Hi, this is my first post here on mcb, but having grown up as a chubby kid(no longer) I feel for ya so I had to throw in something that may or may not help.
You may want to look into interval training. Do a Google search for Tabata. Its the methodology of high intensity low duration interval training.
There are some issues with it however. First, its very easy to cheat it, and not be intense enough to gain the benefits. Second, its also possible to be too intense and injure yourself. So you have to find the correct medium, slowly working your way up to the proper level.
Personally I follow a workout routine called crossfit. It is another high intensity workout program that you can follow online via Welcome to CrossFit: Forging Elite Fitness
. It uses the technique high intensity, constantly varied workouts.