Even just 30 minutes of cardio a few days a week can give you immense improvements in your weight training workouts. If you are muscle building already at your optimum fat content you should avoid cardio. To help you build more muscle and burn off fat, certain supplements, such as whey protein and creatine are needed. By eating more often you will also help your body increase it's metabolism, which will help you lose weight. A program that is based on actual supermarket food is preferable.