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Comment by mrfusion | Hacker News Reader

I’ve been wondering if water is stored in fat cells? Does the body burn fat for the water content when you get thirsty?

https://en.wikipedia.org/wiki/Metabolic_water

> Animal metabolism produces about 110 grams of water per 100 grams of fat, 42 grams of water per 100 g of protein and 60 grams of water per 100 g of carbohydrate.

The amounts listed is a bit puzzling. For every gram of glycogen stored (stored carbohydrates) 2-3 grams of water is needed, so naively one would thing the number should be much higher for carbohydrate.

Don't quote me but what I remember is that water is roughly stored with "sugar" in short term storage (liver, muscles) at a 3:1 ratio and in long term storage (fat cells) at a 1:1 ratio.

My guess is that while it may sound good in theory it would in fact be counterproductive, especially considering that we evolved as a tropical animal: need more water -> burn more fat –> generate more heat -> need to cool down -> sweat more -> need more water...

You generate water through metabolism.

Of course, but metabolism also generates heat, and heat needs to be dealt with by evaporating water. Consider that the only human tissue that increases its metabolic rate just for the sake of it is brown adipose tissue[0], and its purpose is to generate body heat. On the other hand, compounds that can significantly increase base metabolism (and thus generate more water) such as 2,4-dinitrophenol[1] are dangerous because they can easily result in lethally high body temperature. That's why increasing metabolism with the sole purpose of generating water would be self-defeating.

[0]: https://en.wikipedia.org/wiki/Brown_adipose_tissue

[1]: https://en.wikipedia.org/wiki/2,4-Dinitrophenol

On a high fat ketogenic diet, my thirst is satisfied on ~500ml of water a day. I drink much more when running on glucose, if it's really hot or I exercise intensely.

High fat, or actually ketogenic?

Just curious, really. I'm not aware of any serious downsides to ketogenic diets, except I suppose for the smell, but it doesn't take much glucose or starch at all before ketone bodies are no longer needed.

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