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Is fasting safe? A review of adverse events during water-only fasting (2018) (nih.gov)
69 points by rfreytag 18 days ago | hide | past | web | favorite | 132 comments

I am confused by some of the comments in here who seem to see no food intake for more than 36 hours as dangerous or even pathological or assume that you need to somehow "prepare" for that or take certain precautions. Is this a cultural thing?

When I was I student, I ate one meal a day, maybe some snacks in between. Very often, I went without food for a day, simply because I was too lazy / too emerged in some project to leave the house to buy food. Eating the last meal on Sunday evening, not eating on Monday, eating again on Tuesday evening - 48 hours without food. I did this many, many times, and still (in my early 30ies) do it occasionally, again just because I am too lazy to buy food sometimes. It never occurred to me that this could be considered "fasting", because neither did I feel any different after going 48 hours without food, nor did I lose any measurable amount of weight from it.

Days, weeks or even months without food was pretty much the norm until ~150 years ago. If a day, or even a week without eating would be seriously dangerous to your body, mankind would've become extinct a long, long time ago.

You would be surprised how many people have gone trough their life without experiencing real hunger.

I was doing short weekend hike with a friend and the shop we intended to visit was closed. We had to walk six hours without eating. My fried started to panic and would have called emergency services because he was feeling so weak that his hands started shaking. I had to explain it to him several times that if you sit down for a 15-20 minutes the shaking goes away as the body converts fat to glucose. He was convinced that he would die from walking hungry. Yes, physical exercise while hungry sucks, but you don't die in several days.

> He was convinced that he would die from walking hungry.

Do you think that this is a cultural phenomenon? I cannot imagine a person having constant access to food, everywhere, so that he never walked a few hours without eating. You would have to carry a backpack full a snacks everywhere, or you would somehow make sure that a store or some food place is near you, which seems pretty inconvenient.

> I cannot imagine a person having constant access to food, everywhere

I think it's very common in urban environment with middle class people. You may feel little hungry but you eat within hour or so, never hunger pangs or real weakness. When you do hard exercise, you carry sport drinks and snacks. It's not that hard.

It can be different for poor people in the same culture. Maybe the lack of shared experience contributes to the lack of empathy. When people see poor person walking on the street with hunger pain expression in their face, how do people interpret it? If they don't have a shared experience, hungry person may look just angry.

I've easily done 48hrs without food many times in my 20-30s, but usually over weekend, lunch Friday, out on the beer Friday night and no dinner for some reason or other (shit or too fancy restaurant or weird people wanting to eat Sushi on a friday night). Saturday a football game or horse racing but you missed the breakfast start party due to hangover and can't be arsed with the sit down meal some have planned for the evening so roll on to nightclub with the next group. Sunday hangover, rollout of bed late afternoon and fast food (first solids in 48hrs), a few ibuprofen a bit later or sometimes codeine tablets if my back-pain suffering mate had too many spares, sleep, back to work Monday. Sure i'll reach 60 still. Not saying it's smart but people are too bloody scared about everything.

Same. I sometimes go for 36-48 hours without eating because I am busy and forget or because it is inconvenient. It is a small thing and I feel fine when it happens, it doesn't slow me down at all. It would be a stretch to suggest that human biology isn't well adapted to long periods of not eating, since that is a normal state of nature.

I do know people that seemingly need to eat constantly but their diet consists of mountains of refined carbs and are borderline diabetic, so that probably is a factor. Refined carbs have been a negligible part of my diet for a long time.

That would be me if I wasn't married. In college, I'd do just like you did because I'm lazy and don't like eating out (waste of time and money). In high school, when my parents left town in my teens, I would often go an entire weekend without eating because I didn't want to bother even using the microwave and instead played video games or worked on projects.

Now I'm married with kids, and my wife loves food, so I eat regularly. When she left for a month to visit far away family, I reverted to my old self and ate one meal a day, if that. I just don't see food as being as important as other things, so I neglect it unless providing it for someone else (kids or wife).

And my wife is still surprised when I have no preference for a meal (I usually default to fried eggs or cereal, occasionally with a spinach smoothie when she's gone because they're cheap, easy, and reasonably healthy).

> Days, weeks or even months without food was pretty much the norm until ~150 years ago.

People also died younger 150 years ago. Humans as a population are much healthier today overall—we shouldn't look to how we lived 100+ years ago for health guidance.

(I'm not necessarily disagreeing with the crux of your post, as I don't feel knowledgable enough to weigh in)

That seems rather short sighted. Much of the increase in mean lifespan from 150 years ago comes from lower number of deaths at infancy (aka doctors washing their hands). You can probably attribute most of the rest to improved nutrition and antibiotics.

