I wouldn't worry, with that level of exercise. There are folks who burn 700-800 calories per day just doing their jobs, if not more. What really matters is that you're getting enough protein (first and foremost), and not burning off more calories than you consume. My doctor always maintained that we lose weight on our metabolism -- meaning that we always fuel ourselves enough to cover our exercise, and whatever weight we lost would therefore be lost based on the calorie deficit our BMR causes. So you've got a real big cushion before you have to start worrying about that!