Think of glycogen as a refrigerator. It’s designed for short-term storage of food; it’s very easy to move food in and out, but the storage space is limited. Body fat, on the other hand, is more like a basement freezer. It’s designed for long-term storage and is more difficult to access, but it has much greater capacity. Plus, you can always add more freezers to the basement if you need them. When we buy groceries, we store food in the refrigerator first, and then when the fridge is full, we store the excess food in the freezer—that is, we store food energy first
