You know...I wonder what would happen if someone joined in, and turned the dial up to 11. "It's so good to hear someone speaking out against the standard message that society gives these days, and you're right.  There's absolutely nothing wrong with gaining weight, as much as you might happen to gain.  If you decide you feel best at 600 pounds, that's your decision, and you should be free to enjoy life that way." The key would be not sounding at all sarcastic, and seeing if they choke on their own logic when it's echo'd back to them.