It's not uncommon for obese people to drop 5-10 lbs of water weight the first day or two, then it slows down to 1-2 lbs a day. The fatter you are the more water weight you have.
Fasting/dieting can stir up gout, because it creates an increase of some kind of acid in the blood...I forgot...you can google fasting and gout, there is a reason. it caused an episode of gout in my toe once years ago.