Body state after enlightenment

I've heard (not from Buddhist texts) that after enlightenment the investment in the body dwindles becomes delicate and less resistant to disease ,and that the body needs to be prepared first.So what Buddha had went through before Nirvana was important.Or what the yogis do in kryia yoga . Examples of Ranamnakrishna and Maharishi Raman dying of cancer . There is even claim that some might die right after nirvana. Another claim is that there is no longer unconscious sleep,One is always awake /sleeps less . Example of krishnamurti not sleeping well and having migraines. If there is any such thing what do Buddhist texts say about the state of the body after nirvana ?