No idea. Too much speculation involved. Given that he has a really disformed body and a really ugly personality I agree its probably something that has not much to do with love.The problem here is (ignoring that she's out of his league), he clearly lacks the ability to love other because he doesn't love himself enough to treat his body with respect.
And especially at his size, I doubt that sex is an option.
So really, what are they both getting out of this relationship?
I mean she is not ugly so he probably said deal.