Personally I feel that if my husband gained a lot of weight I'd still be sexually attracted to him but realise that maybe I'm the minority? Obviously I want my spouse to be healthy and not hit an early grave but if we are talking purely from a shallow looks perspective, I feel I would be extremely attracted to them regardless of weight gain because it's the person and personality that's attractive to me.
I have gained a little weight since we met 15 years ago. That's not even post kids weight since we have no kids yet. Not much weight has been gained but enough for it to be noticeable and he's told me he's unnattracted to me and that I need to lose my tummy.