The funniest one I've had to date is: "You know...I heard someone's kidneys exploded from following a low carb diet."

The second best so far was in response to my answering the question of how much more I want to lose: "OMG! There won't be anything left of you if you lose that much!" LOL...there will still be plenty of me left when I get to my goal weight, I assure you...just about half as much of me as there was before.