Overweight Child

Short is overweight. He is 9 years old and weighs 108 lbs....he weighs 3 lbs more then Grande who is 19 yrs old!!! I'm not quite sure either why he is overweight. He doesn't eat alot, but what he eats must be the wrong things. Plus he is a video game/computer junkie so that doesn't help! I thought for sure that once he started playing basketball in December he would slim down but he hasn't. I notice too when he is playing basketball that he gets out of breath. He also sweats alot. The doctor suggested things like no food after 6pm, drink only water, etc., we tried that for awhile and it didn't make any difference. Tall went through a chubby phase when he was in 8th grade but it didn't last but a year, but Short has been having weight problems now for the past 2 years.
Has anyone else had an overweight child? Have any suggestions?