164 replies to this topic

[HaplogroupW]

 

feel kind of weak and in a sort of lackadaisical state of mind. I rode my bike around the city yesterday and down the Fairmount trail, for a good hour and a half or so. Same the day before. I rode my bike to work this morning and felt like I was in a daze and that it took a lot of effort to pedal.

 

Your experience is so different from mine I'm thinking my suggestions don't apply to you. Sorry if I led you astray.

 

Or maybe sthira is right and I underestimate the extent to which a gradual acclimation to fasting plays a role. I know I first did a few 24 hour fasts, then a few 2 day fasts, 3 day, and finally a 5 day fast. But I never experienced the difficulties you described. I felt great doing my usual cycling (fairly intense 20 to 40 mile rides) on the extended fasts. I was fairly low carb (but not ketogenic) for probably over a year leading up to my fasts.

 

 

 

 

Edited by HaplogroupW, 18 May 2017 - 12:49 AM.

[xEva]

Nate, there is a long thread on the Russian fasting forum, about what is hunger and how people experience it. Before I started to read it, I thought I came prepared, with understanding that there will be a variation. I was stunned by range of feelings, thoughts and sensations described, some familiar, many surprising. 

 

and I remember my first ever fast. On the second night I could not fall  asleep. The moment I closed the eyes, my brain bombarded me with vivid images of colorful and fragrant dishes, very beautifully served! Never saw anything of the sort before or since then. At dawn, I finally fell asleep and woke up late on my 3rd day, weak but no longer hungry. I lasted 11 days. 

 

but if it was so hard for you, you should definitely consider appetite suppressants. You mentioned acid, that's a good appetite suppressant in my experience. I suspect that's why fasting is addictive to some of us, because when ketosis kicks in in earnest (on day 4-5) that's very reminiscent of the good ole times when we danced the night away on raves or explored the stunning beauty of the world. I never felt hungry then and it was customary for my company to take those things like a communion, in a fasted state (short-term fast, just from previous night).  

 

There is no better state than when you have plenty of energy, both mental and physical, and you're perfectly content. You don't need food. That's how it always should be. You should try doing it within 2 weeks, 3 at most. You will be surprised. 

 

 

 

Edited by xEva, 18 May 2017 - 01:16 AM.

[Nate-2004]

I can't imagine that ketosis takes that long to kick in during a full fast. 5 days?? I thought it was more like 24 to 48 hours without food. Surely glycogen stores are depleted a lot sooner, where is the brain getting its energy if not ketones? Is there research showing this? Most of my googling says 24 to 48 and some people recommend a full water fast to force ketosis to kick in sooner as an entry into HFLC diet.

Edited by Nate-2004, 18 May 2017 - 01:56 PM.

[xEva]

You should read Cahill and Owen, circa 1970s, where they show that with the onset of ketosis the liver starts churning out ketones at a constant rate. In the meantime, skeletal muscles are "not allowed" to feed off them. It takes several days for the level of ketones to reach ~3mMol/L. This concentration is conducive for their en masse penetration into the brain. This often coincides with an unpleasant drop in plasma pH and corresponding nasty symptoms. Finally the brain switches to ketones, though by only ~1/3 of its requirements. This eases the demand for glucose (which liver has also been churning out at about a constant rate).  

 

You can track this moment, first by suddenly feeling quite wonderful, and second, by noting a rise in blood glucose level together with a drop in daily weight loss -- higher glucose is because less of it is now picked up by brain; and smaller daily weight loss is because less protein (and water with it) is lost due to gluconeogenesis. (ah? trully, I deserve a medal )

 

the best high is when blood ketones are at 4-5mmol/L. 3 is the minimum.

 

Judging by your mention of ketostix, I doubt you got even close to 2mmol/l.

 

 

Edited by xEva, 18 May 2017 - 07:20 PM.

[Nate-2004]

They really need a plethora additional research on fasting in humans. If I were a PhD I'd be doing it among other things. Us lowly plebes can't conduct studies or publish papers with any credibility unfortunately.

 

I take it the above is on mice?

Edited by Nate-2004, 18 May 2017 - 08:01 PM.

[sthira]

They really need a plethora additional research on fasting in humans.

Word.

