We're told throughout the movie that "the same matter cannot occupy the same space".
Yet, even after a few months it's very unlikely that there are many of the same atoms in your body that were there originally. You're constantly breathing out carbon dioxide, and most of the carbon in your body is cycled out for new carbon atoms very quickly. Even the calcium and phosphorus in your bones would be constantly replenished, as both are used in normal metabolism (not that anyone has bones on the outside of their bodies).
So what gives?
Here is a Youtube clip of the to-be-avoided event.
Best picture I could find: