I have a client who says she needs the month of December off from exercising and eating right. WOW!!! So you want to eat as much as you can and not exercise for a whole month and then what? Come January, make up for it? You can't skip workouts for a few weeks (or the whole month of December!) and think you can make it up with one really long workout session or a good long run. The body only regularly turns to fat burning when it gets a routine blend of cardio and muscle work, as well as a daily healthy diet.
Why would you want to start the New Year weighing more, or being in a less healthy state? Consistency is the real answer!