It's reallly obscene isn't it, given that fasting studies could be done and done again, again, and carried out in a wide swath of the population, then replicated, replicated again, and repeated over and over and in a short time period. Unlike the other bullshit peddled to us -- bs that requires first cells in Petri dishes, then maybe c. elegans, haha, fame for break through pivotal studies, then maybe -- oh wow holy shit: mice(!) -- then years and languishing and more years, study after study, kick up your feet, famous researchers, produce meaningless study after publication after study (how about more mice studies), oh we hope y'all get precious tenure, don't die, in decades, spending taxpayer millions, tens of millions, the excuses, the hidden failures, the trumpeted promises, oh science, you're so fucked up.

Meanwhile, maybe art school can solve human aging problems. At least our thrown paint sticks to the canvas.

[Nate-2004]

I love you Sthira. 

 

I am currently just doing the intermittent fasting for now. I did well today and will likely do ok tomorrow. Just takes some adjusting as to how I fit other things in.

 

I'm still deciding on the 16/8 schedule right now. It needs to be closer to night time because I have a LOT of trouble sleeping if I'm hungry, but I can't eat too close to bed either because that kills sleep quality. Also it needs to fit into my lifestyle. I go out a lot even on weeknights, I'd like to be able to eat out without worrying about this. So it's looking like 13:00 to 21:00 for me.

 

Downside of that is that not only do I love a good creamer in my coffee but I take nootropic supps that are fat soluble, like bacopa for example. So I'd have to take those later which kind of defeats the purpose.  I might take green tea extract instead during the morning. Supposedly this promotes autophagy. 

 

As far as the extended fast thing goes, I'm leaning towards awaiting more research before I devote days out of my life to it. I'll do it every now and then but if I'm going to extend my youthspan at all, much less my lifespan, I'd like my life to be full of enjoyment, not discomfort and misery. 

 

They say you shouldn't dip in and out of ketogenic. If you could I'd do that, but it takes weeks to get into ketosis with that and you have bad breath on top of all that. Screw that I'm still single and dating. I need that good makeout breath.

[xEva]

They really need a plethora additional research on fasting in humans. If I were a PhD I'd be doing it among other things. Us lowly plebes can't conduct studies or publish papers with any credibility unfortunately.

 

I take it the above is on mice?

 

 

Nope! Cahill and Owen worked exclusively with humans. And no modern ethics committee (which did not exist at the time) would approve now what they did then, which was the following:

 

On various days of a fast, they intubated fasting humans (who were mostly obese volunteers locked up in a metabolic ward for weeks on end) and took samples of blood at the point of entrance and exit from the liver, kidney or brain. By analyzing what was coming in and out they drew their conclusions and in doing so revolutionized our understanding of metabolism in general and metabolism of fasting in particular. I personally think these two deserved a Nobel, and the reason they did not get even nominated was that studies of "starvation" as it was called did not seem important in comparison with advances in genetics and agriculture that promised to soon make starvation itself obsolete. 

 

PS

jut in case, "intubated" means that they inserted probes into the blood vessels of an organ. This is not a trivial procedure. It requires great skill, else it could be very risky for the subject of the study (nothing bad ever happened). 

 

PPS

why don't you love me

Edited by xEva, 18 May 2017 - 10:08 PM.

[gill3362]

 

Downside of that is that not only do I love a good creamer in my coffee but I take nootropic supps that are fat soluble, like bacopa for example. So I'd have to take those later which kind of defeats the purpose.  I might take green tea extract instead during the morning. Supposedly this promotes autophagy. 

 

 

You could try some powdered MCT oil or coconut oil in your coffee. Zero carbs, I doubt it will interfere with the fast, great source of brain energy. I like this one.  Just a tablespoon will set you up nice, and the powder form of MCT stays mixed with the coffee.

[Nate-2004]

 

 

Downside of that is that not only do I love a good creamer in my coffee but I take nootropic supps that are fat soluble, like bacopa for example. So I'd have to take those later which kind of defeats the purpose.  I might take green tea extract instead during the morning. Supposedly this promotes autophagy. 

 

 

You could try some powdered MCT oil or coconut oil in your coffee. Zero carbs, I doubt it will interfere with the fast, great source of brain energy. I like this one.  Just a tablespoon will set you up nice, and the powder form of MCT stays mixed with the coffee.

 

 

I saw a video or read something recently where they said it wasn't a good idea to do this because it does something but I can't remember what it was lol. I will try to find the video or whatever and link it here soon as I can.

[Heisok]

Nate, congratulations on how well you did ! Should be an inspiration for anybody coming here to delve into fasting for the first time. Did you end up totally eliminating or even significantly lowering your caffeine intake? Fasting aside, when I go off of caffeine, I feel horrible for days. Malaise, depression, headaches. Could have effected how you felt during your fast, and how it differed from some others experiences.

 

gill3362, I am having trouble finding which MCT's C8,C10 or other longer chains, that are in the product you use. Do you have this information? It also has "Soluble Corn Fiber, Sodium Caseinate, Sunflower Lecithin, Silicon Dioxide."

 

If I were to try a powder, I might try one with just C8 and C10 and no other ingredients. Have you tried the alternatives? Personally, I just use C8 oil from different suppliers as suits me. Not much of a coffee creamer, but I drink it black otherwise.

 

Edited by Heisok, 19 May 2017 - 09:39 PM.

[Nate-2004]

No I did not cut out caffeine. I actually saw that coffee might improve autophagy. I did weaken the coffee during the fast though. After all the things I have read about caffeine over the years, even recently with this fasting attempt, I'm inclined to accept it as a constant in my life. It's likely neutral as far as positive or negative benefits and for that reason it is a net positive in the sense that I enjoy it. No reason to cut it out IMO, though I won't drink it after 3pm so that I can fall asleep easily at 1am.

 

The problem with fats during fasts is that they boost somatostatin which inhibits GH. I'll just stick with EGCG instead which does help with appetite, is better absorbed in a fasted state and actually may help further induce autophagy. I get mine from BulkSupplements.

 

I'm actually doing pretty well on the intermittent fast so far.

[Nate-2004]

Second time around with extended fasting, I'm 38 hours in.

 

I realized that Tums has sugar in it though, about 5 calories worth, I took 1.5 of them yesterday because of the stomach acid issues I keep encountering when hungry. This is making it a whole lot easier but now I'm wondering if that's breaking the fast or killing all the benefits or what. I haven't had any tums today.

[APBT]

If one of your objectives with this is body fat reduction.....

 

Attached Files

•  Intermittent-Fasting_Precision-Nutrition.pdf   561.24KB   13 downloads

Edited by APBT, 27 June 2017 - 10:09 PM.

[Nate-2004]

I've been doing the 5:2 with some modifications, the 2 is really just water for 36 hours twice a week for a couple weeks now. I'll be doing my 5th 36 hour bout of water fasting. I think I'm getting used to it now. I plan to stop doing this on vacation for a break, but when I come back to the U.S. I'll do the 5 day FMD.

 

Has anyone done the FMD? Is fruit allowed? That would make it easy if I could just take a tbsp of olive oil and make my usual big smoothie with fruit and blueberries (2 bananas, cup blueberries, 4 kale leaves, 2 chard leaves, 1 carrot, 1 tomato, 3 tbsp ground flax, 2 celery sticks, a few parsley sprigs, and a lemon squeezed). That's 500 calories roughly, I'd spread it out over a 6 hr period. If fruit isn't allowed, not sure what to do. I hate veggies. That hasn't changed with the fasting. I'd probably just take a tbsp of olive oil, some fish oil, maybe coconut oil and then maybe just ground flax. 

Edited by Nate-2004, 28 June 2017 - 02:27 AM.

[Nate-2004]

If one of your objectives with this is body fat reduction.....

 

Thanks man great read. Fasting needs a lot of funding to research and it's going to be a while before we see enough people doing it to spawn answers to all the questions.

[sthira]

Has anyone done the FMD? Is fruit allowed?

Allowed? One thing I do during a few days of severe calorie restriction (which is essentially what Longo's FMD is) is check my blood glucose and ketones. In my case, fruit definitely raises BG and kicks me straight out of ketosis. Especially bananas. But berries will, too.

I drink a smoothie somewhat similar to yours, I just substitute the banana with an avocado, and it doesn't jack my sugar as much. But it still rises, just not as sharply.

If your worst dietary sin is an occasional banana and some fruit in order to hide the leafy greens you detest, then I'd say you've made significant progress and you're doing very well.

Also as you deepen the fasting experience over time your taste buds will continue to change. So just because you still hate vegetables today here in June 2017, doesn't mean you will continue to hate them into the future after you've practiced more fasts.

I like the quote that this is a practice and not a perfect. Expect setbacks and challenges and two steps left and right, front and back.

Anyway, hey: congratulations, man! I remember months ago when you whined that you could never, ever go without even one meal! That's progress you should be proud to own, man!

How's that Iyengar yoga treating your back issues? Wait: don't tell me you haven't yet...

[Nate-2004]

My back issues are improving mostly through various stretches that both youtube and a physical therapist had shown me. I imagine these are sort of similar to the yoga, not sure. I never did hear back from that lady nearby though. She asked if I'd had an MRI but I hadn't yet and I still haven't yet. It's drained my flex card trying to obtain one.

[sthira]

Meh. Just show up. You'll learn the ropes, everyone does. It helps nearly everyone, so it'll help you, too. But I wouldn't make too much of a big deal out of imaging -- often they indicate breakages that have nothing to do with pain. Scan every single person on earth, and we're all kinda fucked up.

[gill3362]

I agree with sthira that Longo's FMD is essentially extremely calorie restriction. 

However, if you wanted to stick to the study criteria strictly. There a plenty of resources for that. 

Here is an article I wrote about the study criteria and how it matches up with a product my company provides. https://www.lifebox....nts-explanation

 

If you google around, there are plenty of other resources. Overall, though, I agree with sthira's last response.

[mccoy]

Has anyone done the FMD? Is fruit allowed? That would make it easy if I could just take a tbsp of olive oil and make my usual big smoothie with fruit and blueberries (2 bananas, cup blueberries, 4 kale leaves, 2 chard leaves, 1 carrot, 1 tomato, 3 tbsp ground flax, 2 celery sticks, a few parsley sprigs, and a lemon squeezed). That's 500 calories roughly, I'd spread it out over a 6 hr period. If fruit isn't allowed, not sure what to do. I hate veggies. That hasn't changed with the fasting. I'd probably just take a tbsp of olive oil, some fish oil, maybe coconut oil and then maybe just ground flax. 

 

If we are speaking about the rigorous, non-commercial FMD (which does not relates to packaged food) fruit is not allowed, nor, as far as I understand, cereals nor starchy vegetables like potatoes. The source for this are the references in Longo's book, which maybe by now has been translated in English.

By reading the book, the only esplicitly allowed food are non starchy vegetables and healthy oils (EVOO, avocado, nuts & seeds) and mushrooms.

The food in the packages is governed by shelf life, not only ideal FMD.

The rationale is that serum insulin must be lowered significantly, which lowers IGF1 and free Testosterone. Low glucose also activates AMPK, which downregulates mTOR. Cutting aminoacids also prevents a significant phosphorylation ratio in mTOR. mTORC1 goes to sleep during an FMD or a water-only fast.

...

[shp5]

Hey Nate, Mate helps keep my hunger at bay, I didn't drink it for that reason but the effect was so noticeable I added it to my fasting arsenal. Also get distracted a lot, I try to work a lot while fasting, you'll have to ignore the brain-fog. Don't get stuck home alone, bored, with access to food. Even if you lack energy.

If your stomach hurts you might stretch it manually or get in a release position, I'll write it up later.

Edited by shp5, 31 July 2017 - 09:45 AM.

[mrkosh1]

I agree about heavy whipping cream. It does indeed provide a boost of energy due to the MCTs. However, the problem is those same fatty acids can reduce human growth hormone release. I will say that I've lost weight rapidly on an Atkins like high fat diet and during intermittent fasting with heavy whipping cream, although too much ordinary milk in my coffee or half and half would cause stalls in weight loss.

 

 

You can do it Nate-2004! I've done some extended fasting over the last few months. Here's what worked for me. No promises that my experience applies to you in the same way.

 

 

 

I will say that when I'm hungry, it's all I can think about, distracting myself is useless because I can't focus.

 

 

Yes I found it distracting at the beginning. I found the best way to get through this is to begin the fast as a "fat fast", until I got into ketosis. That is: I'd add heavy cream to coffee (not milk, which has lactose, galactose which are carbs). I found it oddly filling, and it provides some medium chain fatty acids that can power the brain, and I would feel much better.  Why cream on a fast? Because cream is almost all fat, and fat does not provoke an insulin response. The goal is to get switched over to running on fat instead of sugar, to get through the hard part of the fast. Once the body figures out that there is a large store of energy in adipose tissue and switches over to it, one feels much better. It's the transition that can be a little rough. An alternative to heavy cream is MCT powder or oil, which can be bought pretty cheaply. It's probably better than cream. Once the ketosis kicks in, I can withdraw the cream and do a full-on water fast. But even that isn't necessary, e. g.  Valter Longo has published on the fasting-mimicking diet which has results similar to fasting.

 

Another thing that can make people feel sick during a fast (or keto diet, called the "keto flu"), is the loss of electrolytes due to the natriuresis of fasting: the kidneys for whatever reason give up a lot of salt. The homeostatic response is to eliminate fluids to keep the salinity constant. People feel better by taking a salty broth (like the buillon cubes, or veg broth). Or whatever your favorite electrolyte is.

 

I also read and observed personally that exercise is a good natural appetite suppressant. I ride the bike, and doing it on the early days of the fast made me feel better.

 

 

 

Can green tea and coffee be drunk during a fast?

 

Yes, I chain-drink green tea. And some coffee.

 

Another strategy you might consider is: instead of jumping straight into a fast, switch to a ketogenic diet, to get into a state of nutritional ketosis. There your insulin levels should be nice and low, and starting a fast should be relatively drama-free. If you're not familiar with keto, this is a pretty good place to read up: https://www.reddit.com/r/keto/wiki/faq

 

For a while I was alternating between a few days of fasting, and several days of regular (non-low carb) eating. It would take me several days to get back into ketosis when I started the fast, even with exercise. Once in ketosis I felt really good. So I started looking around at how to stay in ketosis when I ended the fast, and decided to try a keto diet. I've been keto ever since then.

 

Jason Fung just posted 29th in a blog series on fasting:

https://intensivedie...lin-fasting-29/

I'd go read through them all. They have practical advice and review relevant literature. I find it helps motivate me.

 

[sthira]

The headline and pitch of this study seem misleading. Fasting for 24 hours in mice is not the same as fasting for 24 hours in humans. We'd have to fast for a much longer period of time to gain the benefits (if any...) suggested here. They're looking for a fasting mimetic, of course, because of their well-traveled belief that "people won't fast because it's too hard or too dangerous..." I beg to differ. More people would be motivated to fast if more studies in actual humans were performed that indicate fasting might actually do important things to slow metabolic aging.

Nevertheless, it's nice to see something being done on fasting; but I wish Sabatini et al would study fasting in humans.


Fasting For Just 24 Hours Boosts The Regeneration of Stem Cells, Study Finds

PETER DOCKRILL 7 MAY 2018

https://www.sciencea...stine-longevity

Fasting Activates Fatty Acid Oxidation to Enhance Intestinal Stem Cell Function during Homeostasis and Aging

Cell Stem Cell Volume 22, Issue 5, p769–778.e4, 3 May 2018


Highlights

•Fasting induces fatty acid oxidation (FAO) in intestinal stem and progenitor cells

•Aging reduces ISC numbers and function, correlating with decreased FAO

•PPAR/CPT1a-mediated FAO augments ISC function in aging and during regeneration

•PPARδ agonists boost and restore ISC and progenitor function in young and old age


Summary

Diet has a profound effect on tissue regeneration in diverse organisms, and low caloric states such as intermittent fasting have beneficial effects on organismal health and age-associated loss of tissue function. The role of adult stem and progenitor cells in responding to short-term fasting and whether such responses improve regeneration are not well studied. Here we show that a 24 hr fast augments intestinal stem cell (ISC) function in young and aged mice by inducing a fatty acid oxidation (FAO) program and that pharmacological activation of this program mimics many effects of fasting. Acute genetic disruption of Cpt1a, the rate-limiting enzyme in FAO, abrogates ISC-enhancing effects of fasting, but long-term Cpt1a deletion decreases ISC numbers and function, implicating a role for FAO in ISC maintenance. These findings highlight a role for FAO in mediating pro-regenerative effects of fasting in intestinal biology, and they may represent a viable strategy for enhancing intestinal regeneration.

[Nate-2004]

Even then it's been suggested that because we are longer lived and can go much longer without food, we don't have nearly the same stress response as mice do to fasting. It may not even happen with humans, at least not without going at least 14 days.

[sthira]

But fasting definitely saves me money! Money I'm putting aside for when real interventions become available. My eating habits are expensive -- leafy greens, crucifers, nuts, seeds, berries.

I'd like to read more research into fasting in humans, though, because it's a powerful practice. Speaking of 14 days, I recently discovered 14 days water only is just too much for me -- I get too weak to be of any use in modern society. Past ten days borders on dangerous. I'd like to try longer fasts in a supervised setting, and I'd like to learn better refeeding techniques. Refeeding is perhaps the most challenging, and probably the most important aspect of longer fasts.

