Science of Fasting
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spyderdoc.substack.com
Growing up sort of poor-ish, I have noticed that a lot of my eating habits are basically not far off Dickensian "Eat now, you might not have anything at all tomorrow" patterns.
Wordly people eats twice a day,
Ascetics eats once a day,
Children and invalids eats throughout the day.
Motivation is never something to overcome. Motivation is power. You work with it.
By "willpower" people usually mean ability to force yourself to do something you aren't motivated to do - you shouldn't try to do that, it's operator error of the human system.
Fear of spiders and snakes were found in infants.
Reflexes are instinctual.
I think we have a few instincts.
The problem with claiming that humans have instincts is that it gives cover for bad theories of mind. For instance, the Nazis believed Jewish people have Jewish minds and German people have German minds; many Marxists have held that bourgeoisie have bourgeois minds. In reality, the human mind is a blank slate, in terms of knowledge and beliefs.
At the lowest point I had lost a lot of interest in food and eating and did not have the same hunger. It is much worse problem since loosing weight is only about discipline, but gaining weight is about more than that.
A different way to look at it would be that a lot of Western people are too sedentary for more than one meal a day. Not only are they getting fat, their muscles are atrophying from lack of activity.
Sedentary people definitely don't need more than one meal a day to survive. It's trivially easy to satisfy daily calorific and nutritional requirements in a single sitting. There are still a lot of people who say breakfast is the most important meal of the day. It is if you are going out to do 4 hours of manual labour in the morning before lunch. Not so much if you only cycle a few miles to work then sit down (and that's already more exercise than most do).
However, I do think there is a difference in how people react to fasting. In particular I think fasting is better for men than for women. I've been fasting regularly for more than 10 years at this point and it's great. But all women I've known to try it have had problems with it.
The idea that we need to eat 3 times a day is from a time most people were living an agricultural life, or doing heavy physical jobs. If you burn a lot of energy, you don't need to be told to eat more.
The idea that we need to eat 5 small meals a day to stay healthy, and never skip a meal! is first world bullshit.
You wont ever starve if your meal is 700kcal one day. You will want to eat more the next day, your head will tell you. Or maybe you want some ice cream after in the same window?
On the other point, very few people who sit around all day need 2000kcal, unless they're relatively huge in any dimension. Either way you will find out if you count for a couple of weeks and if your weight is constant your average intake is your TDEE. If you're sedentary my bet is it's less than 2k.
I feel so much obesity is down to people thinking 2k or even 2500kcal is right for them despite an activity level that means they might be closer to 1500kcal-1800kcal.
Absolutely concur with your advice to count for a couple of weeks, and I'd back that bet...
I'm trying to bulk now and the online calculators I'm using are telling me to take in 3,100 calories, which feels like way too much.
But I am 6'3", 195 lbs, and I'm hitting the gym 5-6 days a week, so maybe?
After years of dieting and weight loss it's hard to eat that much.
But your experience will vary massively depending on how active you are, including how hard you hit the gym.
It's not impossible it's right, but really just count for a few weeks and keep track of your weight, and then adjust up/down up to a few hundred kcal until your weight is changing the way you want it tp.
Unless you're super-lean there's very little reason to add more than 300-400 kcal above maintenance at most (I do less these days) - big bulking cycles take a lot of discipline to break out of. I generally favour slow but steady these days as I'm back into lifting.
Age also factors in - you can expect slower progress the older you get and accordingly you'll need fewer extra calories if you want to avoid adding fat. Conversely, if your testosterone levels and metabolism are at their peak, you might well burn more.
Counting and tracking is really the only thing that will tell you the right numbers for you.
If you have already done this, you will have to enter into a period of building exercise and adding muscle weight back onto your body before your metabolism will work the way it should.
Sure, this is anecdotal but I was eating 1600 calories a day OMAD and my metabolism dropped to burn 1850 calories a day. (As measured by a VO2 Max machine as part of a dexafit scan), which is about 750 calories a day under what it should have been. My standing body temperature was also hovering around 97.3 instead of 98.6
Since then I've been eating more, closer to 3000 calories a day and exercising with heavy lifting 3x a week and my metabolism has come roaring back. I haven't had another VO2 Max scan but my standard morning body temp is now 98.3. In the months I've been doing that I have gained 1 pound, but I am sure a good chunk of that is muscle.
