Here's why:

* Glycogen is a complex carbohydrate made up of many glucose molecules linked together. It's primarily stored in the liver and muscles.

* When you eat, your body breaks down carbohydrates into glucose. Excess glucose is then converted into glycogen for later use.

* When your body needs energy, glycogen is broken down back into glucose, providing fuel for your cells.

While fat is also an important energy storage source, it's not the primary one the body uses. Fat is primarily used for long-term energy storage and insulation.