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Features of a successful therapeutic fast of 382 days' duration (1973) (nih.gov)
52 points by ayanai 9 months ago | hide | past | web | favorite | 87 comments

I recently finished a forty day, forty night water fast and while I wouldn't recommend anyone do it, it was effective. At the end I was down roughly 40lbs/18kg, around five of which came back relatively quickly as my body began retaining water.

I supplemented sodium and magnesium during the fast (which is essential), but otherwise only consumed water. During my first few days of re-feeding, I also supplemented sodium diphosphate to avoid hypophosphatemia - which is really only a problem when slamming carbs after an extended fast, but I wanted to be careful.

The most interesting thing for me was that after the first couple days (I've done shorter duration fasts ranging from one to five days intermittently for a few years), my desire to eat was entirely mental - the physical pangs had gone. After about the tenth day I was simply not hungry, at all.

What was the effect on your sleep like? Do you still need your normal 8 hours?

Also could you maintain a normal libido? My wife won't let me do fasts because it impacts our sex life too much. But I wonder if I would break through after a couple days and get things back to normal in that department.

Sleep-wise, it took me some time to fall asleep during the first couple days. After which, my mind calmed considerably and I slept normally for the rest of the fast.

Libido-wise, I couldn't tell you. My sex-drive has been abnormally low for my entire life. Your wife's suspicion would seem to make sense. 'The Science of Fasting' - a movie available on Amazon Prime - goes into some detail about the metabolic changes a body undergoes during the process. It would make sense that reproductive urges would diminish during a time when one's body was focused on conservation.

I recall reading that a consistent 500-calorie deficit (daily) pretty much kills the libido.

I’m assuming you have a lot of extra weight to burn entering the fast.... i weight about 120lb and it seems like a 40 day fast would kill me.

I had recently nudged into the 'obese' BMI category, so yes. From the reading I've done, most Americans/people who eat what could be called a 'Western diet' could fast for 30-40 days before coming close to bottoming out their fat stores.

To put some numbers on this... there's 3500 calories in a pound. If we assume a person burns 2000 calories in a day then a 30 day fast is 60,000 calories or 17 pounds.

The average height of a man in the US is 5'10". The difference between the low end of normal BMI to high end of normal is 132-167, or 35lbs. So even a person at the high end of normal BMI could easily fast for 30 days without going underweight.

This is such a hodge-podge of figures

What adult man burns 2000 Calories a day?

2k calories per day is what the US FDA recommends for the average adult. I found this[0] chart which gives more specific information for age, lifestyle, and gender. After you pick how many calories you likely burn, it's all the same calculations after that.

[0]: https://www.webmd.com/diet/features/estimated-calorie-requir...

So the next recession will be a breeze.

This was very similar to my experience on the 60 day fast I did last summer.

I was stupid/stubborn and didn't supplement anything but salt for the first 30 days. If you're going to fast, sodium, potassium and magnesium are what I would recommend. I could post my before/after pictures and the spreadsheets with my logs if there's any interest.

I'd appreciate getting the spreadsheet, if you don't mind - then I'd know what to track, what to examine. I keep meaning to do this again - I did 2 weeks a few years ago and it helped a lot (e.g. I was sleeping better and was full of energy), but ... life keeps getting in the way.

Great documentation, those of us that are curious do appreciate you sharing.

Does pure fasting have benefits vs consuming a low amount of nourishment, like protein powder with vitamins?

I’ve been doing this inadvertently, due to illness, and lost about the same amount - 40 lbs in less than 2 months. I was trying to eat as much as possible, though. I went from being in the higher healthy range of BMI to the low end.

I'm not a doctor, so I wouldn't be comfortable making any assertions here. If you're interested in the subject, I'd recommend looking up Dr Jason Fung - he's an MD who's been doing work in the area over the last few years.

Thanks, directing me to reading material is perfect. I’m not interested in it personally as I don’t need to lose weight or want to take risks.

Why does it seem to be such a challenge for people to eat & drink whatever they did before - including beer, fast-food and what not - but just less? Too often it's the extreme changes that's being touted about together with some self-punishing training regime that does little good for the goal.

Moderation is psychologically more difficult to adhere to than explicit prohibition. Most drivers routinely exceed the speed limit, but they rarely jump red lights.

Religious laws have lots of "thou shalt not", but rarely any "thou shalt only in moderation". The laws of kashrut are incredibly inconvenient, but they're remarkably easy to follow in practice because they're absolute - either a food is kosher or treif, with no middle ground. You don't have to exercise judgement or restraint, you just have to blindly obey a set of well-documented rules.

