You body stores about 1 pound of glycogen (a quickly available starch energy source) in the muscles and the liver. With it is about 5 pounds of water. When you eat a low carb diet, the first thing your body does is burn that off. That, plus dehydration, means you can expect to lose about 6-8 pounds in a few days. I can and have done that many times. And then I can gain it back in two more days with a couple of big plates of pasta. Competitive athlethes like wrestlers who need to make weight can routinely cut and gain a temporary 15-20 pounds in less than a day.
In other words, sorry if you don't believe me, but much of what you lost was water.
I know all this. But when the weight stays off, and you in fact continue to lose weight in the following weeks, then it is not water loss. A lot of muscle, yeah.
In other words, sorry if you don't believe me, but much of what you lost was water.