The philosophy behind "paleo" and various fasting regimens (as well as different modalities of physical training) is that living close to what our primate ancestors lived like is probably something like optimal. Starving yourself from time to time, something which is actually practiced by almost all agricultural societies as a form of religious devotion, is probably a good idea. The whole "3 square meals" thing is mostly a product of marketing departments rather than any scientific research.

^ this.

You may be underestimating the snacking then. Your body starts missing a lot of nutrients after going without food for so long

You might have misunderstood me: 48 hours without food were 48 hours without food. I ate the snacks on days when there was food in the house. Or do you already consider 1 meal a day + snacks fasting?

Most people find that hard to believe. IMHO I think we eat mostly out of habit. I found out what hunger really is after fasting a lot.

I have been there (literally), I agree that eat mostly of habit and hunger can be easily replaced by water/coffee. My blood sugar would drop significantly though after 24h-36h and I would feel dizzy. Were you drinking sweetened drinks?

Your blood sugar really shouldn't drop while fasting, unless you do aerobic exercise, have a genetic mutation that prevents you from producing glycogen, or have some other kind of glycemic disease.

No, water and coffee.

Coffee with milk or cream, or black coffee?

that's very interesting and quite impressive.

Is it really that hard to believe that a CS student in his mid-twenties is too lazy to shower, put on clothes and leave the house? :)



>> To our knowledge, this is the most comprehensive analysis of adverse events experienced during medically supervised, water-only fasting conducted to date. Overall, our data indicate that the majority of adverse events experienced were mild to moderate and known reactions to fasting. This suggests that the protocol used in this study can be safely implemented in a medical setting with minimal risk of a serious adverse event.

But is it safe to fast on our own in a non-medical setting?

If only "the majority" of adverse events were mild to moderate known reactions, how many were severe? How many were unusual? And what does the medical setting provide (clearance, planning, monitoring, intervention) that people fasting on their own might lack?

It's safe because humans had to fast. Think about it, humans didn't have a fridge and fast food. Humans had to go through fasting and in now way except the elite have 21 meals a week.

When you read books in history winter sucked because the lack of food. They would normally ration and it would literally be feast or famine. Just the way we evolved was to be able to do this.

While I believe fasting is safe your logic is flawed. If I following your logic, what would the answer be to "Is it safe to not brush your teeth or visit the dentist"

It's safe because humans had no access to dental hygiene. Think about it, humans had neither toothbrush or toothpaste. And there where no dentist. Humans had to go through life without proper dental hygiene.

Obviously, not taking good care of your teeth is not a good idea. Even though our ancestors didn't.

If you eat what our ancestors ate, then you don't need to brush your teeth.[1]

[1] https://www.westonaprice.org/health-topics/dentistry/the-inv...

>Obviously, not taking good care of your teeth is not a good idea. Even though our ancestors didn't.

TBF our ancestors weren't eating much

Didn't say it was a benefit (I think there is a benefit though personally). My logic was that it was a common occurrence that humans evolved with the ability to go through long periods of fasting. You can go 40+ days without eating and live and that seems pretty amazing how the human body has adapted.

Also looks like cleaning our teeth goes much further back then tooth paste (19th Century Invention) https://recipes.howstuffworks.com/ancestors-eat-to-clean-tee...


Edit: It seems HN as a culture has a dislike of self confidence when it comes to health.

Yes, you can take care of yourself for the most part.

Fasting is done by many people in many cultures all over the world.

It seems this is a new concept to US citzens and maybe they are afraid of the idea that health is mostly a personal choice.

HN has a dislike of one-word answers without any hard data to back them up.

If fasting can be undertaken safely by an individual not in a health care setting, how? What is the mechanism for safety? What are some signs that fasting is veering towards unsafe- for that matter, what's unsafe fasting, anyway?

Pick any one on the ways used by all the religions that have been doing it safely for generations.

You should probably be asking is not fasting safe.

Religions have a history of giving terrible advice and using force to harm acolytes and decenters alike.

We live a lot longer than we used to, it's important to have data that backs up your claims. Just saying that people have done it for a long time doesn't mean much.

> Religions have a history of giving terrible advice and using force to harm acolytes and decenters alike.

He specifically mentioned religions that have safe fasting practices, as demonstrated by people who have been fasting for thousands of years. Your argument is a strawman fallacy.

Yeah. I wouldnt follow the advice of the fresh-airians. They didnt last very long. If you are really concerned try Ramadan. Personally, I think the benefits are greater with consecutive days of liquid only diet.

as safe/unsafe as everything else you have/lack enough experience. is lifting safe? depends on you, your experience and your knowledge about the topic at hand.

You should probably start with a less extreme version than water-only, and work your way up to longer durations and more extreme fasting regimes. As with most other things, mentorship and monitoring (as provided in a medical setting) can substitute experience and knowledge

Obviously there are limits. If you fast for too long you die, regardless of the setting.

