Instead, you'll cannibalize muscle mass, which in turn reduces your metabolism (i.e. the calories you burn around the clock just to stay alive).
The weight training will keep your muscles stimulated and make sure you don't cannibalize your muscle mass while cutting calories, and may even boost your metabolism -- meaning you'll burn more calories even as you sleep.
However, this is balancing on the razor's edge in that you could cannibalize some muscle tissue in the process; chug a pure protein drink (no carbs) and a fistful of fish oil capsules before you leave for the gym to prevent this.
