Assuming you do not gorge yourself every day like its Thanksgiving day, you shouldn't actually put on much fat weight. You may actually lose fat as your body is readjusting to 'normal' stressors.
Glancing at your profile pics, It looks like you have decent muscle mass in structure of the muscle, thus any loss for an extended vacation will be minor, and most likely not really noticeable on observation.
I know several guys who have taken off a whole month and a little more, starting with Thanksgiving, ending New Years. Inevitably what happens is minor chances in muscle mass and little to no increase in body fat percentage. They do, however, see great gain when they go back to the gym, their muscles act and react as if its the first time they lifted.
One of the most sensible (from a medical point of view) systems I have seen breaks down the year into 4 'seasons', every other season is dedicated to either endurance/definition or mass building. Between each season is a two week break with little to no cardio. Thus the first 'season' they are hitting heavy weights, low reps for 11 weeks, taking 2 weeks off, then hitting the lower weight higher reps and sets for 11 weeks, taking off 2 weeks, around and around.
This not only provides your body with a decent rest period for full recovery, it also gives you sufficient changes in the routine to prevent plateauing or becoming stale.
The reason why this is medically sound is because it gives the body an extended period of time to actually recover from the constant 'injury' to the muscles. The workout 'shreds' muscle fibers/tissues, breaks it down, the following 2 day break is where the real muscle growth takes place as the body repairs the tissue, stronger, more dense and tougher in and effort to prevent future 'injury'. while a good deal of healing does take place the first 48 hours, the tissues do not completely heal before the next workout. Thus an extended break allows for complete healing.
All tissues in the human body repair stronger, denser, thicker and more resistant to injury after injury.
"Vacations" also help to break plateaus. If you reach the point where you are not seeing gains in weight added to the bar, you can either switch up the type of exercise (with minimal gains) or take a break, tricking the body into thinking that the stress and strain are over with, thus it starts reverting back to 'normal' thus the next course in stress it will react like its being presented with the resistance/strain like new.