In humans the majority of glycogen is stored in skeletal muscles (∼500 g) and the liver (∼100 g). Glycogen is accumulated in the liver primarily during the postprandial period and in the skeletal muscle predominantly after exercise. Muscle glycogen decreases by ~30% after roughly 72 hours of fasting at rest.
The reduced glycogen stores in skeletal muscles after exercise allow carbohydrates to be stored as muscle glycogen and prevents glucose from being channeled to de novo lipid synthesis, which over time can cause ectopic fat accumulation and insulin resistance. The reduction of skeletal muscle glycogen after exercise allows a healthy storage of carbohydrates after meals and prevents development of type 2 diabetes.