But the limits are very wide. There's a guy that allegedly fasted for 382 days, eating only vitamins (and under medical oversight, regular blood tests etc), losing 276 pounds in the process (this translates into -0.72 pounds per day, assuming it was all fat that's 2500 calories, which seems like a normal (average) BMR).


For people that come into this and think: “wtf is wrong with someone that they want to starve themselves” there is more to this than meets the eye.

There is more than one type of fasting (more than one protocol - thowing this here: IF with 16:8/18:6/omad, ADF, 5/2, Extended) and there is some science backing this up. some of the benefits of fasting are mind blowing but it’s hard to “swim upstream” when some of our beliefs are so entrenched (examples: not eating is going to slow your metabolism down, not eating is going to make you lose muscle mass, it’s a sing of mental health issues, it’s a eating disorder, breakfast is the most important meal of the day, you need to eat X time per day to keep your metabolism working)

go to reddit and read the side bar for r/fasting and r/intermittentfasting and do a little bit of research/keep an open mind.

Agree, keep an open mind and don't be affraid to try. I don't know how to categorize my IF, I've been doing it for 4 years. Tuesday and Thursday a snack at 14 and dinner around 21. Friday night, saturday and sunday I eat whatever I want. All other days just tea or cofee.

I'm 42 and I feel better than ever.

Just to make sure I understand...

Sunday: coffee Monday: coffee Tuesday: snack and dinner Wednesday: coffee Thursday: snack and dinner Friday: three full meals Saturday: three full meals

Are you able to focus by Tuesday? I feel like I would struggle to be productive.

You get used to it after a while. The hardest part I found was social pressure to eat. So much of our culture revolves around eating that it's hard to do IF with any schedule where you leave out dinner time.

So skipping breakfast is super easy (IMHO) and skipping dinner is nigh impossible.

Skipping lunch highly depends on how pressured you feel to eat with your colleagues. I think one meal a day (usually named OMAD) is also not hard if you don't have lunch at work.

Monday coffee (or tea, mostly tea), Tuesday snack and dinner, Wednesday cofee, Thursday snack and dinner, Friday just dinner, Saturday three meals (or more or less) and Sunday three meals (or more or less).

I'm able to focus any day. Some months I do 1 week when I fast Monday, Tuesday and I eat dinner on Wednesday; body reboot.

I began to fast gradually and this is what I consider my optimal IF method.

it’s a blend of 5/2 and ADF (alternate day fasting)

most people undestand eating all your food for the day in a certain time window (8 hours) to be IF. The 8 hours eat + 16 hours fast is labeled 16:8.

but you know what, you can call it whatever you want as long as it works for you :)

Dinner around 21 (9 PM) would be quite late for me. What time do you then go to sleep?

I feel like the timing of supper is a cultural thing. I prefer to eat later, but it sucks trying to do that in America, unless you want fast food. But I fell in love with Spain because it was honestly the optimal meals times for my body. Wish it was easier to do in America, at restaurants.

I'm from Argentina, wake up at 6.15 and go to sleep at 22.

IF seems relatively commonplace at this point. That said, its physiological value over other calorie restrictive diets is dubious:


another interesting point is that fasting and intermittent fasting is not a diet.

IMHO all diets fail. If you attack it as a problem, you find a solution, do that, it works and you considered it solved you’re gonna fallback to your own habbits.

the way I look at eating and other aspects of my life is that I want sustainable change. If I see me doing something for the rest of my life and incorporating it into my routine/lifestyle I do it. If not I will not.

Sustainable change is what you want. Not a quick fix. Not a miracle. Not a pill.

lol. sorry but that’s not true. calories are important but they’re not all that matters (another way of saying this is if you overeat you will get heavier).

i can tell you that when you eat matters a lot. i can also tell you that a calorie from sugar is not the same as a calorie from lean meat.

it’s not the energy value, but the hormonal effect it has on you and the results cravings/hunger/binge eating.

if I’m ever going to become a minimalistic nutrition guru my advice would be this: cut out sugar and refined carbs, sleep, exercise. that is all. good luck pedaling this and makinf money of of it :)

While this is a hotly debated topic, it's not an argument I made. It's also irrelevant to the topic. You can do IF and eat candy for eight hours.

The meta studies show that IF offers no additional benefits over similar caloric deficit approaches

So often do I hear "You skip breakfast?? But its the most important meal of the day!".

yes. even corporations that sell breakfast cereal agree. you see you need to start your metabolism. think of your metabolism as a fire that you need to light up in the morning /s

Who fasts with distilled water? Is this a thing now?

It's dangerous because it will dilute electrolyte concentrations in your body. Drink tap/bottled water. Distilled water is completely unnatural to the body and should only be consumed in emergencies when you literally have nothing else. Even then it's still probably not a good idea.

