I have read that cardio is best done on an empty stomach for maximum fat loss. The reason being that glycogen stores are low in the morning meaning that you will burn fat for fuel. However doesn't that really just mean that you will burn more fat if you are depleted of carbs, and that if you wanted to you could eat a protein based meal (say a shake or a tuna and egg white scramble) before cardio and still burn the same amount of fat as not eating anything before? I'm just trying to understand this a little better.