As with any exercise program, unless you are specifically trying to lose weight, you will have to increase you caloric intake to maintain a balance. Also, if you are not taking enough in, it will hamper your progress. I know when I'm in a high training phase I'll expend in excess of 1000 calories a day just in my work out so I tend to eat a lot more than normal. Just make sure you are eating the right things and you shouldn't have a problem maintaining your ideal weight.