It just screams that he settled for her all those years ago when she was fat but he could deal with it over the alternative of being alone. Notice he mentioned that it wasn't an issue before, so obviously now she's expanded to something even he can't handle. And of course he won't just up and say that she's a fat cow and he doesn't want to fuck her anymore. He put the weight issue at the very end, as if it was an afterthought and wasn't really the reason he can't stand her. Either he's deeply in denial about the whole issue, and is just trying to find another excuse, or he's so beta he can't even face the issue head on and just hopes someone will suggest a solution that doesn't involve him breaking up or actually improving his life.