Could you explain what exactly “water weight” is when experts say you’ve lost water weight?

Question

Experts are always saying that when we first start dieting that it’s the water weight that’s lost meaning it’s not fat or muscle. Can you explain what this water weight is exactly and where does it come from?

What would be the approximate normal amount of “water weight” that’s lost in an average male of say 175lbs and 510″ and a woman of 167lbs and 5 6″

Is this “water weight” the weight that can fluctuate within a 24 x hour or 48 hour period?

In: Biology

Answer 1

In an early episode of *Star Trek: the Next Generation*, an alien lifeform made out of crystal refers to humans as “ugly bags of mostly water”. While its assessment of our looks may a matter of opinion, the part about being mostly water is true. On average, our bodies are about 60% water, though it can vary between 45 and 75%.

Having the right amount of water in our bodies is very important. Many of the chemical reactions and physical processes that power our cells only work properly at specific concentrations. Because of that, the body has evolved several ways to get rid of water: everyone thinks of urination, amd that’s important, but sweating and exhaling also play big roles.

There’s one more thing I need to discuss before we get to water weight: water is heavy. A cubic meter of the stuff weighs about a metric ton (roughly 2200 pounds). Obviously people aren’t *that* heavy, but over half of the weight of our bodies does come just from the water in it.

And now we can talk about water weight: the part of our bodies’ weight that comes from water alone. It’s very easy to gain: all you have to do is drink water, and most of it will be incorporated directly into your body (and you really have no choice in this, because if you stop drinking you die). It is also relatively easy to lose: the water vapor just in your breath causes you to lose about a kilogram a day.

Because of this, some diet and fitness experts say that to at least some extent, water weight doesn’t really count, or at least shouldn’t be considered the same as other forms of weight. It fluctuates too much: you can’t stop gaining it, and you can’t stop losing it. Consequently, small weight gains are losses are likely to come from this, and just as likely to vanish.