How do you combine eating at a friend’s house with following your protocole ? (Overeating question)

I’m listening to the overeating workshop and I have started the work this Monday – I have a protocol that I follow but I wonder what to do when I’m invited for lunch at someone’s place (not eating out at the restaurant)
In France, flour is a BIG thing, I don’t mind skipping bread or desert but what about if the main meal has some ( pizza, quiche, etc …)
I can’t picture myself not eating anything when someone has cooked for me and I can’t see myself saying in advance “thanks, but can you cook something without flour or sugar ?”

Can you put me in the right direction to come up with a plan or an idea to handle these situations ?

Thanks a lot