I know I cannot lower my carbs past 30% of my total calories because it makes me too tired. I am an active individual, lifting weights 4x weekly and doing cardio 3-4x weekly, as well as being in soccer (however that plays into the cardio).

May I suggest Tom Venuto's 'Burn the Fat, Feed the Muscle'? I'm on that, and it is working very well for me! (: