How much you want to loose is up to you. I've lost 10 lbs in 7 days on a water fast. You could loose much more, but it all depends on what you choose to do. Stuff yourself on Thanksgiving? You're going to gain weight. It is much easier to control what you eat than to try to exercise it off. If you are going celebrate Thanksgiving, eat a lot of vegetables at the beginning of dinner and go easy on the meats and desserts. Until Thanksgiving, start eating primarily fruits and vegetables, count every calories (1800 cals/per day for men, 1500 cals for women) drink water instead of eating, and remove temptations from around the house. There are plenty of other tips but it all depends on you level of commitment. Also realize if you do fast, you will gain some of it back if you don't have extensive after-fast care. Good luck.