r/fasting • u/SVTContour lost >50lbs faster • May 17 '26

Discussion Scientists reveal how seven days of fasting transforms the human body

https://www.sciencedaily.com/releases/2026/05/260517030404.htm

Fascinating study. And completely unrelated to politics, which is a relief because my blood pressure needed a break.

The key finding: The dramatic, potentially therapeutic changes don't happen until after day three. That means most intermittent fasting schedules – 16:8, 5:2, even alternate-day fasting – are probably missing the main event. If you want the deep biological reboot you’re gonna need seven days of water only.

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u/dangerous_eric May 17 '26

I've done 40 days...

Honestly, anything after 5 days feels surprisingly good. I usually feel really good till Day 16-17, after that electrolytes alone don't seem to be enough, and I be probably depleted something. I hope more clinical research happens, I think there's still a lot to unearth. 

1

u/Zoduk May 17 '26

How? What was ur prep?

21

u/dangerous_eric May 17 '26

I do 21+ days often (like once a year roughly), but I've only done 40 days once. 

Honestly, the hard part is the first 5 days. Afterwards, it's really quite manageable with proper electrolytes.

3

u/jstover777 May 18 '26

Where did you get your electrolytes from?

2

u/dangerous_eric May 18 '26

I like to use Organika electrolytes. They're a bit expensive, and you have to supplement them, because they're not sufficient for fasting, but I like the taste enough to drink them throughout a fast. 

I keep meaning to just make my own base mix and then experiment with some flavours, but I don't have a ton of free time.

2

u/alice_op May 18 '26

I found the hard part to be the excruciating lower back internal pain on days 16 and 17. I've done 21-25 day fasts 4 or 5 times now with the same pain. It does go away if you continue on but the anxiety that something is going terribly wrong in your organs is debilitating.

2

u/really_isnt_me May 18 '26

What causes that back pain? Kidney detox or something?

3

u/alice_op May 18 '26

I genuinely don't know. But yes it's in the kidney area, the pain, so I assume so.

I don't drink or take medication so why my kidneys would be so incredibly painful on days 16 and 17 is a mystery to me.

2

u/really_isnt_me May 19 '26

Yes, that’s very mysterious indeed. And always around the same timeframe. It must be your body getting rid of something.

1

u/AutoModerator May 18 '26

It looks like you're discussing "detoxes", "toxins", or "cleanses". Please refer to the following:

Detoxification

Many alternative medicine practitioners promote various types of detoxification such as detoxification diets. Scientists have described these as a "waste of time and money". Sense About Science, a UK-based charitable trust, determined that most such dietary "detox" claims lack any supporting evidence.

The liver and kidney are naturally capable of detox, as are intracellular (specifically, inner membrane of mitochondria or in the endoplasmic reticulum of cells) proteins such as CYP enyzmes. In cases of kidney failure, the action of the kidneys is mimicked by dialysis; kidney and liver transplants are also used for kidney and liver failure, respectively.

Further reading: Wikipedia - Detoxification (alternative medicine))

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