nothingbetter
I am on day 10 of my water fast, and my weight on the scale was stagnant for three days.
The thing you have to remember is that no matter what, you are still consuming energy. That energy has to come from somewhere. If you're not eating anything, no fruit juice, no "calorie free" soda or gum (i.e. approx 5 calories per serving - there is no such thing as a calorie free food only a calorie free label) then the only place it can come from is your body. And if you're fasting for more than a few days, its coming primarily from your adipose tissue.
Much of the weight you lose on a fast is water weight, but you also lose a lot of fat. Think of times when there is no change on the scale as solidifying the number on the scale - turning it from representing mere water loss which will be replaced immediately, to fat loss which will not be.