One thing I do is bring something similar to what others bring, put in the table and put a goofy smile on my face. I never eat anything at these event. I'll usually fill a glass with water or club soda and when asked if I've eaten I say, "I'll get to that in a moment."
The worst was meals brought in at work. Gut Bombs! People just got used to me bringing in "health food," what ever that is. (Oh, you eat so healthy. What, you don't? Why not?)