Humans can utilize either fat or carbohydrate for energy, with protein primarily serving as building blocks and only being converted to glucose through gluconeogenesis when necessary.

“humans don't run on protein we run on fat or carbohydrate we're like a car diesel or gas the crazy thing about humans is we can run on either and generally we use protein as building blocks and if we want to we can go through this kind of clunky difficult molecular process to turn protein into glucose called gluconeogenesis and we can use that for energy but we really use amino acids in human metabolism for energy”