where does body get energy from when fasting
Starvation response Starvation mode is a state in which the body responds to prolonged periods of low energy intake. During short periods of energy abstinence, the human body burns primarily free fatty acids from body fat stores, along with small amounts of muscle tissue to provide required glucose for the brain. After prolonged periods of starvation the body has depleted its body fat and begins to burn primarily lean tissue and muscle as a fuel source.
Anaerobic glycolysis Anaerobic glycolysis is the transformation of glucose to lactate when limited amounts of oxygen (O2) are available. Anaerobic glycolysis is only an effective means of energy production during short, intense exercise, providing energy for a period ranging from 10 seconds to 2 minutes. The anaerobic glycolysis (lactic acid) system is dominant from about 10â€“30 seconds during a maximal effort. It replenishes very quickly over this period and produces 2 ATP molecules per glucose molecule or about 5% of glucose's energy potential (38 ATP molecules). The speed at which ATP is produced is about 100 times that of oxidative phosphorylation.