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.
Excess post-exercise oxygen consumption In recovery, oxygen (EPOC) is used in the processes that restore the body to a resting state and adapt it to the exercise just performed. These include: hormone balancing, replenishment of fuel stores, cellular repair, innervation and anabolism. Post-exercise oxygen consumption replenishes the phosphagen system. New ATP is synthesized and some of this ATP donates phosphate groups to creatine until ATP and creatine levels are back to resting state levels again. Another use of EPOC is to fuel the bodyâ€™s increased metabolism from the increase in body temperature which occurs during exercise.[2]