I actually TRIED something like the Atkins diet before I knew about IBS triggers--I thought I would die from the pain. After reading Heather's book and this website, I realized why that happened. So I've tried telling my Atkinized friends this story and they STILL don't get it. Now I usually just tell people I'm on a "special diet, ordered by my doctor," or that I have severe food allergies.
One thing I've found: When people have not experienced chronic pain, food sensitivities, etc., they are just not very sympathetic. That's why it's so helpful to chat with people who've been there!!