[asar]

It's such a shame that there isn't more research in this area. There are so many seemingly wondrous effects on human health that would need thourugh testing.

Apart from physiological benefits though, the mental aspect of fasting from my own experience can be quite exciting as well. A 7 day fast was the longest I did so far, but 72h really hit the sweet spot for me. It was like a journey through my mind, I got challenged in very new ways to break the fast and also questioned my purpose in life a lot, as I seemingly live to eat. It was quite shocking to realize how much time I spend during a normal day to: buy food, prepare it, consume, dispose, cleanup etc. The rewards of fasting to me were long phases of absolute clarity and great concentration.

[seer]

While I’ve done similar fasting myself, with the same wondrous effects you describe, I want to point out that it seems this might be a lot harder to do for young women (in child bearing age). My partner tried to replicate what I did since I was hyping it so much, and failed miserably. Later we learned that the female body reacts much more violently to the lack of calories than male ones, and its a lot harder for them. Or maybe she had other compounding factors.

While she couldn’t do the several day fast, we found out that it was quite feasible to do the “one meal per day” thing, which shares a lot of the health benefits, and its a lot more forgiving.

[mahathu]

I'm kind of doing "one meal per day" right now, not because I'm fasting on purpose but just because I don't enjoy eating (or cooking) more than once in a day. I mean I like to cook but doing it for over an hour every day just becomes a chore.

I was under the impression that this was really unhealthy though. My BMI is 19 so I'm close to being underweight. Isn't this unhealthy? Do people fast and not lose weight?

[strogonoff]

I’m sure many would be quick to jump to numbers on how much you are supposed to consume/burn in a day, but I really don’t think eating too little or too much is by itself an indicator.

The underlying psychological issues and associated stresses is what IMO qualifies as “unhealthy”, in which case corresponding under- or over-eating could result in malnourishment or excess weight[0]. However, in absence of these issues or other factors suppressing your body’s hunger/satiety messaging, not eating some “standard amount” shouldn’t be an issue on its own[1].

I happen to know a person who fasts routinely. In case of that person it doesn’t seem to be motivated by hidden psychological issues (he does not strike me as a person who could be suffering from body dysmorphia/anorexia) but by a conscious health choice. As an example of his logic, recently he got COVID and from his words he “simply” didn’t eat for two days and was right back on his feet feeling great. It’s not my place to question his choices, and I myself try to space meals to spend 14–16 hours without food every day since it seems to leave me feeling better, so it was surprising to hear but not too outlandish. He is not bulky but not skinnier than me either[2].

(I’m not a doctor, but from a cursory check medicine does seem to classify eating disorders as “expressive”, i.e. indicative of underlying issues. I don’t know how medicine treats under-eating without a cause, I certainly hope they don’t try to force-“treat” someone to make them eat at a level medicine considers “normal”.)

[0] For the record, I don’t think one can truly address those root causes just by eating less or more.

[1] In fact IIRC lower metabolic rates have been correlated with longer lifespans, at least in mice and in snails if not in humans.

[2] I’m slightly underweight, and can eat quite a bit without gaining much weight. My sister is similar, and she quickly gets low blood sugar shakes if she doesn’t eat enough. I guess it’s a sign of fast metabolism.

[thechao]

> I’m slightly underweight, and I can eat quite a bit without gaining much weight

Interesting! Here's a challenge for you: could you buy — and eat — 5000 calories of chips/candy/soda per day for the next 90 days. You may not walk/run more than 5km/day, nor engage in other exercise for more than 30m/day.

Please weigh yourself before & after this experiment.

[strogonoff]

I used to (?) stress-eat periodically (especially before I started trying to space out meals) and could go a long time without any exercise so pretty sure I approached this at some point or another in my life. Don’t weigh myself regularly but there were no signs of gaining weight. Maybe I’ll become heavy in my thirties, but so far all of that goes neither into fat nor into muscle.

[femiagbabiaka]

Weight gain or loss is all about calories in versus calories out. It is possible to exceed your TDEE in one meal, just a little difficult or unlikely. Whether or not this is unhealthy or not is dependent on the person. I will say that I worry that many in my generation are developing eating disorders and calling it fasting/OMAD/etc.

[Fritsdehacker]

For most males it should be possible to get enough calories and nutrients from just one meal, but I would not say easy. It is far easier with two meals, or maybe a time window of 4 hours.

