with the mileage you are doing it isn't going to hurt to cut down on the carbs unless you are doing longer rides. Other threads have talked about high protien diets, (including Atkins which I don't favor and I'm not going to rehash my reasoning.) Overall, the new food pyramid does advocate a higher protein to carbohydrate ratio which sounds like that is what your doc has recommended. Be patient. Remember diet and excercise mostly lowers triglycerides and raises HDL (good cholesterol). The LDL (other bad cholesterol) for the most part is genetically determined but weight loss and excercise does help it some.