Burning muscle. Sounds scary, huh? Has anyone ever told you that you might be doing it? Let me explain..
Okay, so, let's begin with the basics. The order in which your body uses energy is : Glucose -> Glycogen -> Fat -> Protein. The main energy source is 'glucose' and 'glycogen'. Your fat is used as the next energy source. The body rarely IF ever breaks down the protein for energy. So, basicaly, the body uses glucose as a primary energy source. Your body gets glucose by breaking down carbohydrates from your meal.
Now, if your body doesn't use up all of the glucose which you acquired, it gets stuffed (stored) down in your liver. The glucose stored in your liver is then called glycogen.Your glycogen reserves can last about six hours. After you run out of glycogen, your body starts breaking down fats to use them as energy.