It is easy sometimes to blame genetics, some obesity gene perhaps. But even if this were true, we’ll still be referring to the machine. Genetics are predispositions. The body is designed as a closed system, physiologically speaking and unless acted upon by an outside or higher force it maintains its functions. It is designed to sustain its own survival. The psychological (self-ordinate command) is essential for this survival because the body also belongs to a self, one that can overfeed it, starve it or kill it as may be. It is also by material urges that you seek to acquire wealth and by self command, suppose what you consider a higher more fulfilling purpose that you choose to give it all away.
The hard core truth is that despite some obesity gene, you can starve yourself to death if you want, or perhaps if you feel you have an ulterior higher purpose like an anorexic might, to look thin and beautiful in the eyes of the communal.
