Why people say that the weight lost during water fasting is mostly water?


I have looked at answers on the internet, but I still don’t get why if someone is exclusively **drinking water** for a period of time, the weight lost is **also water**… which does not provide energy nor is scarce for the body during that time.

Is this real? Why does or bodies behave that way?

In: 0

The body has two energy sources: glycogen (sugar) and triglycerides (fat). The body can store any amount of fat, in fact it will grow more space if you give it reason to. Sugar storage, however, is limited to skeletal muscle and the liver. The body prefers to use sugar as fuel first and while fasting will do so. The thing about using sugar as fuel is that it takes water to burn it (or store it, I forget) so the body also carries water for that purpose. Once you’ve used up your sugar reserves, the water is used up with it.

Your body still needs water to function, so during water fasting you drink water, but it’s for other bodily functions.

First, if you are not consuming calories, your body is going to use stored energy. One of those energy stores is glycogen, which is stored in the liver and muscles. Glycogen is easily converted into glucose which your body can use for energy. Glycogen is stored with water in a 1:4 ratio. That is, every molecule of glycogen takes four molecules of water. So, as you use glycogen, there is excess water released.

Second, water is a byproduct of cellular metabolism, so if you aren’t consuming calories through food, but expending them metabolically, then you are going to be producing some excess water.

Third, sodium also causes you to retain water. If you start drinking a lot more water than normal, you are going to dilute the amount of sodium in your body, which will allow you to release a lot more water since there is no sodium to retain the water.