did at each school, average activity was the same regardless.

“We discovered that the children who got a lot of PE time at school were compensating by doing less at home, while those who got very little PE time compensated by cranking up their activity at home, so that over the week, they all accumulated the same amount,” the statisician said. “We believe the range of activity among children, from the slothful to the hyperactive, reflects not the range in environmental opportunities, but the range of individual activity set-points in the brains of children.”

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