There's literally no benefit to choosing distilled water over tap/bottled water.

Water-only diet is fine, but it's possible to make it unnecessarily uncomfortable (tired and headaches)

Idiocracy was right. You need the electrolytes. In other words, you should drink water with enough magnesium, sodium and, potassium. Many mineral waters, zero-calorie sports-drinks and low-sodium salts like Pansalt contain the right mix.

Indeed, it's surprising they went with distilled water exactly for this reason.

The two patients with most serious side-effects experienced dehydration and hyponatremia. This supports my view that it's important to maintain electrolyte balance during fasting (or other types of dieting like low-carb). When doing these kinds of practices I usually add some salt to water (or other electrolyte solutions if needed although there might be some sugar in them).

I think this should help with the common complaints they saw like headache, fatigue, even the cardiovascular related issues. I gotta admit that as far as 'insomnia' goes I don't think electrolytes will help with that... you probably need some combination of fat/protein/carbs to get good sleep.

Most people who fast for more than 36 hours recommend electrolyte supplements. Now they even have "snake juice" recipes. If fasting takes off, I bet there will be commercial snake juice products for long term fasters.

Could magnesium supplementation help with sleep?

Yes, it is.

The better question: is it safe to eat/snack/graze chronically? Type 2 Diabetes seems to indicate it is not.

I did 12 days (300 hours) on water, drinking Snake Juice off and on and seem to be fine. I lost about 15 lbs during that fast and regained about 5-6 lbs afterwards. I did notice my skin was a lot healthier and I felt my mind was much stronger, everyone said I looked younger. I didn't suffer any type of medical problems afterwards and continue to fast at least once a month for 2-4 days on just water and a daily 18/6 IF. I rarely get sick anymore (colds, sore throats, etc). My weight has come down to a healthy level (lost 70+lbs over the last 1.5 years).

You just have to get over the fear of not eating and understand that missing a few meals or not eating for a few days can make you feel better. It's sort of the same as quitting smoking, you free yourself from destructive living.

and learn to keep your mouth shut about what you’re doing

Fasting and duration seems to be an individual discovery, until more scientific data measurements about amino acids, genetics, immune state, glycogen levels, etc are established. I've water fasted over 50 times in the 15 months ranging from 16 - 48 hours to help with Lyme and other tick borne pathogens. I've found it to be highly anti-inflammatory and have yet to feel bad (maybe 3 very mild headaches). For example, my vision acuity improves around 15 hours into a fast every time (noticeable when reading). I've even jogged or walked miles 30 hours into a fast, depending on residual glycogen levels in the blood and muscles. The glycogen should be consumed from the liver, blood, and muscles (partial) before entering ketosis. With that said, it's not for everyone and it is probably better to slowly increase the duration of the water fast to evaluate individual response. Also, hundreds of millions in the Muslim culture practice a complete daylight fast every year with minimal side effect. That should be significantly significant ;-).

I would be interested in a comparison to 'total' fasting, i.e. abstaining from both solid food and liquid. This is the most commonly practiced religious practice (and so has a thousand year history). It would be interesting to know what the differences were, if any.

In my own experience, somewhat unintuitively, total fasting is a lot easier than water-only fasting. I ascribe this to the digsetive system kind of shutting down after several hours of complete fasting. It feels like the stomach shrivels up, and hunger pangs become fewer and further between as time passes. Whereas going without proper food, but consuming water or small snacks, I feel very uncomfortable and usually get a headache.

I’m not aware of any traditional religious fast which requires abstaining from water for even a 24 hour period.

Traditional eastern and western christian practices did require a fast from water before liturgies but the church services were always held at noon or before due to this.

I see Ramadan does involve a fast from water, but only during daylight. Not sure about other practices.

Dehydration is real and will harm and kill quickly. I wouldn’t equate small snacks with water from this perspective - maybe snacks are keeping your body from entering ketosis and burning fat efficiently, thus the headache?

The customary Jewish fast on day of atonement ("Yom Kippurim") is ~24-26 hours without food or water.

Indeed, it makes no sense to me. But it does exist.

An interesting side effect is an increased number of deliveries among fasting late-term pregnant women (which are not required to fast -- in fact, are required NOT to fast, but some do so anyway) -- as if there's delivery mechanism that says ("oops, mommy can't find food with you inside, perhaps if you go outside it'll work better").

Going for a long period of time without water is intuitively a bad idea for your health. I think this is the reason for this study being water-only.

It also makes sense from religious perspective, since a religion will prepare you for another life which is only attainable by dying, with no apparent intention to give you a good and healthy life on Earth.

> It also makes sense from religious perspective, since a religion will prepare you for another life which is only attainable by dying, with no apparent intention to give you a good and healthy life on Earth.