Could have been a psychological illusion, but there you go.
The tricky part for me wasn't getting enough calories, but ensuring I'm getting a good amount and a good variety of nutrients.
I try to eat healthy meals most of the time, but even a handful of "cheat" meals per week to indulge my cravings for tasty, non-healthy food can seriously throw off my overall nutrition profile for the week, since I only get 7 of them.
I've been trying to balance for that by drinking a bottle of Soylent after every unhealthy meal, basically as a nutritional supplement.
When I’m in the office, I crave a sandwich from the pizza place across the street A) because it’s there and B) to kill the monotony of being in my office.
At home I have a far easier time skipping lunch despite there being snacks everywhere.
The main difference its energy levels. Before it was like a roller coaster of 10/10 minutes after eating, then going low to 5 or 4 in a few hours. With fasting, it's more like a consistent 8/10 across the day.
The main challenge with OMAD, it's probably the social aspect, eating it's rarely around calorie consumption.
Bonus: Is practical only having to do clean kitchen utensils and dishes one time per day. Lot of time saved.
Eating one meal a day even breakfast would be considered a 23-1 intermittent fasting schedule or something, but realistically you are in a fed postprandial state for several hours after the meal so there's some daylight between one meal a day and actual 24 hour fasts.
I'm not a fan of CICO but when calories in = 0 and the average TDEE is around 2500 kcal, it's a pretty simple equation. The rule of thumb is 1 kg of body fat is equivalent to 7000 kcal of energy deficit.
There are a few who claim, without any substantiation I can see, that CICO is not the main factor in losing fat, and I’m sure there will be some oddness around the edges which makes this at least not 100% black and white, but yes CICO itself is generally accepted as what all fat loss is driven from.
So back to CICO strategy, because it’s that which nearly everyone struggles with, not CICO in and of itself.
Choosing a strategy that is comfortable enough for a person to sustain is key to long term maintenance of desired body fat level. Some are happy to just eat at a maintenance level through three meals a day, but for many this just makes them miserable and they creep up the calories over time.
Fasting is, for many, a much easier strategy to sustain. Often there is only a small period of hunger in a short fast, but this can even disappear with practice. Fasting can feel great during the fast, and make you feel good when you’re not fasting. CICO is under your control and you’re it even finding it hard. This is why fasting is a great choice for many.
I did a fast which lasted a few weeks (18days) and I could have carried on doing it for longer but I had to break it, I lost 1kg a day. Never felt so good whilst doing it, no hunger.
I think copper supplementation before fasting might help with going into a fast at will. Any nausea from copper is probably Interleukin-2 and its possible, never done chemo, but there might be copper in chemo which will explain the nausea along with the effects of Interleukin-2 which is nausea and fatigue. Copper RDA recently been lowered, controversial, from a cancer prevention perspective.
> Hence doing a workout during fasting gives the best bang for the buck.
Its why the military get recruits up and running before breakfast. The military know how to get people fit fast.
Nicotinic acid on an empty stomach will also cause a spike in a growth hormone. https://nutritionreview.org/2013/08/niacin-cholesterol-wars-...
The more fat in the diet the more the prostaglandin (the sunburn effect flush) & growth hormone response is blunted.
Niacinamide does not give you this effect, only nicotinic acid, both are classed as vitamin B3.
Nicotinic Acid in high doses can also cause abortions reportedly which might be topical for some but something to be aware of.
Also check out Herbet Shelton who was part of something called the Hygienists, he wrote a few books, but his attitude was if the fast kills you then there is nothing medicine could have done for you anyway, controversial but might be true. https://archive.org/stream/fastingcansaveyourlifebyherbertm....
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4684131/
If you get into trouble whilst at Forth Worth or Fort Bragg, they slam you in a tin shack with nothing but water and a multi vitamin to suffer the blazing heat and sweat it out. What do they know?
Supposedly, 15mins in a 80 degreeC sauna sweats more toxins than the kidneys can process in a 24hr period, so perhaps the US mil consider toxins to be the cause of bad behaviour?!?
That seems unlikely.
