No, nuclear fission does not occur naturally in the human body. Nuclear fission is a process in which the nucleus of an atom is split into two smaller nuclei, releasing a significant amount of energy. This process typically requires highly unstable and heavy isotopes, such as uranium-235 or plutonium-239, and specific conditions to initiate the chain reaction.
The atoms and minerals found in the human body, such as carbon, hydrogen, oxygen, and calcium, do not possess the necessary properties for spontaneous nuclear fission to occur. The elements present in our bodies generally have stable nuclei and do not undergo nuclear reactions on their own.
The energy that sustains life in the human body comes from the chemical reactions that take place during metabolism, not from nuclear fission.