Adapted from a recent online discussion:
My fiancee was HOT when I first met her. She was still HOT when I proposed. I don't love her for her body, but it did have a lot to do with our great sex life.
Since we got engaged, she has gained 45 pounds. She swears it is "contentment weight" and that she isn't depressed or hiding. She has changed wedding dresses three times because of the weight gain. I am plainly unattracted to her right now and a little resentful that she hasn't done more to take care of herself.
I want her to lose the weight, or our upcoming marriage is going to suffer sexually and emotionally. I want her to be healthy, too, but she and I both know that's not the main reason for my concern here. Is there a way to bring this up without being the pig of all pigs?
-- Honey, You Do Look Fat
I think you're going to be called something bad no matter what, and, for the record, it will be unfair. That's because when you do speak up (you have to), you'll deserve points for honesty and for facing an issue that has to be faced before you get married. You can't marry someone you no longer find attractive. It's unfair to both of you.
Here's the thing. Weight isn't just about looks, as you said, and it isn't just about health, as you said. It's also about a general . . . what's the word, trust? between two people. When she put on so much weight so quickly, she basically announced to you, "I pretended to be someone I wasn't for the sole purpose of landing a mate."
That really stinks. And it stinks even more when it's a function of weight, because if she had pretended to, say, enjoy your hobbies (as so many people pretend to do when they're dating), or to like your family and friends (as so many people pretend to do when they're dating), or to want kids when she privately didn't, then you'd have everyone's sympathy as the victim of her bait-and-switch. But when the bait-and-switch involves physical appearance, you're the one who gets called the pig.
But the essence is still that she thought it okay to maintain her appearance only as long as it took for her to get engaged. And so it doesn't matter what trait she was misrepresenting in herself -- it's still acting in bad faith.