child on a diet?

MY 11 yr old son is, according to the BMI charts, in the overweight range.  he is only 4'7", and weighs 102 lbs.  he HATES to exercise, for which we have tried various reward systems, sports, etc.  this week he will start working with a personal trainer at the gym, in hopes that for someone else, he will do the work.  my question is this, is it safe and if so, how do we go about putting him on a weght loss plan. he does not eat that poorly - we have recorded his food, and he has been to a GI dr (he holds his stool), who said we need to increase his fiber, which we have done.  still, he just seems to not grow, and to keep adding weight.  he does get some exercise - trampoline, playing with the soccer ball during his sister's games, baskeball at home, treadmill at home (after a great deal of bargaining!), but it clearly isnt enough.  so, how do i tell how many calories he needs?

thanks

[Renee Radenberg]

He is coming close to his teenage years and his body changes and grows taller. It is recommended to increase children's physical activities to loss weight, and not lower calorie intake due to the need of calories for growth. It is good he is doing some exercising. Limit time in front of the TV or non-active-video games. There have been studies showing the longer the length of time a child sit in front of the TV, the greater the weight gain. I suggest you do limit high sugar drinks/snacks and replace with milk/yogurt or fruit/popcorn/cheese. High sugar drink and snacks do not give the child nutrients they need. Thank you for your question.