Fad diets like paleo are ostensibly irrational, but they're a good fit for human psychology. Counting calories is a minefield - it's too easy to slip up, too easy to deceive yourself about the size of a portion, too easy to nibble at something while you're cooking and forget to count it. A diet that says "don't eat grains" might be theoretically sub-optimal, but it's easy to stick to and much more resistant to self-deception.

Exclusion diets also front-load the burden of self control. If you don't buy any cookies, you have to get into your car and drive to the store if you get a craving for them. If you've got a jar full of cookies, you're relying on pure self control to eat only one rather than scarfing the whole lot. They're always sitting there on the counter, tempting you to break your diet.

Plausible I guess. However, the charade of an extreme regime seems to me to be much easier to fall off and stop caring once the "cheating" begins. Also, I would speculate that an eat-less (calorie-counting if you will) regime prepares one better for the long-term once the goal is reached. Maybe to just internalize the basic idea that it's not what kind of food you eat or how many times per week you're at the gym that matters in the long-run.

This will seem really controversial, but it's the truth, hear me out for a second: You don't get to decide how MUCH you eat! I know this sounds crazy, but it's absolutely true. Every living being whether it's a human or animal takes in precisely the amount of calories that the body says it needs.

here's the mathematical evidence: Over a 30 year period, this intake has to be incredibly precise. In 30 years, you take in about 22 million calories (assuming 2k per day). Now, if you're off by even 5%, say 1m calories then you would gain or loose 300 pounds!! (at the well known 3400 calories per pound) The vast majority of humans and even animals, don't count their calories, so how can they eat exactly the precise amount of calories to be able to sustain roughly the same weight. The reason of course, is because while you may not be counting your calories, your body certainly is, and counting them much more precisely than you or I can. IT adjusts the amount of calories you consume to reach the target weight. Now that target weight is decided by your body's set point - YOU can not change it. If you're body tells you to eat, you must eat. And you can't just trick it by eating a ton of super low calorie spinach.

Now, you may be able to reduce your caloric intake with sheer willpower, for a day or a week, or a month or even a year. But, the body will always be trying to compensate for this. And unlike you, who will grow weary of fighting this war, biological processes don't get tired. They fight and fight just as effectively 1 year later, 5 years later or even 20 years later.

Try this experiment: just once, try to eat half the lunch you ordinarily would eat. I bet you can't do it. Just try it. And if you could do it, you would quickly realize how miserable the rest of your afternoon would be.

Everything we've done: trying to reduce our caloric intake to excessive exercising as far as loosing weight is concerned is sort of a hack. What you really want is to reduce the set point. Once you reduce your set point, loosing weight will be completely effortless. If you look at all the normal sized people, all the epdimelogical studies show: they don't excercise more and they don't eat better, their bodies simply have the correct set point.

> Try this experiment: just once, try to eat half the lunch you ordinarily would eat. I bet you can't do it. Just try it. And if you could do it, you would quickly realize how miserable the rest of your afternoon would be.

I'm sorry but people regularly skip meals and move on with their lives. Am I missing a parody here?

Skipping a meal is easier than eating half a meal. When you begin eating, your appetite increases, making it harder to eat less.

Ok well, I have eaten lunches of varying sizes, so honestly I have no idea why you've presented this as impossible.

I think you make an error by implicitly assuming that calories burned (2k/day) are constant even as the weight is being gained (~300lb/30yrs). I believe that the mass being gained does incur some caloric overhead. So if you begin eating 5% more calories than you should, you'll gain weight, but the rate will slow as the number of calories your body requires approaches the number you're consuming. Therefore you could have a stable weight, while still eating 5% more than you "should" be.

All that said, I do hope someone corrects me if I'm wrong!

Oy Vey...

I'm not saying you're entirely wrong here; in fact, I'd agree with your premise. The issue is, that the entire idea behind consistent dieting and exercise is moving what you'd call the "set point"; but somehow you're railing against that idea in general without giving HOW to change the set point outside of consistent, mindful change.

The general problem with food/caloric intake is that it takes time for your stomach to signal that it's full; so for many people - because most eat quickly - they're actually full well before they know it, which leads to over eating. Your body doesn't "know" its fat stores, it has no way of "remembering" what your current caloric intake/output is; it's a set of feedback mechanisms that tend to handle slow processes better than fast, and the only set-point "memory" that may be involved is the feedback response for the dynamic system sitting around the saddle-points of the equation modeling the process (which is a fancy way of saying any set-point is at best a representation of a representation of a dynamic multi-variate system).

