I lost 10% of my body weight without even realizing it by just cutting out rice and breads. But that is mostly water.
However as you lose fat, your body can replace the fat with water and your weight wont change. It then all of a sudden lose all that weight in a matter of hours. I have stayed at the same weight for 8-10 days and lose 15lb in a 24 hour window.
Thanks.
Srinath.