It's probably also better to ease into it. So start with an 8 hour eating window and slowly decrease the window.

Getting enough calories and nutrients can be a challenge and is far from easy with the "standard western diet". I would really recommend seeking advice from a professional.

[itsoktocry]

>Getting enough calories and nutrients can be a challenge and is far from easy with the "standard western diet".

Have you been to a grocery store in the last 100 years? Getting enough calories and nutrients is dead simple, our stores are overflowing with fresh fruit, vegetables, nuts and meat. What is the "standard western diet"?

[wutbrodo]

> What is the "standard western diet"?

https://en.wikipedia.org/wiki/Western_pattern_diet, also referred to throughout the article as "The Standard American Diet".

[Fritsdehacker]

Under normal circumstances the difficulty with the western diet is getting enough nutrients, but not too much calories.

I meant the combination can be a challenge if your on a narrow time feeding window.

[wanda]

Sorry but that's kind if anecdotal. You're extending the case of one woman age (x) to all women age (x).

Yes, you say "maybe she had other compounding factors" which is equivalent to saying her case was idiosyncratic. In which case, why try to generalise it at all then?

When I look around the city, I see a lot of underweight women of all ages, including childbearing age — whatever the hell we're defining that as.* Many of them will be underweight by skipping meals, full on fasting, or eating and forcing themselves to throw it up later. This is the society, the mentality we have created.

Some of them I am friends with, others I have never met but write about it. Some claim to struggle with fasting, others fast and mention nothing about the difficulty or ease, and others struggle to eat enough. And some eat whatever they want and don't regulate it at all.

The takeaway is that when it comes to nutrition, there are a lot of factors and every case is idiosyncratic. There are no general rules other than "eat so you don't die", "don't eat so much you explode" and "don't eat toxic or corrosive chemicals". And even then, different people will have different tolerances to not eating, eating too much, and eating poison.

Nutrition is poorly understood, poorly communicated, and the driving factor behind the freight train of bullshit marketing telling people that they need to be wafer-like, elven creatures.

Full transparency, I'm underweight according to what I'm sure is actually a pretty shoddy measurement of weight...ness, but I don't do anything special. I fast quite a lot but I don't actually have a fasting regime, it's not planned, I just don't eat for extended periods of time.

When I do eat, it's really not a remarkable experience so I don't feel a need to change my behaviour. I eat enough to not die or suffer health problems thus far.

_____

* Since it will be a subset of {all ages}, my reasoning is covered.

[moonchrome]

>Sorry but that's kind if anecdotal.

He said they later learned it's known that women react to fasting differently and can have negative side effects, which we also discovered from our doctor when trying to get pregnant - so don't really see anything anecdotal there.

[wanda]

It's not anecdotal because your anecdote matched the parent's anecdote. Okay. Scientific method looking robust in this field.

My point is that any nutritional thing is anecdotal because people don't neatly slot into a category when it comes to nutrition.

[TimSchumann]

I really think a 7 day fast should be 'mandatory reading' as far as life experience goes. You learn a lot about yourself.

Also echo the mental clarity side of fasting. The weight loss was great, but how I felt was even better.

The crazy thing is, if you can get to 7 days, anything past that is just mental and you can go as long as you have the body fat to sustain the fast, provided you're keeping an eye on your electrolytes and not drinking too much water.

[egeozcan]

I'm not sure if starting something like a 7-day fast without medical supervision is a good idea, and I'm also not sure if any medical professional would allow you to do that, just thinking out loud.

Don't you think it's too dangerous to name it essential life experience and recommend it to random people on the internet?

I'm really asking, I'm not knowledgeable about this at all, and my questions stem from pure gut feeling.

[TimSchumann]

I feel 100% confident, based on my experience, in saying that almost any healthy adult has the ability to fast for 7 days without any negative consequences to their short term or long term health. In fact, I'd say there's only positives.

Obviously if you feel differently, talk with your doctor. I am not a doctor, and this is not medical advice. I thought that went without saying on the internet, but just to be extra careful, there it is.

Couple of caveats in the almost. Pregnancy, Eating Disorders, Elite Athletes functioning at under 5% bodyfat, and again the key word being _healthy_ here. If you have any kind of condition, disorder, disease, etc. obviously talk to a medical professional.

Most people just don't have the desire to do it, and if you're not used to fasting and eating a standard diet, the first few days will make you feel terrible both physically and mentally. Just like anything, it gets easier with practice.

