How does the body primarily store energy?

The body primarily stores energy in the form of glycogen, which is a polysaccharide that serves as a form of energy reserve. Glycogen is predominantly found in the liver and muscles. When the body requires energy, glycogen can be quickly broken down into glucose and utilized during various physiological processes, especially during physical activity.

While fat serves as a long-term energy storage molecule and is highly energy-dense, glycogen is more readily accessible for immediate energy needs. The liver stores glycogen for maintaining blood glucose levels between meals or during exertion, whereas muscle glycogen is used directly by the muscles for energy during exercise.

In contrast, protein is not a primary energy storage form; it is mainly used for building and repairing tissues, and only in conditions of prolonged fasting or intense exercise does the body begin to utilize protein for energy. Calories are a measure of energy but do not represent a form of energy storage. Therefore, glycogen is the most efficient way for the body to store readily accessible energy for short-term use.