On my first fast it was about that, but if I pushed it too much on later fasts I noticed I regained more. Plus of course it depends on what and how much you eat.
I think it's all to do with what are referred to as artificially high metabolic set points, I think your body needs time and energy to make changes. It's as if all your muscles and bones are finely tuned to be the correct size and strength, and need time and energy from food in between fasts to readjust. That's how I view it.