At holiday parties, and the holidays in general, the rule is that you're supposed to eat as much as you possibly can, and then continue eating for 10 more minutes. I once heard that your stomach doesn't tell your brain you're full until 20 minutes after it's reached capacity, and if that's true, then you've stuffed about an extra 30 minutes of food on top of what you should have eaten. I have never met anyone who does not operate based on these principles, and I've found that almost all of my friends are fit. I therefore deduce that this is acceptable behavior, and you, therefore can assume so as well. Happy holidays.