Try exercising on not very much energy (ie: empty stomach first thing in the morning), then eat some carbs and protein immediatey afterward, to help your body recover from what you just did. You won't perform as well on an empty stomach (well, duh...) but it will force your body into fat-burning mode.

I know losing fat while gaining muscle is tricky and hard to do, but it's possible if you control what and when you eat. Eat your protein when you're body is in a mode to recover and build from exercise, and control your calorie intake for the day. But don't starve yourself. If you figure out how many calories your body would use if you weren't exercising, just to stay the same weight, and then eat that, the extra calories you burn by adding exercise to the mix will help you slim down.

ps: I was 380 at my highest weight, and am around 270 right now, and falling slowly again