Carmen

We all die at some point, but cancer of the tongue is an especially gruesome and painful way to die if left untreated. If your co-worker persists in such remarks, you can always ask nicely;
Oh, really? You would prefer to have a tumor block your throat and your airways slowly while it spreads until it bursts through your cheeks just to avoid temporary suffering?
Optional reply depending upon how corpulent your co-worker is:
"Oh really? It wouldn't do you any harm to lose some weight !"
But then I am cantankerous and have actually used such comebacks after I returned to work and heard the same thing.
It did put an end to their comments though.