If I proscribed myself to what you're saying here; my "natural" weight gain of roughly 10 lbs per year (from 2007-2013) was because my "set point" is somewhere way, way north of 220lbs (since my weight over time didn't "hockey-stick" level off during any point before then); and once I leveled off it was because I "changed my set-point," which you never explained how to do. Or, based on empirical data, I changed my eating habits, reduced my caloric intake to something manageable for my current metabolic rate, and increased my regular exercise; thus creating a net caloric deficit to get myself to a healthy weight. Once at that healthy weight, maintaining a slower eating pace allowed me to recognize I was full before I was overfull - letting the natural feedback mechanisms actually work.

TL;DR: You're using fancy new-speak to dress up the fact that a 2KCal per day diet doesn't meet everyone's caloric balance sheet needs and people need to be mindful of their own body's needs.

How do you suggest changing the set point?

There is currently, no known way to change the set point, other than extreme measures: bariatric surgery. And even with that, they're not exactly sure how it changes the set point.

We're not even completely sure of what causes the set point to be messed up. There's a mountain of correlational evidence that points to sugar and all the foods that were invented to replace fat (obesity skyrocketed precisly the year US told everyone to switch over from fat to sugar). But, what precisely about sugar is it? the processed foods probably?

At this point, all we can do is try to eat as natural as possible and prevent the set point from ever getting messed up, as early as possible, before your overweight before your an adult, before even childhood. It starts with the baby in the womb.

Everything I have read suggest changing it is quite hard. A study I came across recently was about a 34 year old man who fasted for 40 days, lost about 20kgs. His daily calorie requirements went from like 1800 calories to 1600 (IIRC), but the paper did not go into any detail other than he was able to maintain his reduced weight by eating appropriately for the 6 months after the fast. My recollection of this paper is probably off in some way.

So it seems it is like primarily a combination of psychological and behavioral modifications that impact physiological things. If you maintain the current set point / weight for long enough, your body adjusts.

A new york times article had a study that showed set point remains stubbornly high, even after 6 years of painfully maintaining a lower weight.

I can't see NY articles anymore because i ran out of free ones. but i think it was one of the following two:



A link, if you have it handy? Not arguing, just trying to get more information.

edit: I now recall a UK TV station (BBC? ITV4? sorry) that investigated how people have quite different metabolism - they monitored people with state of the art device showing how they varied quite a lot despite having the same exact diet.

Excuse the bluntness, but given the cocksure manner of the reply I'd assume that you can read about it on his/her site.

I think that if one's goal is to disrupt harmful addictive habits, such an effort can do a fair bit of good.

Yup, in that case, definitely.

Was the goal weight loss?

I would be worried about loss of muscle mass (especially important muscles such as stabiliser muscles), bone loss and cartilage issues. Not even talking about vitamin deficiency and imbalances. I feel that this would wreck my hormone levels too.

It was.

Some muscle loss is inevitable over an extended period of time, but muscle tissue and especially bone tissue aren't storage forms of energy. Fat is.

I definitely felt weaker at the end, but was back to my pre-fast strength level within a few weeks with regular exercise.

I can't assuage your concerns, and I'm not advocating that others do what I did. But, by being careful with electrolyte supplementation and extremely careful when re-feeding, the process was free of negative side effects, for me.

What was your goal?

I read a few days ago about hunger helping with chronic pain and I read a few articles about fasting (although, you're saying you don't feel hungry anymore after a while, which would not be poaitive in my case).

Pretty fascinating stuff, though.

My goal was pretty shallow, honestly: I was going to be looking for a job in the new year, and I wanted to be able to fit into my interview clothes again. I also wanted to move my BMI into the average or low-end of the overweight category.

Re: your interest, there's a segment in a movie called 'The Science of Fasting' available with Amazon Prime streaming which follows a woman undergoing chemotherapy whose doctor ok'd her desire to fast during the process based on promising results from an animal trial[1]. During her first round she fasted and only minimally felt negative effects from the chemo. During her second she ate normally and reported feeling substantially worse. The film also goes into how fasting significantly alters short-term gene expression, which might also be of interest.

I agree that the area is exciting. What little work has been done seems to show that the field holds huge promise for a number of therapeutic uses, the least of which is weight loss.


Thanks, I'll take a look.

Congrats, I think it takes some courage and determination to succeed at fasting for so long!

you're not concerned about longer term metabolic effects?

Not especially. Humans have fasted intentionally and unintentionally for millennia. Our bodies are built for periods of lack.

