I have fasted 100 lbs away over the last 2 years. I adhere to an 18/6 time delay eating schedule but have done 2-3 day fasts with 1 refeed meal for a month at a time. I've also done countless 5-7 day fasts. I've gone as long as 12 days with nothing but water. There were many months where I could count the number of times I ate on one hand. My last go was every other day with just one meal on my eating days. I did that this year for all of January to the end of March and would never recommend alternate day fasting to anyone. You will mess your self and your metabolism up. You will lose a lot of muscle. Alternate day fasting should be avoided.
Never over two years did I feel any of the mental clarity or more energy you speak of. I follow guys like Cole (snake diet) and even he speaks of the feeling of dying and lying in bed shivering on a 5-7 day.
Are you sure about the metal clarity and energy levels, because I and the folks I know who fast don't seem to have those affects.
> I've gone as long as 12 days with nothing but water.
This is dangerous and please don't encourage others to do only water fast.
Pure water fast is dangerous beyond 4 days or so.
You need to supplement minerals while on per-longed fast.
Salt, magnesium and potassium are vital to regulatory processes in your body.
When your body uses up all reserves it will not be able to sustain those processes. It is serious business so please read up on the subject while trying anything longer than 3 days.
> feeling of dying and lying in bed shivering on a 5-7 day.
This is body telling you something is wrong, ignoring is outright stupid. Like ignoring that you are bleeding.
I remember reading about someone who fasted for an entire year. Of course he was morbidly obese when he started, he took supplements, and he was under strict medical supervision for the duration of the fast. (Sorry, don't remember the source.)
"Starting in June 1965, Scottish man Angus Barbieri (1939 – 7 September 1990) fasted for 382 days. He lived on tea, coffee, soda water and vitamins, living at home in Tayport, Scotland, and frequently visiting Maryfield Hospital for medical evaluation. He lost 276 pounds (125 kg) and set a record for the length of a fast."
Interesting. Any studies that validate the first point? I recall research talking about how there’s little muscle wastage until day 21 in normal healthy adults.
Keen to know if we have learned more in this space
The figure I have seen is that muscle wasting drops to less than 0.2 kg per day once the body fully enter ketosis.
Obviously, anyone considering a fast longer than a few days should do so under the supervision of a doctor who can monitor electrolyte levels etc. They can also check for the rare enzyme defect called Medium-chain acyl-CoA dehydrogenase deficiency, those with it are unable to fast safely.
I agree, a 12 day fast is dangerous and unnecessary. I was experimenting and would never do it again. Anything longer than a 3 day fast (72 hours) is not necessary.
If you supplement minerals and listen to you body response, then you can fast as long as you have fat stores in your body.
Its only dangerous if you don't know what you are doing or ignoring signals from your body. Lightheadedness is common thing people report or /r/fasting/ and almost always they don't take salt while fasting.
But I am not an expert, it feels like I have done more reading about fasting then actual fasting. So don't take advice from strangers (especially /r/fasting or worse dryfasting nutcases).
We need different words, really. You're describing a starvation or calorie reduction fast. More common, and what I practice, is more like a time-shift fast. For example, I exercise in the morning before eating breakfast. This is a fasted state. It trains your body to use fat as fuel. The eventual result of doing this is greater stability in your mood & mind. Your body doesn't crave carbs so much anymore, and you feel good whether or not you've eaten recently.
Your brain runs on carbs. The easiest source of carbs is carb rich food. This is why hangry people seem to want nothing but cookies & candy IMO. But your body can only hold a limited amount of free carbs at any time. Meanwhile, your liver can convert fat to carbs to feed your brain, and your body can hold a virtually unlimited amount of fat. This pathway is more difficult, so you have to train your body to use it.
So I don't think it makes you smarter or more energetic. But it does make you more stable & help avoid the crash.
Not OP, but I agree with you that we need different words. Because what OP is doing is not starvation (till their body is actually wasting away). Having done a few 3 days fasts myself, I can attest to feeling a euphoric energy around day 2 where I felt lighter, and sharper. I have been told it isn't universal, but from the content I have been consuming it has something to do with brain switching to consuming ketones.
Which actually brings me to another point; the brain does not run exclusively on carbs (glucose) - it absolutely has the ability to (and does) functions well on ketones. This is why ketogenic diets can work for many people.
But yes, there's lots of bio-chemical mechanisms that get kicked off when you're fasting for an extended period, so it could be something else that's unique to the people who experience the euphoria.
I am not sure if you've come across this concept, but "Metabolic Flexibility" seems to be trying to explain some of the "after burner" affects of switching around my dieting habits. Where I am no longer exercising strict caloric restrictions, or fasting on a regimen, but I am still observing some of the benefits of when I switched over. (Less bloating, more energetic even after a large meal, less voracious appetite on normal days).
Not eating for few days - is not (yet) starvation, its not 'body wasting away'.
