After eight hours of having the last meal, the body enters into the fasting state as it takes that much time period to complete digestion and absorbs all the nutrients. At this time period, the body uses carbohydrates stores as its energy resource.
After overnight fasting, the body will use up mostly liver glycogen stores. After fasting 23 hours, 50 percent of muscle glycogen was reduced. In prolonged fasting, the body starts to break down muscles to use protein for energy.