[SunnyInc.]

Heavy weight training is an excellent way to lose weight. Not only do heavy, intense weight lifting sessions burn heaps of calories but the muscle you put on burns calories even when you're sitting on your couch watching television. If I were you I'd invest most of my time in heavy lifting and get into sprint training once you've built up a semi-decent cardio base. I don't know much about American football but I do know if you want to be fast you're going to have to do a fair chunk of running...

Edit...

I'm not suggesting you do all these, but just to give you an idea of how much a person can do with a set of dumbbells, here are a few dumbbell exercises off the top of my head:

Lateral Raises
Shoulder Press
Upright Row
Dumbbell Bench Press
Incline Dumbbell Bench Press
Decline Dumbbell Bench Press
Bench Flies
Tricep Kickbacks
Tricep Extensions
Dumbbell Rows
Bent-Over Flies
Hammer Curls
Concentration Curls
Conventional Curls
Lunges
Squats (Personally, I think that barbell sqauts are the only way to go with squats but whatever)
Calf Raises