Its a state where your body and mind need to be the sharpest in order to catch food. Or else due to lack of fuel you will enter actual starvation (no fat reserves).
When you have reduced calories intake ~~500kcal a day you are signaling to your body that you can find/catch food but there is not a lot of it. Your metabolism will slow down in order to adjust to reduce calories. You loose muscle mass much faster than when not eating at all.
I have done multiple >3 days fasts and I havent experienced this sharpness feeling though. It seems some people do and some don't.
Also worth mentioning keto is natural diet of Eskimo people, they survived generations eating seal's meat and fat. So keto is not some crazy nutjob diet invention of 21st cent.
My understanding (and experience) is that this clarity is usually just about the lack of all the crap that normally makes you feel awful. Things like sugar, dairy, and processed grains plus preprocessed foods. I've always found that after 10 days, you start to feel amazing and do so for around two weeks more before your body starts to adjust.
The mental clarity comes from adrenaline. When you fast your body slowly uses up its glycogen store and releases adrenaline to compensate. Presumably it does so in order to keep you active / motivated enough to go look for food to refill your glycogen stores. It is this adrenaline that gives you the mental clarity and causes you to have trouble sleeping when on a fast: fasting is essentially natural adderall.
On top of this, once you use up all your glycogen, your body enters a period of autophagy which causes disfunctioning cells and protein fragments to become broken down and reused. This causes your body to function more efficiently, including your brain.
That's true but it's also true that neurogenesis will start at some point during a fast. For me, it's around day 3 or 4. It's an evolutionary mechanism to form new connections in the brain to help find food/survive.
When I fasted I remember the feeling of energy kicking in around day 2-3. I had moments of supreme clarity but also moments of fuzziness. The energy boost was real though. I continued to exercise quite heavily so didn't't see any muscle loss. I'm quite a big guy so there were a lot of fat reserves to melt—my skin became very greasy as if I'd eaten a very fat-heavy meal, I could even taste the oil in my mouth.
I wonder if, if you are not a big eater, then the difference might be less than if you tended to be full of food, digesting away all day and night. Similarly, if there's not a lot of fat on you maybe, rather than burning fat with an energy boost, you end up burning muscle and feel tired?
I’ve never done the long term fasts, but my anecdotal experience also confirms this - I definitely have significantly less mental clarity on any type of fast I’ve done, to the point where it definitely affects my productivity even by end of day 1.
Myself as well. You just hit low blood sugar. Technically not fasting, but I have an appetite so weak I can skip meals easily and will do so if I don’t pay attention. Eventually I just feel very lethargic and enter what I can only conceive of as “starvation” or “energy conservation” mode. It’s not pleasant. I also have trouble with muscular mass being the first thing to go.
I think I also just become more irritable if it's been too long since the last time I ate. It definitely doesn't seem to improve mental acuity for me, and any kind of physical activity is just going to feel worse. I've never tried any kind of a formal fast, though, so I don't know if there's something to planned schedules that makes it different.
I can kind of see how I might, under some circumstances, enter some kind of a state of quicker thinking after fasting, but I think it would be something similar to sleep deprivation, where you get perhaps a bit "hyper". That's not really a state I necessarily strive for either.
I've also never been overweight, and have always had more trouble gaining weight than getting rid of it. I wonder if that has something to do with it. I suppose the metabolism might be different if you've got some fat stores vs. if you're rather low-fat.
I can understand how fasting could e.g. have differential effects on cancer cells and thus be useful in specific circumstances. I also understand that people have rather different reactions, so I don't doubt that some people achieve some kind of a state that feels good or useful by fasting. But I don't really understand the hype, or calling it a panacea.
I start to get this clarity and energy around the 24 hour mark. It is unmistakable.
Each time I hit that point I get the clarity and energy, and remember that it happens each time. Pretty interesting. So much energy I can't sleep and end up eating when I can't sleep which breaks the fast.
I am only 5kgs over weight at this point if that is relevant for anyone.
Many, many people who follow fasting/ketogenic diets report heightened energy and focus, myself included. This usually comes after the carb/keto flu phase once adjusted to the low carb intake and after the body has gone fully into ketosis. You have to be careful to get enough salt while fasting or eating very low-carb, though, as your body can struggle to hold on to water without those carbs you're used to eating. Consuming too little salt can definitely contribute to feeling sluggish.
You don't follow Cole if you don't know the difference between the effects of dry fasting and wet fasting after 5-7 days. If you do know that, you are purposely making a misleading statement to support your argument.
Same here - I've been eating only one meal a day mon-fri for literally years. I also do 2-3 day fasts here and there, my longest was five days. No changes in mental clarity and energy.
I have been on a 18/6 and 20/4 fasting protocol for 3 months now - few up and downs but mostly sticking to it. The obvious results are weight loss (not so much, I'm within my BMI targets). I can confirm that my mental sharpness has improved but it's not the same every day.
Most days I feel amazing, some other days I feel quite tired and I experience some mental fog. I still haven't found the reason for such an oscillation.
