London - When they refuse to get up from the sofa, it is easy to dismiss teenagers as being lazy.
But their lethargy might be no fault of their own.
Instead, the biological changes of puberty might actually be draining their energy and leaving them less interested in exercise than before, a study claims.
Exeter University medical school researcher Brad Metcalf analysed data on almost 300 British schoolchildren, who were tracked from the ages of five to 15.
This included information on exercise levels, collected once a year from a movement-measuring device worn on their waist.
The analysis showed that activity levels started to fall from the age of nine – when some of the children would have started puberty.
As in previous studies, the girls were found to do less exercise than the boys. But the European Congress on Obesity also heard that the drop in activity levels was sharper among the girls than the boys.
Crucially, the children were as likely to opt out of exercise during school hours as at home.
This is important, as if adolescents were purely being lazy, you would expect exercise levels to fall most sharply during evenings and weekends, when they are free from the structure of the school day.
The analysis also showed that the transition from primary to secondary school had little effect on the amount of exercise done.
Metcalf said: “It isn’t definitive but it is about making people aware that it is possible that teenagers are not inactive because they are lazy, although some might be.”
Metcalf isn’t sure what the biological process is but said it’s possible that the adolescent body conserves energy for growth and making muscle.
Tam Fry, of the Child Growth Foundation, called the results “striking” and said that although the explanation might be speculative, it should be not be dismissed. - Daily Mail