I wouldn't worry about being rude, I'd bring something and just say that you're on a special diet with all kinds of restrictions. Make note of telling your host/hostess that you didnt' want to burden them....you knew if they were told about your restrictions they'd go out of their way to make sure you had something you could eat....but you figured it was easier on them if you just brought your own choices.

If you dont' want to mention LC or Atkins, and a lot of us dont' because of the "discussion" that might induce, don't. Just say it's a special restriction that you have to follow for X number of days and dont' want to have to start all over again. Use anything as an excuse.....I usually blame allergies or stomach trouble.

Before you go, make sure you eat, so you wont' be starving. Maybe pack a low-carb bar too.

Another thing you could do is bring a couple of LC appetizers....stuffed mushrooms, something like that. And just say they're new recepies you tried and wanted to share with everyone. If you can bring 2 or 3 items, that should do it!

Good luck!
Cindy