1kg is 7,700 calories. You'd have to burn about 5,700 calories in exercise, which would be something like a 200km bike ride completed without eating anything.
Maybe a serious athlete who had specifically trained for that could do it for one day, but I don't think anyone could do that for 18 days. For a start, I don't think they'd be fit enough to do it if they had 18kg of excess weight they could lose.
And everybody is different.
2500 is average male adult. That does not mean that he, or anybody else, actually uses 2500 calories per day.
Typically people can burn up to around 39 calories per kilogram of weight. Which means the bigger you are the more you burn.
90kg man, with an active lifestyle, would could need around 3900 calories to just maintain his body weight.
If he was a very large person who is overweight then 150 kg is not going to be very abnormal. I know plenty of guys that weigh like that don't look like fat blobs. They are just really big. Big frames, very tall, etc.
In that case then needing to consume 5500-6000 calories to maintain weight is not unreasonable. It is high, but not outside the expected range.
Short-term fasting might. Long-term, extreme fasting slows metabolism.
> In that case then needing to consume 5500-6000 calories to maintain weight is not unreasonable.
Let's assume that's correct, and the person in question is huge and needs 6,000 calories a day to maintain weight. To lose a kilogram a day you'd still need to eat nothing and do 1,700 calories of exercise a day above baseline to lose a kilogram a day.
You probably wouldn't be able to eat nothing for 18 days, so you'd actually have to burn the equivalent in exercise for whatever you ate.
Let's play with some numbers. Some of the heaviest athletes around are front-row rugby players. 150kg would be right around the top end of that range. If they were on a 50% calorie reduction diet they'd be needing to burn 4,700 calories a day. That's still about 100km of cycling even if you're 150kg. On a very restricted diet. For 18 days in a row.
I believe some Buddhist monks go in for multi-week extreme fasts, but I think they spend their time meditating rather than doing exercise.
By ignoring this CICO concept is not only oversimplifies what is happening in your body, but it is extremely misleading.
When you consume foods you get an insulin response. Insulin response is part of an elaborate chain of reactions that controls how your body regulates the usage of glucose and storage of fat.
Basically:
Your body will metabolize carbohydrates and fructose/sucrose sugars immediately into glucose. It will try to use this glucose as much as possible for fuel for your cells.
However too much glucose can be dangerous. So once your glucose levels in your bloodstream reach a certain level it will trigger your liver to start storing glucose in the liver.
Once the liver is near capacity then it will trigger the glucose to be turned into stored fat.
During that entire process YOU CANNOT BURN STORED FAT.
THAT is the part that CICO ignores.
One of the things that insulin does, along with associated processes and hormones, is inhibit the usage of stored fat for energy. The goal is to regulate glucose in the blood stream and store excess glucose as fat. That can't work if your body is busy consuming fat as energy.
SOo...
If you eat in a continuous manner and keep your insulin levels high then it makes it physically impossible for your body to "burn fat".
In order to lose weight using CICO you need to use up all the calories you consumed, wait long enough for the effects of insulin to wear off, and then start burning through your fat reserves.
It seems like this transition period takes times.
This is what bicyclists often see during races and such things. They load up on carbohydrates for the high energy they provide, but when glucose levels get low they "Bonk Out". That is they lose significant energy.
Where as if your glucose levels were never high to begin with then that can avoid that phenomena.
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One of the major problems with Americans diet is the high concentrated of sugars and complete lack of fiber.
When people consume natural fruits and vegetables high in carbs and sugars then that is mixed in with a lot of fibers. Long chain carbohydrates locked together and difficult to digest.
Which means that in order to get all the sugars out of the mass of the food it needs to be carried into intestines and broken down with the assistance of your gut biome.
Which means that high carb/high sugar foods in their natural state do not release all their calories instantly. It take several hours of digestion to extract everything.
Where as modern diets are full of extremely concentrated forms of carbs and sugars and no vegetable mass to go with it. Corn syrup drinks, concentrated juices, pasta, bread, candy, chips, etc.
These high energy foods are cheap to produce and provide a lot of "filler" in foods and are easily stored and consumed for snaking.
So as a result this style of diet produces the glucose spikes and the resulting "bonking out". Which is experienced by people as periods of acute tiredness, inability to concentrate, and lack of energy.
