I don't want to hijack this thread, but my perspective is that ~98% of morbidly obese people are that way through entirely their own fault. Genes have some play, but they're not the whole story. Add in that the wife was a normal healthy weight on her wedding day, I'm firmly in the camp that her size is entirely her own doing, and her not getting back to a healthy weight is a choice that she is making.
Not saying losing weight is easy, but she's not even trying. Her husband being celibate as a result doesn't even phase her.
Then you take the point (mostly overlooked) that she holds him REJECTING the advances of someone against him. This is a classic person who refuses to control them-self and insists on trying to control everyone else.
So, yeah, in his shoes, I'd leave. Or have extramarital affairs. No way I'd stand pat and be celibate for someone who can't be bothered to care about her husband to even try and change her habits.
ETA: Anyways, my comments are about my snap judgement of her, not all fat people everywhere. She sounds like a piece of work.