I agree with Heather about food.Ban anything with artificial colours and flavours, in fact everything that is not natural. Meat, fish, cheese, eggs and vegetables are great. It would help to ban anything with grain, including bread, but that might be too difficult.
It is a long time since we had a 13 year old boy , but I know from experience that 13 is young enough to be turned round. Sometimes they are better with grandparents than with parents, so I do hope that will be your experience.
My lad wanted to join the RAAF cadets at that age, and as we are quite near to Amberley Air Base, we let him join. This channelled so much of his energy, and the whole military structure appealed to him. He loved it, especially weekend exercises in the bush, camping out. Later he joined the Australian Army reserve, when he was at university, and he is now a captain, and has just come back from 8 months in East Timor.
But - he was quite a naughty 13 year old once!!!
Good luck!