[wutbrodo]

> If you have any kind of condition, disorder, disease, etc. obviously talk to a medical professional.

That's sort of the rub in cavalierly recommending things to the general population, even when they're only somewhat extreme. There are plenty of undiagnosed conditions out there, and the further you move from the center of the distribution, the more you're going to sweep up potential risk in ways that aren't easily caught with a simple "not applicable if".

I say this as someone who fasts pretty often, though usually not more than 2 days. It's the same reason I wouldn't recommend everyone go out and take 200 mcg of LSD, "unless you have a mental health condition". This world of perfect information about one's own health that you're imagining simply doesn't exist. (Again, I say this as someone who thinks LSD is wonderful and salutary and has recommended it to many many friends in person with the appropriate personalized caveats).

[milchek]

I also question if 7 days is safe for most. I don't recall exactly when and a quick search now yields a lot of random gimmicky fasting product sales sites with blog posts written to generate traffic that aren't scientific enough, but I do recall that there is a point (after 72 hours?) where your body starts breaking down muscle and that prolonged fasting is dangerous as your organs get hit next?

Perhaps someone here with medical experience can chime in, but I agree 7 days seems a bit extreme for most people.

[rhinoceraptor]

I haven't seen any convincing evidence that significant muscle loss occurs with a 7 day fast. If you get a DEXA scan before and after, you will have lost a lot of "lean body mass" and your muscles will be smaller, but it's only because you lose about 5-10lbs of water weight.

The only major health risk is refeeding syndrome, and even then it's only really notable if you're an alcoholic or have anorexia. If you're otherwise healthy with normal sodium/potassium/etc. intake and you take it slow when refeeding, I don't think it's particularly dangerous. Obviously, talk to your doctor, and it's probably good to get blood work before doing something like this.

[TimSchumann]

I lost zero noticeable lean muscle mass on my 60 day fast, at least no more than I would have sitting on the couch doing nothing.

There's just not a metabolic pathway for breaking down muscle/organ tissue for energy when you have adequate fat stores. We would have died off as a species a long time ago if that were the case.

In the grand scheme of things, if you have the body fat, 7 days is nothing for a fast.

Edit: To those asking, yes. I fasted for 60 days, water and electrolytes, no calories.

[CamelRocketFish]

When you say 60 day fast, are you saying you didn’t eat for 60 days and just drank water?

[brodouevencode]

https://news.ycombinator.com/item?id=27619297

I remember his post from a few months back - found it rather inspiring.

[pid-1]

Did you exercise or work during this period?

[TimSchumann]

Once-ish a week there was Light lifting, think moving a whole trees worth of firewood or a light day on a family farm.

Quite frequently I hit over 10k steps/day on my step tracker, sometimes double that. I live in the middle of a major city and walk everywhere, and this was before work from home.

If you’re looking for exercise/fasting advice check out my fat per unit time post elsewhere in this thread.

[sedivy94]

Thought experiment...

Humans have weathered long durations of food insecurity for much of their existence. If the default metabolic solution to fasting was harvesting energy from skeletal muscle and smooth muscle... well that strategy wouldn't work for very long, would it? The lowest hanging fruit is muscle/liver glycogen, and fat mass after that.

Breaking down proteins (gluconeogenesis) is a metabolically expensive process, requiring large energy input for low energy output. The body is wholly invested in protecting these vital organs. Skeletal muscle has a reputation for being fickle, subject to change based on stimulus and energy demands, but those adjustments are most significant and relevant to those who are invested in maximizing lean mass (athletes, bodybuilders, statistical outliers).

Fasting is relatively protein-sparing, all things considered. The observations of apparent muscle loss can be attributed to loss of muscle turgidity - a reduction in glycogen, intracellular fluid, and electrolytes. The difference between fed and fasted states, both visual and internal perceptions, are quite extreme.

Are extended fasts ideal, or even generally recommended, for someone with the singular goal of building muscle? Absolutely not. But it is a flexible tool when goals shift towards catabolic outcomes (losing weight). Furthermore, the downstream benefits of fasting can translate to improvements in insulin sensitivity, nutrient partitioning, muscle-building, and body composition... which are relevant to anabolic outcomes.

[SapporoChris]

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2495396/

"A 27-year-old male patient fasted under supervision for 382 days and has subsequently maintained his normal weight."

