Glycogen

Physical activity before fasting can shorten glycogen depletion by reducing liver and muscle glycogen. The body has limited glycogen storage and much larger fat storage capacity. A high-carbohydrate final meal starts fasting with liver glycogen topped up, while a low-carbohydrate meal can allow earlier fat mobilization and ketone production. Glycogen is less space-efficient because it binds water and has lower caloric density than triglycerides. The article argues that carbohydrate storage is the body's smallest and most limited energy reserve. A lean person still carries roughly 100,000 calories stored as body fat. The article estimates that storing a lean person's total energy reserves as glycogen would require about 630 pounds of tissue. The article claims maximum glycogen stores are about 2,000 calories across liver and muscle. The article gives total glycogen capacity as approximately 1,500 kcal, with higher capacity in carbohydrate-loading athletes. When glycogen storage is full, excess carbohydrate is converted into fat for long-term storage. The article rejects the claim that glycogen binds exactly two water molecules per glycogen molecule. Once glycogen stores are full, a…