Based on statistical peculiarities of the existence of two-leveled thermodynamic systems, it was shown that the probability of existence for warm-blooded organisms is determined by body temperature, energy of metabolism, and thermodynamic potentials of critical increase and decrease in the body temperature. It was established that the dynamics of human death rate from the birth to extreme old age is conditioned by age-related changes in the energy of metabolism. It was shown that maintenance of the metabolic level in aging is very important for the life prolongation.