Question

Why does a completely inactive person consume energy even when asleep

Answer 1

While sleeping our voluntary function are not working but our involuntary functions like beating of heart, digestion,etc are still working.These functions need energy to work properly and so energy is consumed even when we are asleep.

Answer 2

When in the state of rest the body will still continue using energy for the working of the organs and parts which are not in the willpower or control throughout the body, that is, the involuntary parts consume energy and need a constant supply of ATP and glucose molecules. Such as, heart, lungs, stomach, etc. all of them take a small part of involvement in making even the inactive or a person in the rest phase seem out of energy. So, a high diet is often needed for the person in rest, as, to provide them the adequate amount of energy used by the involuntary organs (contributing to heart ailments and major risk for obesity). Therefore, be active and exercise a lot :)