Dry Fasting

I see people online claiming massive physical and mental benefits from this practice. It’s basically not drinking both water or food at all for prolonged periods of time. It sounds like a recipe for dehydration to me but I wanted your thoughts on it. Fasting seems to be becoming more and more popular online, which in turn is also giving more light to these more niche practices. I’ve seen people routinely claim to be going a week or more with zero food and water and then saying how much better they feel afterwards, how much more mentally aware they are and basically going around promoting this practice to everyone. There are even some influencers on instagram claiming to have gone 20 days or more with zero food and water and claiming massive benefits. A lot of these people also say you should not even touch water, ie bathe, shower, brush teeth, do the dishes or anything of that sort for the duration of the fast because apparently “your skin can absorb the water and hydrate you through it”.

I’m personally having a hard time believing any of these, it seems to me that these people are either lying to seem “tough” (common online behavior) or just quacks. From what I know the human body can survive a few days to max around a week or maybe two without water, but I see people routinely claiming going close to a month with no water for this “fast”, some guy even wrote a book about it and claimed to have gone 21 days with no food or water.

  1. Does this “dry fasting” thing have any evidence to back up the claimed benefits at all? The benefit claims are usually the same as intermittent fasting or water fasting but x5, “autophagy on steroids” they say. If these people are willing to suffer chronic dehydration for a bunch of benefits, I would at least hope there is some sort of an evidence base.
  2. How long can the human body actually survive without water? Should I give any credence at all to these claims of “20 day dry fasts”?
  3. I got curious about this one because people in that space seem to claim this a lot. Can your skin actually absorb water to hydrate you? As in do you actually get hydrated when you take a shower, do the dishes, go for a swim etc. or is drinking the only actual source of hydration? These dry fasters claim you do which is why many suggest to completely avoid touching water at all for these week long fasts.

Hey Rupert,

Thanks for the post. Do your questions:

  1. No, there are no unique health or performance benefits to fasting. Autophagy tracks with energy balance (among other things) and there’s no difference in autophagy rates between fasting and the same energy deficit over the same period of time. Autophagy is not always good either.
  2. Some case reports of up to 21 days I’ve seen. I’m sure there’s a range. No, I would not take anyone seriously who suggests fluid fasts are healthy.
  3. People in this space are VERY dumb. I cannot stress this enough. People just make stuff up to explain the world to themselves, but some do a worse job than others. The skin is water tight for the most part, which is why you don’t leak out your insides (we’re mostly water) into the environment. Percutaneous water absorption is not a viable strategy for maintaining hydration and these people are almost assuredly dehydrated. Week long fasts in young, healthy people are not particularly impressive to me either.

-Jordan

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That’s interesting. People seem to overrate it a lot claiming everything from anti aging benefits to disease reversal. In what circumstances is autophagy a bad thing?

Do older people dehydrate faster?

Wasting diseases, infections, when receiving various cancer treatments we may want to inhibit it, etc.

To be clear, I do not know of educated individuals talking about autophagy as a lifestyle target. It’s only grifters.

Not really, but they may be more sensitive to the effects of it.

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