The technique is known as ‘accept and amplify. It always works.
She : Oh you are getting fatter!
You : Oh yes I am getting bulky and yeah my plans are working out to become a ‘elephant in the room’!
- When you accept, you cut their chances of further insults.
- They can fight back by amplifying your insult (if you defend). Hence you have taken that opportunity from them too by amplifying yourself!