The easiest way to solve this is by having a quick high carb snack, which then restores the energy levels.
Which means that Americans, in order to maintain glucose levels, tend to eat 8 or 9 or 10 times a day (including snacks).
This not only promotes high calorie intake it also destroys the ability to consume stored fat as energy AND probably contributes heavily to problems like insulin insensitivity.
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This is were one of the major misconceptions of fasting comes from:
During WW2 the USA observed the effects of famine among Europeans. To examine the effect of starvation diets on people the USA Military ran a number of controlled experiments involving volunteer service men.
Some of the effects observed involved intense prolonged hunger, lethargy, etc. Lots of bad effects and negative impacts to organs, various nutritional deficiencies, among other things.
It was then assumed that fasting would result in the same effects as extended starvation diets. And as been treated that way by the medical community for decades.
The trouble is that starvation diets involve regular meals, just very very limited ones. Where as fasting is no food at all.
The way the body reacts to fasting is different.
Why this is happens is theorized to be a survival technique.
Imagine you are a hunter gatherer. It takes significant physical effort to gather food.
If when you cease to eat your body sort of "hunkers down" down to conserve energy then it would potentially lead to a sort of death spiral were less and less food means less and less energy and, thus, less and less ability to get more food. You gradually become weaker and slower as time goes on.
Where what typically happens is after an extended period of not eating your hunger ceases and your energy increases. The idea being that the increase in energy allows to you work harder to hunt/harvest foods.
This is probably why it is becoming more popular for athletes to combine exercise and fasting.
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And all of this, I think, heavily relates to why things like intermittent fasting, paleo diets, and keto diets are popular.
Now I don't believe that a diet of mostly steak and butter is particularly healthy, but I also don't think that a diet of cheap high-carb fiber-free "factory foods" is particularly healthy either.
I think it's likely that a high carb diet combined with moderate fats and proteins can probably be very healthy, provided those carbs come in a more "natural" format combined with significant amount of fiber.
CICO is under your control and you’re it even finding it hard
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CICO is under your control and you’re NOT even finding it hard
Imagine someone sharing their experience with some new climbing gear, and someone else chiming in “All this gear talk is irrelevant, just make sure you take more steps up than down”. What value does such a comment bring?
The OP was sharing with us his experience with fasting. The response was pretty much “your fasting was not relevant. Just the fact that you burned more calories than you consumed.”
F*ck acronyms, BTW
Remember to breathe properly and/or deeper, or incorporate breathing exercises/meditation as part of (water) fasting. The majority of the metabolized fats gets exhaled via your mouth (and tiny amount in sweats/urine) - you do not poop it out. Breathing is very important and often ignored in weight loss. Obviously if you exercise you automatically breathe more, but you might still be taking in swallow breaths. Become aware of your inhale/exhale cycles and focus on releasing the extra store energy on each exhale.
I find not eating throughout the day helps me to maintain stable energy levels and focus. Also, on even on the vlc days I'm not any hungrier because I had a full meal the day before. No hunger pains or cravings at all.
One of the strangest sensations is still pooping 2-3x the next day even though I haven't eaten anything. You quickly realize that all the food you ate takes longer to fully process than you thought.
I usually eat after work and going to the gym. In order to make sure I can still exercise; I just make sure to have some electrolytes in the water I take to my gym and I'm usually fine. Sometimes it gets sketchy on intense days, but if I know it's going to be a hard day in the gym, all I need is about 30-50g of carbs and I'm fine.
My diet still isn't very good. Typical American diet. However, I find it easy to eat high octane foods that used to put me on my ass literally or mentally if I've been "fasting".
Fasting is my favorite way to maintain and lose weight. It's very braindead, time efficient, and cheap once you get used to it. After you become more aware of your bodies hunger sensations and all the habits you have wrapped around food, the biggest thing with "fasting" is making sure you get enough electrolytes.
I've done a few pure water fasts up to a week in duration and a few 2-3 day dry fasts with one four day one. Pure water fasting I tend to be fine for about 4 days and then my energy/focus will start to drop. Dry fasting it happens in about two days.