By the way, this is great:

[Nate-2004]

Saves money but makes me miserable, personally, I only fast 24 hrs a week max, and honestly it's probably doing squat for youth. It's just not that effective in humans, we know this. It's not the same as it is in mice or even lower primates.

[HaplogroupW]

 Speaking of 14 days, I recently discovered 14 days water only is just too much for me -- I get too weak to be of any use in modern society.

 

sthira-

If you're getting lean, could you maybe be running into the problem where you can only get fat eflux from adipocytes at a rate pretty far below your daily energy expenditure? If I understood the abstract right (that's all I read), according to this ref it's about 31.5 kcal/lb of fat:

 

https://www.ncbi.nlm...pubmed/15615615

 

So given my BF=15%, I've got about 24 lbs of fat, so I can get a max of  31.5*24=741 kcal/day from adipose. I'm a bit suspicious of that limit. I don't know if they took into account how low insulin can go on a fast vs hypocaloric diet. The lower the insulin, the higher the activity of hormone-sensitive lipase and the more FA efflux. It also doesn't seem to comport with the Phinney and Volek result where they measured respiratory quotient and showed with cyclists who were fat-adapted could burn something like 1.5 grams fat/minute.  But in any case, the idea would be to add a bit of exogenous fat to make up some of the difference between what the fat cells can supply, and what I'm burning.  I've been adding fat to my salty electrolyte broth, about a tablespoon of red palm oil, coconut oil and cream (no protein). Twice a day.  I feel pretty good and energetic doing this on my current extended fast.

Edited by HaplogroupW, 08 May 2018 - 05:51 AM.

[HaplogroupW]

Even then it's been suggested that because we are longer lived and can go much longer without food, we don't have nearly the same stress response as mice do to fasting. It may not even happen with humans, at least not without going at least 14 days.

 

Nate-

Maybe. But I think there's at least a hint that it's not quite that bad in this Longo stuff:

 

https://www.ncbi.nlm...les/PMC4509734/

 

It has data from two-day FMD in mice, and 5-day FMD in humans (multiple cycles of them though). Look, for example, at the mice mesenchymal stem progenitor cells (MSPC) in Figure 2T, and the human MSPC in Figure 6J. Similarish? So maybe 5-day fast in humans is worthwhile.

Edited by HaplogroupW, 08 May 2018 - 05:44 AM.

[sthira]

...the idea would be to add a bit of exogenous fat to make up some of the difference between what the fat cells can supply, and what I'm burning. I've been adding fat to my salty electrolyte broth, about a tablespoon of red palm oil, coconut oil and cream (no protein). Twice a day. I feel pretty good and energetic doing this on my current extended fast.

That's interesting, thanks. How long is your current fast, what's your routine, and how's it going?

I've consumed small amounts of olive oil for healthy fat during previous prolonged fasts; but then I wonder if I'm slowing down the fast? Slowing things down is okay, though, especially in unsupervised conditions. With added oil, the body is presumably running off the added oil? Probably yes. Maybe the oil is softening the ramp of the fast, similar to Longo's FMD -- but less well studied.

One PF goal is to recycle and scavenge whatever broken pieces of compounds the body can find in order to use these as energy to keep me alive for yet another day (until I find food again).

For increased energy while prolonged fasting I drink coffee, which may also be interrupting the fast. Researchers don't know. I'm not fasting supervised in a clinic, and I don't have that option. So I'm making due.

We have so much to learn, and few people are even trying. But I'm convinced prolonged fasting is analogous to sleep: we need less of PF than we need our nightly sleep, but we need it nevertheless. How much we need seems like a basic human right. We need to know.

https://www.ncbi.nlm...les/PMC4509734/

It has data from two-day FMD in mice, and 5-day FMD in humans (multiple cycles of them though). Look, for example, at the mice mesenchymal stem progenitor cells (MSPC) in Figure 2T, and the human MSPC in Figure 6J. Similarish? So maybe 5-day fast in humans is worthwhile.

I think given the human lifespan extension alternatives we have currently (i.e., nothing) that prolonged fasting and calorie restriction are vaguely above nothing. And they cost nothing, fasting is relatively harmless and available to all, rich and poor. When repair technologies become available mass market, I'll drop PF and CR.