You need carbs and fat, but protein is much more important. The only problem is when people take in too much and become lethargic. Strength is increased by work against high resistance strength training and resistance training are synonymous.
Well, carbohydrates are the premium fuel, to make a clear distintion between nutrients that are buiding materials, and nutritients that are fuel. Proteins,vitamins, minerals and essential fats are predominantly buiding materials. Carbohydrate is always the limiting fuel, because no matter hoe lean athletes are, they have fat calories to spare. The body uses variable amounts of fat during extended exercise, depending on biochemical individuality, blod oxigen levels, blood free fatty acid levels, and conditioning. But you never have to worry about runing out.With carbs however, you can run out in a heartbeat. What is very important is timimg of carbohydrate intake and how much carbs? such as carbs before exercise, carb during and after trainings. Your training should always end on a physiological and psychological high. You cannot achive this goal without the proper carbs. The point is, your training and your crbs nutrition must be designed to fit your body exactly.
Regarding proten, how much protein? well long as you body has psitive nitrogen balance you are OK, a positive nitrogen balance means that the body is obtaining sufficient protein from diet. Despite what the supplement ads imply, it is not protein intake that controls muscle growth, but rather the demand for growth caused by the trauma of intense exercise. Muscle grow from pushing poudage period. So the trick is to match your individual protein intake to your training program. If, and only if you are doing intense strength or speed workouts over 3 hours per day.than there is evedence that very high protein intake does yield greater muscle growt.