There is almost no research available on the subject in the west, and there likely won't be - studies of this sort require funding, and Pfizer or whomever aren't going to spend money on research that could show that the most effective form of weight loss available is freely available for everyone.

Right, and part of being built for those "periods of lack" is that our bodies tend to respond to them by slowing our metabolisms. That way when we're well fed again we store an even higher percentage of calories as fat in case of future famines.

The slowing metabolism is a myth.

My weight has been stable in the three months since stopping.

If your base calorie requirements drop because you have lost a bunch of weight, but you don't change your eating behavior after stopping the fast, then of course you will end up gaining the weight back. They have done studies on the "World's Biggest Loser" contestants that show this. The facile interpretation is that you "slowed your metabolism".

That's why you should eat a low fat vegan diet.

You didn't take a multivitamin? How did your body handle lack of vitamin c? or d?

I didn't. Just electrolytes.

I won't say I felt amazing for the duration - I fatigued easily, as could be expected, but other than that and some light-headedness when standing quickly from a seated or reclined position (which is common for people following a keto diet, too), nothing felt seriously off.

>forty night water fast / but otherwise only consumed water.

I don't get it

The supplements were in pill form.

Fasting was a nice tool for me to break my food addiction. I didn't use it specifically to lose weight but to change my mindset around food.

The mindset change for me was basically what I believe most overweight people suffer from: To start eating so much and so often that they forget what 'hunger' really is.

With that change, now knowing for real when I'm hungry and when I just 'want to eat', my weight started to drop naturally, and in 3 years (slow descent, which was good as well for other reasons) I ended up losing 50 kg, going from a "morbidly obese" BMI to a now healthy "slightly overweight" :-)

Losing weight slowly meant 2 good things to me:

1- the mind changed, so now I'm simply unable to get back to that weight, I can't eat so much, all my portion sizes were slashed and I can do that while eating normally - no fad diets or crazy restrictions. yes I eat pizza with a coke sometimes, I just don't eat a whole pizza anymore :) That level of control and balance was what I was striving for, because I think that's durable. I knew I could lose weight by being angry and brute forcing it for 6 months, but I don't believe I'd be able to keep the weight down without a proper mindset break.

2- losing weight slowly also meant I don't have heaps of loose skin, I didn't need plastic surgery or anything and besides still being a bit chubby, I can take my shirt off just fine without getting strange looks :-) I know people that lost the same 50 kg in 6 months through insane diets and overexerting themselves at the gym and their skin just couldn't shrink as fast as they lost weight, they have these folds which usually give away you 'lost too much weight'. I'm proud I don't have these features!

TL;DR: Change your mindset around food, your body will follow. Don't bruteforce it when you're angry, you're just gonna have a temporary weight loss like you probably have and tried countless times if you come from a fat background/upbringing. o/

Why is this a bad idea, supposing you are fat enough to do it?

Because most cannot do it safely. Besides caloric intake, food provides our bodies with a lot of essential nutrients, minerals, vitamins, electrolytes, and even water that our bodies cannot obtain otherwise. Also, over long enough periods, your body will have to start breaking down muscle fibers to provide the amino acids it needs to repair other structures due to wear-and-tear.

To supplement all of that without food is certainly possible, but not easy without a ton of research and a plan. Given that most people cannot stick to a normal reduced-calorie diet, it’s a leap to think that full-on fasting will be possible for the general populous.

That said, I do intermittent fasting all the time, and occasionally do a 24-36 hour fast if I feel I need it. I don’t have an eating disorder, but there are times where my calorie surplus gets away from me during family occasions. The longer fasts help me get back on track, especially in tandem with a hard weightlifting workout at the gym to use that surplus to its fullest potential.

A muslim friend of mine suggested that I fast with her for Ramadan. I only did it for one day, but honestly it was a pretty interesting experience.

I come from a country where skipping a meal is unthinkable and grew up thinking it was unhealthy to not eat when you're supposed to, let alone not eat at all.

During that day I was surprised how "energized" and focused I felt after the initial lunch-time "hump". I reached a point at which I just wasn't hungry any more; I wasn't feeling full of energy but I wasn't tired either, and I was very focused for some reason.

Oh same here. Anytime I tell people I do keto, or IF, they lose their minds. The good thing is that I’ve always done my own thing without regard for what others think (hopefully within reason).

What you found is exactly how I feel daily. By sticking to keto, that loss of focus is minimized as less energy goes to my gut for digestion.

IF makes sense. You will be hungry later whether you eat now or you don't. Keto, I'm not so sure about.

