My wife's so fat we were sunbathing on the beach today and the Lifeguard came over and said to her. "Excuse me Miss, could you move, the tide's waiting to come in".
I may not know all the details of your relationship, but do you think you should make fun of your wife's body?
Well, I'm a man who has a wife with a fat ass, so I deserve to be able to joke about her.
You're not supposed to talk about your overweight wife like this. You're mocking her by comparing her with a tide. It's insensitive to use her as a joke.