Technically it's not fasting with the electrolytes. But for weight loss, it doesn't really make a difference.
It's interesting watching science tease out the benefits of very low calories versus very low calories and a restricted eating window. In a weight loss context, I don't think it matters that much really in terms of additional weight loss.
https://www.menshealth.com/fitness/a37508857/intermittent-fa...
I have a theory the body will sacrifice extra fat for its water content.
https://pubmed.ncbi.nlm.nih.gov/14681716/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4901052/
Breakdown products of fat are something like 16% water, but you also need enough water for hydrolysis of triglycerides to get lipolysis going.
I also have a eating window of about 2 hours. It’s super easy to follow on since I never eat breakfast and most days I skip lunch too. The only time I eat lunch of theres a social reason, e.g going out to eat with a college or friend and I don’t want to weird them out by not eating.
I’ve done multiple 2 day water-fasts and my longest fast was 5 days. What you mention about electrolytes is 100% my experience as well, you need to make sure you get enough salt even if that means just drinking plain salt water. Not supplementing 5-10g of salt really makes me feel like shit very quickly during a water fast.
> After you become more aware of your bodies hunger sensations and all the habits you have wrapped around food, the biggest thing with "fasting" is making sure you get enough electrolytes.
This is the big thing that many people don’t understand about how you function when you’re fasting. They think its like a Low Calorie Diet where you end up hungry and low energy all the time, but its strictly the opposite from my experience. Whats super interesting in my mind is this awereness that you also describe of understanding your body more. I can tell if I am hungry just because of the hunger hormone (which has basically no relation to if you actually need food), and if I am actually starving and need to eat because my body is lacking nutrients. It’s subtle but you can actually train yourself to notice this.
I regularly fast (one day every two weeks), and the greatest benefit to me is a more mindful awareness of my gut: I can now tell the difference between feeling hungry because my body expects food and feeling hungry because my body needs it, and can easily decide to delay or skip a meal if I don't really need it. And, more importantly to me, I never feel the need to snack in-between meals.
I'm a thin dude (6'3" and 165lbs). If I don't force myself to eat I will drop towards 155lbs, as has happened before. I eat in a 6-8 hour window daily but I aim for 2000-2500 calories. What would caloric restriction in this context look like?
https://www.calculator.net/bmr-calculator.html
his (assuming a dude) energy expenditure is:
Basal metabolic rate: 1819 cal/day
Sedentary (little or no exercise) 2,183
Exercise 1-3 times/week 2,501
He should not be aiming for "basal metabolic rate".
But considering you are probably in like the <= 3rd percentile of healthy humans in terms of BMI, your 'normal' calories are pretty damn low and probably commensurate with what would be considered calorie restricted.
Basically I don't enjoy being thin but I do want to live to 120. I already do calisthenics and basketball regularly, just wondering what else I could do to min-max my longevity.
My first guess would be that even if there are longevity benefits for calorie restriction, depending what the mechanism is, you could either be already enjoying them by virtue of clearly not eating that much relative to your lifestyle and metabolism, or alternatively that any benefits of starving yourself enough to clamp down on mToR or some other hypothesised mechanism may well be counterproductive by pushing you close to malnutrition or just increasing your risk of injury or whatever.
I guess you could do a self experiment if you were really interested, try a fasting mimicking diet regimen where its five days a month every month to get the benefits of calorie restriction, and see if you can maintain lean mass while getting improvement in markers.
Stay indoors, don't engage in medium to high risk activity, invest all your money into aging research.
This specific commenter could be considered too light for his frame. 165lbs is only 75kg. If anything, eat more and put on muscle.
If anything it kinda sounds like your natural 'set point' already has you calorie restricted insofar as it would.be beneficial
Meals definitely taste better after that window :)
I find I sometimes have like two dinners at 6 and 8 which is interesting…
Today, I do a heart healthy diet, and try to fast from 8PM-12PM (eat between 12PM-8PM). This helps me not eat/snack unhealthily in a condensed period of time.
That said, cholesterol is essential for the production of bile which breaks down foods. Late night foods probably equates to excess cholesterol released to break down said foods and higher cholesterol levels.
We probably want to have periods of fasting in order to not produce excess cholesterol.