Did you study all of the religions out there to make this claim? If so, I'm interested in seeing a summary or a write up. Otherwise, do not make blanket statements full of conjectures and imply that all religions are suicide cults of some sort.

The most simple way to refute this is that any religion interested in sustaining itself is not interested in harming its followers. Not to mentions some religions that establish not just dietary practices, but also financial, economic, and social practices for balance and prosperity.

This is my life experience and deduction, you are free to refute it by example instead of trying to tell me what to say or think on the internet. Right now all I see is "you told me the truth on a subject I am sensitive about so I will say things to hurt you"

I will be more than happy to relay my opinions and discuss further with a video conference if you do not find this medium adequate for discussion.

A simple example (I'm sure there are many more): Islam explicitly mentions the need for balance between the Spiritual and the Worldly pursuits. For instance[1]:

    "You owe a duty to your Rubb (Lord), you owe a duty to your body; you owe a duty to your family; so you should give to every one his due. Abud-Darda' came to the Prophet (ﷺ) and reported the whole story. Prophet (ﷺ) said, "Salman is right".
It also introduces certain rulings as to preserve social coherence and balance (e.g. outlawing interest as it is an exploitative practice that feeds on the needy, requiring a portion of each person's wealth to be distributed to charity each year, etc.). Life preservation comes first, so things that are prohibited become compulsory to sustain it (e.g. pork is prohibited, but if someone ends up in a situation where only pork is available for them to consume, otherwise they would starve to death, they are _obliged_ to consume it to sustain themselves and not die[2]).

There are many more examples, but this is what came to my mind in a couple of minutes.

[1] https://sunnah.com/riyadussaliheen/1/149 [2] https://quran.com/2/173

I don't see the notion of wellness repeated anywhere in the Quran. "ok you can eat pork in this situation" is not the thing I've had in mind. Neither is the requirement to stay dehydrated for extended periods of time.

The whole idea of halal meat is disputed (since almost all of europe, china and american continent as well as australia thrives on pork) so I am beyond a doubt convinced it is a middle eastern bubble of safe-space where any opposing idea triggers people.

Anyway what I mean by wellness is a holy book commandment (not skme hadith) to stay healthy without emphasizing afterlife, djinns, devils or angels. Would be nice if you have another two minutes to write a dissertation about that.

Authentic Hadiths (like the one I cited) are used to deduce rulings, much like rulings are deduced from the Quran. For example, the Quran prohibits usury/interest. The Hadiths expand on the different forms of usury (lending money for money plus profit is just one form of usury, there are several more).

I think this is enough to settle the discussion, as the Hadith I listed in my previous post mentions an action of a companion that was explicitly approved and encouraged by the Prophet ﷺ. In other words, this is part of the religion.

Here is another authentic Hadith that explicitly requires balance between rituals and physical needs[0]:

    but still I observe fast and break it; perform Salat (prayers) and sleep at night and take wives. So whoever turns away from my Sunnah (Path) does not belong to me

    Allah is Beautiful, He loves beauty
Referring to how one should dress nicely and cleanly if he can afford it. And again[2]:

    A strong believer is better and dearer to Allah than a weak one, and both are good
Strength in this specific instance refers to physical strength, not strength of belief. So people are encouraged to take care of themselves and not be weak and frail.

As far as fasting goes, the Quran explicitly mentions that Muslims are required to fast the same way as those before them were required to fast (e.g. Jews and Christians)[3]. It then goes on to exempt those who are weak or unable to fast (e.g. the elderly), or those who are traveling[4]. Clearly a form of caring for its followers and not overburdening them.

I don't see what Halal meat has to do with this discussion to be honest. Pork is prohibited, I don't think there is a text stating the reason behind it, be it health related or not. Different people may have different conjectures about the rationale behind the prohibition. At the end of the day; however, this prohibition is a form of submission if one wants to adhere to the teachings of the religion.

I feel the discussion veered off the original point. I mentioned Islam as an example to refute your point that all religions are cults that want their followers to suffer and live miserable lives, so as to shorten their lifespans. I then gave counter points that is not the case, as Islam exempts certain requirements at the time of need. It also provides mechanisms to preserve social balance, not just at the individual level, but at the social level by prohibiting certain exploitative and destructive practices, requiring financially able people to donate to charity, requiring that people treat their neighbors well, and many more.

A final example that comes to mind is that there were many Companions that were wealthy. Not once were they discouraged from pursuing wealth, or had their money taken away from them. As a matter of fact, we see the opposite. A man wanted to write in his will to give away his entire wealth to charity, the Prophet ﷺ told him that he should donate at most 1/3rd of it, and keep the rest for his heirs.

