I personally don't think that carbs are such a terrible thing. They're a great source of energy. Just make sure you try to steer clear of too many empty carbs that come from sugars. They burn too fast and make you feel kind of crummy when they wear off while training. Compex carbohydrates seem to fuel you better over the longer stretches of a worker. Protein is going to be necessary to help rebuild muscles in between workouts. I think the main thing is to eat a balanced diet and keep close track of your caloric intake.

Adam's absolutely right though. If you put on muscle, your overall body weight is going to go up, not down. Even if you do trim off the excess fat (except in the case of a person whose got a lot of fat to loose). Like he said, muscle weighs about three times as much as fat so if you're looking to come down in weight, you'll need be very careful about building muscle.