Forget just taking the stairs, there's a lot more you can do at work to help burn calories during this holiday season.
First off, if you have a couch at your workplace that's a good piece of furniture to work your triceps on. Triceps extensions are a pretty basic workout, but do several reps of these and you'll feel a tight burn.
Another thing everyone has in an office setting is a chair. Try balancing on the chair while swirling your leg around counter clockwise. You should try this for about three and a half minutes per leg.
Finally a nice multiple muscle workout is the 'workplace plank.' This challenges the lower abdominal and back muscles. Push forward with your calves, do a push up and back up. Or you can stay down while keeping your back straight to feel the burn. It's recommended doing this seven minutes daily.
Here are many more workouts you can do to help burn calories at work: http://exercisingatwork.net/exercisingatworkguide/