Traditional diets include lots of carbs. Bodybuilders realized early that protein is good for muscle growth. So they started eating tons of protein, and reducin

Traditional diets include lots of carbs. Bodybuilders realized early that protein is good for muscle growth. So they started eating tons of protein, and reducing other macronutrients. They realized after a while that carbs can actually be cut out totally and indefinitely (which is not true of protein and fat). They discovered this because nobody else had a reason to try to eat such a strange, protein-focused diet. At least in modern societies. Of course the Inuit and other far-north peoples have known forever that one can live healthily off essentially nothing but meat.