By comparison 7 days is trivial. More to the point, a 7 day fast with medical supervision should be safe, if it is not, the supervisor will advise against it.

[femiagbabiaka]

Not to be snarky, but reading the linked study would be helpful here. Your body is quite intelligent when it comes to drawing on its energy reserves.

[brodouevencode]

This is a damned-if-you-do-damned-if-you-dont situation. If OP says you should fast and someone gets hurt, that's bad. If OP says you shouldn't fast then what gains could have been made in that lost time.

A better way of looking at it is to take it incrementally

* skipping breakfast

* skipping breakfast and lunch

* skipping a whole day

* eating one meal every two days

* eating one meal every three days

* ...you get the point...

I don't think OP would advocate just jumping right into it. Start small, work up from there, listen to your body. You wouldn't jump right into running a full marathon.

[TimSchumann]

Exactly right, to all of this advice.

I believe I say multiple times in this thread nobody should just jump in and do 60 days, however I believe anyone (caveat-ed up thread) can 'jump in' and do 7 days at any point in their life.

It won't be easy, it'll be especially hard if you've never fasted before and are on a standard diet, but it won't be dangerous. It'll just probably be the most difficult physical and mental thing you've ever done.

Also, thanks for linking to my spreadsheet up there.

[lm28469]

> I'm not sure if starting something like a 7-day fast without medical supervision is a good idea

I'm not sure starting a western diet without medical supervision is a better idea given 75% of the west is overweight or obese. Unless you have medical conditions a 7 days fast is a walk in the park in term of health

[m348e912]

You bring up some interesting points. I've dabbled with fasting in the past and it seems to be relatively safe and beneficial up to 10 days but there are two mistakes I see people make.

Mistake 1: Drinking pure water. Your body does need some specific minerals even when fasting. Cole Robinson, a fasting focused youtuber (who is not for everyone), has shared a Magnesium, Sodium, Potassium, Sodium Bicarbonate & Water recipe he calls Snake Juice that keeps electrolytes steady during a fast.

Mistake 2: Drinking liquids that break the fast. I've watched youtube videos of fasters add things like diet soda, gatorade, and even jello to their fast. That defeats the whole purpose and negates any positive effect.

[godshatter]

Diet sodas get a bad rap and for good reason, but I've been unable to stick with anything other than diet soda long term (though I've tried multiple times). I know that diet sodas can spike blood sugar in some people, but it doesn't break me out of ketosis when fasting. YMMV.

[m348e912]

Just my perspective, but I think diet soda certainly breaks a fast. I can see how it could potentially not affect ketosis, but as far as fasting goes, water & minerals are truly the way to go. I will also concede a true "water" fast makes the fast much harder, although I think that's part of the experience. It's not supposed to be easy.

[HanMei_333]

> The crazy thing is, if you can get to 7 days, anything past that is just mental and you can go as long as you have the body fat to sustain the fast,

It's not that easy. You have to properly substitute electrolytes - sodium, potassium and magnesium. And that is almost impossible without small doses of carbs.

My longest fasting was 42 days. I did 28 days three times before. I'm fasting more or less regularly (once per year) for about 25 years.

Don't do very long fasting without guidance of a doctor. Your heart needs properly balanced electrolytes.

EDIT: I've just seen your other comments here also underlining the need of electrolytes. I still leave my comment here for the other readers ...

[michaelbrave]

I would say there are some things to watch for if doing long term fasts, one is salt and potassium levels to prevent heart attacks, especailly true for those of us who are on the larger side, and especially as one get's closer to say the 20 day mark. A week or two probably wouldn't kill anyone if they have the fat stores, but a heart attack prompted by lack of salts is a potential concern.

[moonchrome]

>It's such a shame that there isn't more research in this area.

From what I've seen there is actually research into it and the weight loss/fitness benefits don't seem to be any better than any other calorie restriction when equating calories (slightly worse for muscle mass when combined with exercise in one study IIRC), and other claims seem overblown.

Layne Norton has a couple of good study reviews (eg. https://www.youtube.com/watch?v=0PyBoKSv2tI)

[warble]

You're right, the weight loss per calorie restricted is about the same. That's not the point, it's about feeling better, being healthier and for IF, the lifestyle makes it easier to manage your sugar intake, calorie intake and overall health.

[moonchrome]

Sure, but I think there were some studies that looked at adherence and it didn't seem different to other diets there as well - but I could be misremembering.

