I'm in a similar boat at work...everyone already knows I don't want the cookies and no one bothers to ask if I want to order chinese for lunch. It makes saying no a lot easier. If I do decide to eat something, they all look shocked and I just tell them that I watch my diet enough, one thing won't kill me. But I also know I'm an all-or-nothing eater, so just staying away is the best thing for me. When we have company catered lunches, I still bring my own. Yes, I too feel odd sneaking in my healthy lunch while everyone eats burgers, potato salad, and cupcakes, but I always feel full and satisfied and better abount myself.
Way to go for sticking to the plan!