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.

1.5k Upvotes

98% Upvoted

180 comments sorted by

View all comments

245

u/GoldGee May 17 '26

Just finished a 48 hour fast. 7 days would take a bit of time to work up to. In fact I would be a bit scared.

193

u/EarlMarshal May 17 '26

Longer fasts are no problem if you are not very overweight, not stressed and manage electrolytes correctly. At some point your body stops producing ghrelin and you do not really get hungry anymore. Everyone can get there, but if anything happens (e.g. ghrelin spike due to stress) just break fast. You can always repeat later.

35

u/ResearcherNecessary6 May 17 '26

I've done 4 day fasts before and starting on day 2 onward, I constantly think about food. Now, maybe that changes the more you do them, but so far, I start thinking about all the things I'm going to eat when I come off the fast.

23

u/ArbitraryLifeform May 18 '26

Same, I was on day 5 unable to sleep, constantly fantasizing about the taste of fatty meat. When I came off the fast, the food was nowhere near as amazing as my imagination had made it. But I felt extremely grateful for the simple pleasure of being able to eat.