People change after marriage. Whether it is the natural result of aging, or something happens, they change. If they are physical changes, those are to be expected of human bodies.
I have to say, if my ex had gotten fat instead of becoming mean, we'd still be together. People who complain about a fat spouse can just STFU, if that spouse is still treating them like a human being. I only wish my problems had been so minor.
I am fortunate enough to have a kind, gentle husband now. If I had to choose between him becoming physically unattractive (without him suffering) and becoming a raging asshole, I would pick the former, and still sleep with him, because I love him.
Edit: I see some who are coming from "My Fat Spouse". I'd like to request that Meowser call the Waaaaaaaaaaahmbulance for y'all. I'm sorry that you're such shallow, selfish people that you actually seem to believe that your spouses gained weight just to spite you.