Kate also recently answered this question, and she isn't even an advice columnist. She was just fed up with the way people who are advice columnists have historically bungled it.
Dear Not Attracted to Your Spouse Anymore (writes Kate):
Get over it or get a fucking divorce. And I truly mean you should consider both options seriously. If you believe it is actually possible for you to get over it by which I mean, you find a way to reframe the way you look at your fat partner, find him attractive again, and go back to whatever you both agree is a normal sex life then by all means, work on that (provided everything else in the marriage is good and worth saving, which it probably isn't if you're not even a little bit attracted to him anymore).
If, however, you're so hung up on your partner's weight that you can't even conceive of being attracted to him anymore? Get a fucking divorce already. (Writes Kate, who is not an advice columnist.)
Hear hear, say I, who am.