It is known that a person can go without food for a long time, while maintaining physical and mental activity. How is this possible?

In the case of prolonged starvation, the body rebuilds its metabolism in such a way that plastic metabolism temporarily stops, and energy becomes predominant. Energy for the work of the brain and other organ systems is provided by the oxidative breakdown of organic substances contained in cells, especially in adipose tissue. A person loses weight a lot, sacrificing part of his cells to maintain the vitality of the body.