[0] https://sunnah.com/riyadussaliheen/1/143

[1] https://sunnah.com/riyadussaliheen/1/612

[2] https://sunnah.com/riyadussaliheen/1/100

[3] https://quran.com/2/183

[4] https://quran.com/2/184-185

Cultural evolution suggests that, regardless of intention, these practices which have become mainstays of popular religions around the world, cover some type of benefit to survival, reproduction, or intellectual spread.

Or to spiritual practise. The idea that they have to have a mundane use strikes me as wilfully blind to their intended purpose.

Considering the infinite variety of ways to exercise a spiritual practice, and that many (perhaps most?) of them have died out in favor of the dominant religions and spiritual practices that survive today, I'd actually say it's willfully blind to ignore the likely impact of religion on survival and reproduction. It's simple game theory. The religions that survive today outcompeted the others.

That, or terrible peer pressure. In my opinion, Occam's razor suggests the latter.

That's fine. I think it's just conventional wisdom that makes this seem like the "simpler" solution, and I'm a bit allergic to that, but to each their own.

>It also makes sense from religious perspective, since a religion will prepare you for another life which is only attainable by dying, with no apparent intention to give you a good and healthy life on Earth.

I'm not seeing the connection; religion allegedly prepares people for life after this one, so it encourages suicidal tendencies like fasting? I's biased because I'm religious and have generally fasted once a month or so, but I imagine it's more to develop delayed gratification and gain insight into the self, similar to meditation.

His argument doesn't make sense at all. Clearly biased (not to mention ignorant) as you pointed out.

I don't think any fasting or religion is needed to develop a sense for economics. According to the marshmallow test, all you need is to be born rich.

you can do a water fast for weeks and you’ll mostly be fine. your body has evolved to tolerate the absence of food and actually has mechanisms to deal with it. all that fat that you’ve been storing? gonna be converted to energy through ketosis. (in case you have a very low % if body fat you will be in trouble, but this does not apply to 95% out there)

if you fast totally (dry fasting) things go bad pretty quickly. Dehydration is the thing that it’s going to get you and there is a non-zero chance you are going to die because of it. Short of experimenting with this 1, maybe 2 days I would not recommend it.

Total fasting has rather an inbuilt time limit due to medically dangerous dehydration. The usual way it is practised is for part of each day, rather than continuously. So it's not really comparable to water-only fasting that can be practised for weeks on end.

As someone coming off a three-day water fast (five days was my max), all I can recommend is that you try it for yourself. The lightness, clarity, and self-assuredness that it builds is lovely.

hahaha. that’s not healthy for you /s

seriously, as someone that has done extended fasting at times (think weeks) my advice is not to jump into the deep end of the pool.

Try eating all your food in an 8 hour window for starters and after that do several fasts with increasing duration s 1,2,3,5,8... days of fasting (fibonnaci fasting)

the other thing to consider is that if you think or see something is wrong yoh stop. fasting is mostly safe, but there are edge cases were yoh will have a bad time.

and last piece of advice is that I have noticed people that eat sugar (lots of sugar) have an exceptional hard time fasting (the hunger is unbearable). So one thing to try is to kick the sugar habit before fasting (at that point even if you decide fasting is bullshit you’ve kicked sugar to the curb and that’s huge in its own way)

Not only electrolytes but the lack of fibre is also a big problem when you fast more than a few days.

Body needs fibre to maintain a healthy gut flora. So when the body lose the flora, it will struggle to digest the food, take the vitamins and nutritions from it etc. at the end of the fasting period.

This is not only something I read from articles but also something I have experienced for a long time by the way. So please bear that in mind, keep your gut flora healthy and your life will be easier.

> Body needs fibre to maintain a healthy gut flora.

Do you have a good link that explains that further?

I am on mobile, couldn’t find the original article but this one seems good enough. Please take a look.


I don't think this has been well established. We have several examples of people who have eaten nothing but animals products for long periods, without adverse health effects.

The Chief complaints table had some interesting tidbits:

> Cancer: Breast (11), Andrologic (10), Lymphoma (3)

> Tumor: Neck (6), Breast (1), Colon (1)

So a nontrivial number of people reported cancer as a side effect of water fasting.

I suppose you'd probably want to review the standard correlation-does-not-equal-causation fallacy, but still.

These are the complaints and issues that brought patients to the facility that administered the fast, not "reported as a side effect of water fasting".

> Table 1 describes chief complaint categories as total counts and as a percentage of total visits. A patient could have had more than one chief complaint per visit. Quality of life, including prevention and fatigue, was the primary reason patients visited TNHC (n = 384, 50%). Other major chief complaint categories included the cardiovascular (n = 193, 25.1%), musculoskeletal (n = 147, 19.1%), gastrointestinal (n = 122, 15.9%), and endocrine (n = 107, 13.9%) systems. Following prevention (n = 358, 46.7%), hypertension (n = 152, 19.7%) was the largest chief complaint category.

