Forms of Fat as Fuel

Fatty acids are the primary form of fuel from fat. They are stored in fat and muscle tissue as triglycerides. The aerobic system uses fat and glycogen as fuel for ATP resynthesis. The system creates a large amount of ATP through chemical reactions in the mitochondria but without fatigue as an end product. The aerobic system is used during heavy or light activities. Fats and proteins, when used as fuel for ATP resynthesis, go through the Krebs cycle and the electron transport system.