If you go without eating for hours or days, the contents of your stomach have been broken up into so many components, you continue to move and work. You already know that it will be some time before the fat power rolls around. The belly battery is empty, yet still we move. There must be another way to store power in the body. You got it.
Energy is stored in the blood, in the bones, and in the organs.
Wherever there is a bit of tissue, we have the ability to store power in the form of a large branched polymer of glucose called glycogen. Each individual cell has the capacity to store at least a little of this material. Most of us store a surprising amount of power in our bodies. This is the power that keeps us going when we find ourselves benighted in the wilderness. This is the stuff that puts pop in the poop.