> So a nontrivial number of people reported cancer as a side effect of water fasting.

Reporting each and every condition, however unlikely to be caused by the subject of study, is a necessary part of a study into adverse effects. And for good reason, because it allows later research into surprising causal links, by evaluating mere correlations from different studies.

It doesn't mean the participant thought the adverse effect had anything to do with fasting.

tl;dr: yes it mostly is.

Only for Americans in labs, though. It's totally fine for the rest of the world and our ancestors. I'm an American not in a lab and I do it all the time with life-changing results.

I think you think I am saying the opposite of what I think I am saying.

Apologies, my mistake!

Common pharmaceuticals (even vaccines) have known (and some extremely debilitating) side effects.

While the conclusion seems reasonable (ie, some people have adverse affects to not eating) it's by no means a condemnation of fasting.

Fasting is the universal method of allowing the body to heal itself, animals fast to heal naturally. (ie, no medicine actually heals only compliments/supports healing, the body does all the real work)

>Fasting is the universal method of allowing the body to heal itself

This sounds like folkloric nonsense.

Check writings by Valter Longo. The two principles are autophagy during the fast getting of bad cells (precancerous, etc...), and hormones typically only present in kids during growth periods reappearing during refeeding (eating after fasts longer than a few days).

When you try it for yourself, you realize that it's not.

That's exactly the mentality that keeps wives' tales circulating.

How often do home remedies "work" because of placebo and/or simply time?

Ok, don't try it. :)

Wive's tales and home remedies still circulate because they often work. Of course, you're not going to read that on Hacker News because it's biased by people wearing modern American blinders that don't have the humility, courage, awareness or something else, to just try for themselves. I was that way until I tried psychedelics, meditation, pranayama breathing, lucid dreaming and many other alternative modalities just two years ago.

All love--good luck on your journey!

>American blinders that don't have the humility, courage, awareness

No, it's about having some degree of scientific rigor, as opposed to blind anecdote.

Scientific rigor is not just about gathering people as lab subjects, experimenting on them and publishing your findings in peer reviewed journals. In my experience, the strongest science, where the deepest knowledge arises, is by systematically performing experiments on yourself. This isn't possible for all things, but it's 100% available for fasting.

Thanks for the conversation, best to you.

It's how wild animals that are wounded or sick heal. How is this "folkloric nonsense"?

Animals fast on purpose to facilitate healing? Do you have a source for this? I suspect some are forced to fast because they are too injured/ill to obtain food.

A positive impact from entering a massive caloric deficit when the body is actively burning calories is counter-intuitive.


Not GP. I don't remember where I read it about wild animals, but my dog would have the occasional "low energy, don't want to play" day, followed by a couple of days of not eating, and then being super-energetic when he went back to eating.

On one of these occasions, I took him to the vet, who said he had a fever, likely of viral cause, and that him losing appetite was perfectly natural and likely helping him heal.

When I'm sick I lose my appetite (and don't eat, sometimes for a few days).

Don't you lose your appetite when you are sick?

Sometimes I also get constipated when I get sick. Should I start practicing fecal retention?

The logic of your argument eludes me.

lack of will to eat --> not eating until will returns --> feeling better

is supposed to be analogous to

lack of ability to poop --> trying not to poop --> ?


No, unless I'm so sick I just sleep all day, I'm usually extra hungry.

The positive impacts of fasting are supposedly due to increased efforts by the body to scrounge and scrape for calories, which up-regulates processes that have the effect of clearing undesirable built-up matter/cells/etc.

Compared to what ?

Is it safe to eat 3 times a day + snacks, mostly over processed, calorie dense, low micro nutrients food ?

Food is like most things, moderation/balance is key. I have no doubt fasting can be beneficial in some cases just as I have no doubt that the typical western diet is universally bad.

This new fasting trend is just the blowback of the over abundance / over consumption of low quality food we experience pretty much everywhere in US / Europe.

If you read the article you will see that the results and conclusion might be in line with what you expect. Academic papers don't necessarily follow Poe's Law in their titles ;)

It is bad form to criticize posters on HN for not reading the article they’re criticizing. Oddly, it seems to be less accepted than not reading the article one’s criticizing.

I don't know what gave you that impression, but it doesn't match my experience on HN at all.

Discussions based on headlines alone tend to be accepted (especially if the poster mentions they haven't read the article), but "the article addresses your questions <here> and <here>" is usually the top reply.

There's a line between criticizing someone for not reading the article (or insinuating that they didn't read it, per the guidelines[1]) and stating that such-and-such claim is found in the article.

Please don't insinuate that someone hasn't read an article. "Did you even read the article? It mentions that" can be shortened to "The article mentions that."