That being said - this is highly individual stuff - even if something doesn't work for 99% of people - it doesn't matter if it works for you - and it's easy to try.

It's just important to have realistic expectations about these things, because overhyping tends to lead to motivation spikes - you get enthusiastic and then you get disappointed and crash to 0.

[hi41]

I have tried fasting by skipping breakfast and I have mostly failed because I am unable to endure when hunger strikes. I am interested to learn the mental methods you use to over that struggle.

[msandford]

You have to wrap your brain around the idea that hunger isn't pain to be avoided but a natural feeling that comes in waves. It's not you that's hungry, it's your gut microbes and they can be annoying but they don't really hurt you. Hunger is the sensation that one has when some of their gut microbes are running out of food an experiencing stress.

I recently did a significant amount of caloric restriction, from probably 2500/day down to more like 1500/day. The first day was awful. The second day wasn't so bad. By the fourth day this new amount of calories feels fine. I had to give myself permission to do basically nothing for several days though because I just didn't have it in me.

[brodouevencode]

It's been pretty simple for me: just get busy. Wake up, get ready for work, and go. It's tough with kids though because we make them breakfast here and the temptation is real but if I put time boundaries on myself (up at 6, out the door at 6:30) then the fake stress forces me to get out the door. Once I'm on my way to work I really don't think about it. The only thing I consume before lunch is black coffee, and that seems to fix any hunger pangs.

[nameless_me]

This. Coffee with a teaspoon of coconut oil or butter if preferred. The oil increases satiation (feeling full). Then get at it.

Whatever you need to do or narrative to tell yourself why you don't need to eat, do it. Keep busy, work, clean the house or volunteer. By keeping occupied, the mind will not seek food out of boredom and ritual.

Eat once a day. Typically I "reward" myself with the evening meal after fasting through the day. There are different kinds of fasts but the one which seems to work best for me is 1-big-meal a day type fast. The rest of the day, I can drink water or black coffee.

[hsn915]

This is what helped me - your milage may vary.

1) Remove from your mind the idea that huner is suffering. It's all in your head. It's merely a mild discomfort.

If you ate last night and woke up in the morning, you are not hungry. You are just used to eat in the morning. Your body will not suffer any thing from skipping breakfast. It alerady has more than enough energy storage. It was designed to tap into it.

2) Surround yourself in a virtual environment where fasting and accepting hunger is the norm and expcted and obvious thing to do.

Read blogs about fasting. Watch youtube videos about fasting. Read books about fasting. Watch how people who consistently fast are healthy and fit.

3) Understand that there are two types of pleasure. Fleeting pleasures, and lasting pleasures. The fleeting pleasure are the sensual. They are momentary and quickly go away. If you spend your life chasing fleeting pleasures, you will be miserable.

Lasting pleasures - if you can call them so - are mental states. Contentment. Feeling in control of your life. These don't come from things. They come from what you value and the way you conduct yourself in the world. If you have no value, you will be controlled by your desires.

Some people think this is freedom: to do whatever you desire. To me, it's slavery. Because when you follow this path your life will be miserable.

Some people try to cheat by pretending that their misery is actually happiness. You see it in the people who insist that fat is healthy and beautfil and hot!

4) Understand that your mind is distributed. Even if you resolve to fasting, there will be some component of your mind that really really wants to just keep eating. Sometimes it might come out and win. Accept that such a thing could happen. When it does happen, don't be too hard on yoruself. Try to understand why it's happening. But anyway, go back right away. Understand that many other components of your mind want to continue doing the right thing.

[godshatter]

One small thing I learned is that a lot of what I thought was hunger was actually thirst. I have been eating one meal a day (with some exceptions) for the past 3 or 4 years. If you're hungry during a fast, drink something. This will put something in your stomach and that helps and then after a bit the hunger goes away if you ignore it long enough. When fasting you need to up your fluid intake anyway.

[chrisux]

The biggest thing that helped me aside from trying to change my mindset, is black coffee and black tea without anything added. Coffee in particular seems to have a hunger suppressant quality and helps with perceived energy loss, but black tea seems to do the same for me. Whenever I am feeling hungry I just drink tea or coffee. There are so few calories involved that I believe it doesn't break a fasting state. Some may consider it breaking the rule, IDK.

[winrid]

Caffeine in general is a hunger suppressant. Many weight loss pills wil have caffeine added.