My DS nearly 12 has lost interest in sport apart from once a week footy with his mates, and is always tired. He prefers to do things sitting down like using his tablet (of course) reading, drawing crafts. We have offered him the choice of trying other sports or clubs but he doesn't want to. He has lots of friends and is doing well at school. He has just started puberty but only just. Is this hormones or something else?