[1] https://news.ycombinator.com/newsguidelines.html

In fairness, I tend to see two types of responses:

One of the kind you mention - “the article actually says ...”, in which the respondent goes to the effort of basically summarizing the article OP didn’t bother to read. Those generally catch moderate upvotes.

Then there’s the more blunt variety, along the lines of RTFM. Those catch solid downvotes.

Frankly, I’d rather neither existed, and posts that clearly didn’t bother looking at anything but the headline were just flagged and deleted.

I know this and generally agree. In this case it's the number 2 upvoted comment so I thought it worth pointing out.

> the typical western diet is universally bad

As if there is a "western" diet.

Even just remaining in Europe, the typical diet in Italy has nothing to do with the typical diet in Germany.

And while southern countries and northern countries tend to have more similar diets, even between them they have big differences.

Same goes for "eastern diets". China and India, to pick just two, have completely different diets.

Criticize overcompsuntion of low quality food all you want when it occurs, but I think that broad-stroke generalizations like "western diet bad" are not useful.

Go anywhere in Europe or in the US, people eat basically the same things. Globalisation took care of it, there might be some local variants, especially in rural areas, but in big cities there is close to no differences between NY, SF, London, Paris, Athens and Berlin.

At the end of the day >50% of people in Europe and in the US are overweight or obese. Every country adopting our diets are following the trend, have a look at Latin america and Maghreb.

We can argue all day long about the details but it doesn't change the facts that we're fucking up in major ways.

I'm not talking about traditional dishes that take 24 hours to prepare and that you eat once a month when you visit your grandma, I'm talking about what people actually put in their mouth days in days out, and it's frozen junk, fast food, over processed meat, excessive amount of carbs, etc ...

Damn, my colleagues can't stop asking me why I eat "so healthy" but I just eat fresh food / things I cook myself. There are 300-400 people in my office, we're literally ~20 to do that.

- http://www.euro.who.int/en/health-topics/noncommunicable-dis...

- http://www.ipsnews.net/2018/11/alert-hunger-obesity-rise-lat...

typical diet in Italy has nothing to do with the typical diet in Germany.

That's not really true. Both build a lot of their meals around a boiled starch, a grilled or fried protein and a vegetable dish, often prepared separately. It is not uncommon that this dish is primarily made up of raw vegetables. The starch and protein component almost always makes up the bulk of the meal. Both use a lot of dairy based sauces and/or a sauce made by thickening a meat stock (either pre-made or by de-glazing the pan they fired their protein in). Bread and other baked goods are a common component in many meals in both counties, often served with vegetable or dairy fat.

Is there any (national or regional) diet that isn't based around a starch, a protein, and vegetables, with the starch and protein making up the bulk of the meal?

The traditional Inuit diet is obviously much much lighter on starches and vegetables.


Is that a national or regional diet anywhere?

>>a grilled or fried protein I don't know where calling meat "protein" come from, but for me it seems so wrong. There are other sources of protein and more than protein in meat. So why not call meat for meat? I am almost sure you talk about meat, but could also be cheese or another natural protein source, since grilling or frying a protein shake will probably not be a great success.

They said protein because that would also include such things as tofu, fish, and eggs; none of which are commonly called "meat". You're being overly restrictive by trying to move to the term meat.

ok, so a protein source, or a source of protein, would cover it. Might be me getting old, but the term "a protein" rubs me the wrong way

It's just another example of an English word having multiple meanings. The listener (or reader) has to divine which one was intended by context. Much like the word "organic".

Protein is used this way quite a bit when talking about diet.

It is an NIH study which to me implies rigor; including controls.

You cannot assume this is an NIH study just because the website hosting the PDF is from the NIH. The NCBI is somewhat of an online repository of papers and citations, nothing more.

The study was published in the journal BMC Complementary and Alternative Medicine, and none of its authors are affiliated with the NIH, judging from their affiliation statement in the paper itself:

Author details

1 AOMA Graduate School of Integrative Medicine, Austin, TX 78745, USA.

2 NoviSci, Durham, NC, USA.

3 TrueNorth Health Center, Santa Rosa, CA 95404, USA.

4 TrueNorth Health Foundation, 1501 Pacific Avenue, Santa Rosa, CA 95404, USA.

The report appears rigorous, but it notes in several places that the data is not acquired in a rigorous way as it was not intended to be used to make such assessments.

As to controls:

>"the relative safety of water-only fasting is necessarily descriptive in nature as we did not identify a comparison group(s)"

It's a good paper.

I was left wondering why people attended the facility. A 9 day water only fast, with limited activity, sounds pretty extreme for a 70+ yo.

Bmc on the nih website nowadays basically hosting nih-founded research papers. Not just papers published from nih

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