Can you get up and walk or exercise or do something?
For me sometimes what helps is getting out of the house or the office or whatever environment I'm in, and into a different one. If I can, and I'm really feeling a lack of control coming on, I go to the gym. There's something about working out that gives me my control back ... once I've put in the effort, I don't want to "waste" it by eating stuff that's bad for me.
If you can't do that, then do something that keeps your hands busy. Clean - let the smell of cleaners take the thought of cheesecake right out of your head. Or type something. Or knit something.
Or anything that will keep you busy and not thinking about food.
Hang in there - it's even harder at this time of year. If nothign else, know you're not alone! )