Salt has no calories but makes you fat. It causes people to retain water. Not only does the water fast cause people to lose water weight but a juice diet or any diet with no salt causes them to lose water weight. I have a big section about this on
Losing Weight.
If someone goes on a diet with no salt, they will lose all that water weight just like on a fast. Salt is not a food. A quarter pounder burger is 4 ounces. You could eat lots of them and not die. If you consume 4 ounces of salt at one time, then you die.
Salt causes water not to work. If you drink sea water on a raft in the ocean, you get more dehydrated. Salt is anti-water. Your body decides to add or subtract water to your body by the concentration of sodium in it. It is normal to retain lots of excess water weight when consuming a fair amount of salt.
On the site above you can read how even the AMA wants to make salt a restricted substance. Of course they (MDs) make their money from people getting heart attacks and strokes, but with too many, there is not enough money in the country to pay for it.
Dr Shelton says that on a fast someone can lose up to 80,000 mg of sodium in a single day. Urine and sweat are very salty since the body is desperate to get rid of it. But people who do not consume salt do not have salty sweat and urine.