I suspect it has to do with what I eat during the eating window (for instance, more sugarish food, more carbs, etc). I think I should record what I eat and compare it with the overall well-being to get to some conclusions.
I noticed that in the winter, eating mostly fruits would cause a “crash” about ~30mins-1h after my fruity meal (but dang I had a lot of energy during that time). When I ate potatoes, spaghetti, I would have a longer span of energy.
I did a 3 day fast to see what it was all about. The energy levels were not there. I would get tired after a short brisk walk. Physically I was weaker but still had burst strength just no endurance or cardio.
Mentally however I found myself unable to have too many variables in my head and my mind was not more able to focus on something but less distracted with extraneous thoughts. I could if I wanted to shut off the chatter in my brain and meditation became very easy.
It is definitely a different mode for me and I do appreciate it but I'm told that many people in my family have ADD and that I might actually be showing symptoms that would go away when in ketosis.
I don't think that a sudden 3 days fast will bring any immediate benefits (perhaps some weight loss), on the contrary. I see fasting more as a long term, life choice. I do feel more energetic and sharp during fasting.
I recently did a full check-up (I'm 48) and all my blood/urine values were spot on - before starting my fasting protocol some values mostly related to arteriosclerosis were slightly over the recommended values. Obviously, this doesn't say much or it's far from being a scientific proof: it's just an observation. There are good chances that for a lot of people fasting would just not help and make life misearable.
Definitely. I started deopping breakfast. At first it was hell. But you get used to it. Noe I’m down to one meal a day. It’s very convenient, and my energy levels aren’t affected by food intake.
I found my first fast to not be representative of later fasts. You get more accustomed to not eating after you repeat the practice. You become conscious of how often you wander into the kitchen and stick your nose in the refrigerator and the pantry. A cold glass of water becomes a delightful snack.
You might try reducing your fasts to just 24 or 36 hours on weekends.
Currently, I do intermittent fasting where I don't eat before noon or after 6pm, 7 days a week. It helps me to manage my weight, I feel consistently energetic (I work out most days, cardio and weights), my mind feels as clear as ever, and I have no trouble following the practice as a lifestyle.
I'd say that I don't feel quite that clarity of thought when meditating after fasting for 30 hours or so. But it strikes the right balance of achieving some benefits of fasting without feeling like a huge chore that I have to overcome.
I had a period a few years back where I did fasts up to 3 days quite frequently.. Once I got used to it they felt pretty good. But, the point I wanted to add is that they would have been very difficult for me if I wasn't also doing a pretty strict low-carb ketosis diet. Without the hunger control of keto and having my body acclimated to using stored fat as a primary energy source, fasts have been untenable.
Did you supplement with any vitamins or electrolytes? I've done a few 100hr fasts and definitely experienced a decrease in physical energy, but my mental clarity was always improved. I have ADD and use a mix of intermittent fasting and alternate-day fasting as one form of my treatment.
Did you try it more than just for that three days (as in, try multiple fasts over time), and or try other variations of it (eg 16/8 intermittent fasting) to see if one of those might suit you better?
I hear people say this a lot, but I've done plenty of fasting and rarely experienced this, and when I did, it was very mild. I don't know if I'm significantly outside the norm. The noticeable difference is that I feel pretty low energy after about ~24 hours of fasting.
Henry Cavill talked about the extreme dehydration he experiences prior to filming a shirtless scene, to make sure there is no water retention, and how he could 'smell water' from across the room.
It makes sense biologically you would get some heightened awareness mixed with periods of extreme lethargy as your body tried to preserve itself.
The resource I've heard recommended most often is "The Complete Guide to Fasting: Heal Your Body Through Intermittent, Alternate-Day, and Extended Fasting" by Fung and Moore. I just checked-out a copy from my library and will be reading it soon.
I felt something a bit similar, that I assume is your brain abandoning the desire for stimulus from food, leading you to go deep into whatever else to feel something. Very nice trick indeed.
i like to persuade people by having them imagine an isolated tiger who hasn't eaten anything in a week. by force of nature their sense of smell, hearing, etc. must all be heightened so as to ensure their survival.
But that's because they are incredibly hungry and food focused, at that point they don't care about taking part in other activities and just want food. That tiger would definitely not be the sort I'd care to be around.
understandably! it will no longer be thinking: human animal, could be dangerous..
but a tiger has evolved to be an apex predator, and not much else.
our predatory speciality is more about leverage than brute force, or scavenging rather than hunting. so i think the logic still applies that cognition can be improved in a way that is beneficial to modern humans. resourcefulness implying that resources are found / conjured when they appeared to be lacking?
Never over two years did I feel any of the mental clarity or more energy you speak of. I follow guys like Cole (snake diet) and even he speaks of the feeling of dying and lying in bed shivering on a 5-7 day.
Are you sure about the metal clarity and energy levels, because I and the folks I know who fast don't seem to have those affects.