Everyone might as well eat as much as they want on Thanksgiving. Your body can only absorb so many calories in a short period, my guess is 5-6,000 max. Sure, you can gain 5-6 pounds from the food, carbs, sodium and water, but it will all pass through in a few days. Worst case scenario you'd add 2 pounds of fat (7,200 calories) and even that is doubtful, most is water weight.