When I did keto, the biggest thing for me was that while I eventually got hungry, it wasn't like one of those "gnawing at your gut" types of hungry. It was very mild. Problem with keto for a lot of people is that they don't consider the problems that a lack of soluble fiber in their diets can cause. I love salads and pickled veggies so it wasn't a big issue for me (I also ate some chia seeds once a day), but others would probably have issues.

> I was very focused for some reason.

Maybe because it was time to hunt... :P

I've been doing IF for almost a year, and I don't consider it a diet anymore. I consider it my new way of life. I was absolutely blown away with the increase in energy I got when I started doing the fasts. I do 3 24 hr fasts a week, and on non-fast days I usually have dinner and either lunch or breakfast.

Simulating the human condition in the post-human world.

Paper clearly cites 5 people died from this before from not doing it safely.

I've read before that you can totally do it, but you need to eat a lot of vitamins and other things that aren't stored in your fat cells and that you usually get through food, to make sure you survive without significant damage.

If, like this guy, you have doctors monitoring you, you'll be okay.

If you just try to go about it without eating, you'll eventually end up with a deficiency in something or other, and have health problems until you eat whatever nutrient it is your missing again.

As I recall the fast itself isn't that dangerous, it's when you start eating again it gets dicey.

Do you recall for what reasons? Fat storage in metabolism?

There's a host of variables in play:


its probably really bad for your kidneys

As compared to clogging your gloms with advanced glycosylated end-products? The routine electrolyte checks indicate his kidneys did fine and electrolyte requirements are fairly straight forward to calculate.

What does "clogging your gloms with advanced glycosylated end-products" mean?

From a quick google search, it seems that cooking generates more AGEs, which are somehow related to diabetes and cardiovascular disease.

The glomerulus in the renal corpuscle is what filters junk in the kidney

You can't live off of just fat.

Also, you are a collection of organisms that work together to keep "you" alive. Punishing your gut bacteria/etc just because you can is not healthy.

> You can't live off of just fat.

He had electrolyte maintenance and periodic monitoring. Fasting is a remarkable component of the cure for all sorts of things.

> Punishing your gut bacteria/etc just because you can is not healthy.

Your gut bacteria don't care. They exit as poop and the remainders will be selected for survival, not "punishment". How does one "punish" bacteria? What does that even mean?

I do not think he was speaking literally, suggesting that the fellow was taking his naughty gut bacteria out and spanking them but rather suggesting that long fasts could disrupt the balance of your gut flora and cause issues when you start a natural diet and start feeding a different ecosystem of bacteria.

How does one "punish" bacteria? What does that even mean?

Let's be charitable. He probably meant that the intestinal fauna population would be greatly impacted. For what it's worth, about half the time I read, "What does that even mean?" I can immediately think of a possible interpretation, and it makes me think the one who asked should have tried at least a little.

And your specific mix of gut bacteria / the ecosystem might be a factor in "making you fat" due to the feedback process between gut bacteria and the brain / hormones. So applying evolutionary pressures to that bacteria might be a good thing.

In the paper they mention he wasn't living off just fat.

Gut flora is not hard to restore, and in fact people have to do it quite often since antibiotics take their toll on it.

You could kiss someone who just vomited and lick an asshole if you want to restore gut bacteria that thrives under a normal diet. No big deal

downvoters: I'm not wrong

> downvoter: I'm not wrong

downvoter isn't either, IMO

I did fast for 5 days once. Also did 2 and 3 days. The most surprising thing is that you get back the sense of smell.

It’s very curious but fasting improves your smell a lot and I am not the only one to observe this phenomenon.

Maybe it’s an old biological mechanism to make it easier to find food? In any case it’s pretty impressive.

I've observed this too

Seems possible it is inflammation related

Can anyone recommend a good book on the subject of fasting? My (admittedly shallow) exploration of the subject tends to lead to pseudoscience/bro science.

Dr Jason Fung's "The Complete Guide to Fasting"

You can get most of the same information from his online output, for free. I found this video especially interesting: https://www.youtube.com/watch?v=tIuj-oMN-Fk

Thanks! This looks like a good start.

Listening to some podcasts that feature Dr Steven Gundry will motivate you to fast for the gut health benefits alone

(Here's one: https://aligntherapy.com/podcast/dr-steven-gundry-plant-para... )

the comments in the health posts on hacker news are always a fun read

We already had the "simple, just lick some vomit afterward" post, so there's really nowhere else for this thread to go.

Are STEAM types on here with undiagnosed mental health disorders legitimizing anorexia nervosa with studies?

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