What you're really losing is water, glycogen, and muscle. This brings us to the scale's sneakiest attribute. It doesn't just weigh fat. It weighs muscle, bone, water, internal organs and all. Losing muscle is nothing to celebrate.
Muscle is a metabolically active tissue.
The more muscle you have the more calories your body burns, even when you're just sitting around. That's one reason why a fit, active person is able to eat considerably more food than the dieter who is unwittingly destroying muscle tissue. One pound of fat is like a big fluffy, lumpy bunch of feathers, and one pound of muscle is small and valuable like a piece of gold. Obviously, you want to lose the dumpy, bulky feathers and keep the sleek beautiful gold. The problem with the scale is that it doesn't differentiate between the two.