What is the energy of the human body?

The energy directly used by human life activities is ATP, which is produced by breathing.

When there is no external energy supplement, the human body consumes the sugar in muscles first, and then consumes the sugar stored in the liver. After the sugar in the liver is consumed, it will consume fat (fat is actually a storage form of extra energy at ordinary times). When the fat is consumed, it will consume protein. When the human body began to consume protein, it was on the verge of death.