So maybe the person fasting had higher cholesterol levels due to his body needing more bile immediately to breakdown a larger amount of food at once? I am very much not a doctor or at all educated in these topics.
And high cholesterol in and off itself is not problematic, if your other stats are in line. E.g. high cholesterol can be a pointer to other problems, but it itself is not considered dangerous.
So did a lot of other people, some of whom were in good shape went on keto, and needed a bypass after not too long.
Total cholesterol isn't necessarily that predictive but non-LDL cholesterol/APOB are strong predictors of CVD
Thanks.
Not sure if this is why but I am also one of those people that can eat super acidic foods all day no problem - I can drink black coffee and follow that up with a bunch of citrus and feel great.
Not that you're wrong having it, just something to realize. Will almost certainly have a negligible or even positive effect on weight loss.
1 large boiled egg is 80 Calories. So like eat 5 or 6 eggs and you haven’t broken your fast??
I had similar habits, was relatively healthy, and rarely if ever suffered from heart burn. But about a year ago, seemingly overnight, I came down with severe acid reflux. I am still managing symptoms to this day.
Not saying it will happen to you, but just raising awareness that human health is a fickle thing and it can take a turn for the worse quickly, often with little to no warning.
On the plus side, I like to try different dishes, as I’m a very curious eater, and now I don’t have to feel guilty when I do.
1 = https://jamanetwork.com/journals/jamainternalmedicine/fullar...
Last time I adhered for 40 or so days I hit the wall hard (approx. -10 kg). Zero energy, and miserable. I wasn't sure if it was electrolytes or if I finally found the keto flu (seems a bit late though, and didn't pass in 3 days). So I abandoned ship and have since had no trouble putting 5 kg of fat back on my body. Time to restart!
Are you testing for the effects of fasting or calorie consumption?
Recent article on the New York Times about this study:
https://www.nejm.org/doi/full/10.1056/NEJMoa2114833
https://www.nytimes.com/2022/04/20/health/time-restricted-di...
The study refers only to restriction in search of weight loss.
Edited to remove one word that may have been perceived as sarcastic.
What I do now is I randomly fast on random days and random times . It’s been more effective for me
Longer fasts (over 16 hours, IIRC) are also catabolic to muscle mass, so they're not even recommended for people who have optimal training plans.
One meal per day is also not enough as only a certain amount of the consumed protein is going to be used for muscle protein synthesis so it's optimal to spread the consumption across multiple meals.
If you lift (and you should!), you should strive for 1.4-1.8g/kg of protein per day, try to hit the leucine threshold per meal (even though this is just a hypothesis!), and use calorie cycling to consume more of the protein around the workout window (anabolic window -- it's not been debunked!!!). Try not to go below 50g fat per day, and do whatever you please as far as carbs go :). I'm personally not a fan of keto as it's too restrictive.
But I was surprised to recently realize how novel a lot of fasting research is, and how unconfirmed a lot of the benefits are. Even the wikipedia page for fasting doesn't have as much as I'd really like to see. It's nice to see posts like this one, but even this doubles down on "there are studies in progress" without any convincing completed studies.
Review studies such as this[0] one basically confirm in so many words that "additional trials are needed" and while IF can help you lose weight "whether IF itself affects cancer-related metabolic and molecular pathways remains unanswered"
It's curiously similar to woo-woo or religious habits and self-help advice: similar in being fringe from the perspective of scientific medicine. But the same groups who I'd expect to be pro-science (for example more likely to get vaccinated) are often mixed up in fasting stuff which isn't (yet) confirmed.
I suppose it's not too unheard of to see tech circles overlap with fringe medicine. Check out r/nootropics for instance. Now, I've experimented with nootropics and various supplements. I don't use the term 'fringe' as a haughty outsider. I'm quite willing to consider that it's "not yet confirmed" protoscience, and that this is different from falsified or counter-indicated "remedies" and bits of fringe medicine, things like homeopathy. But it's curious nonetheless.
[0] https://acsjournals.onlinelibrary.wiley.com/doi/10.3322/caac...
big pharma? government lobbied by big pharma? universities given grants from government lobbied by big pharma?
actually though, the soviets did do serious research into the science/benefits of fasting. Too bad it never really made it to the west.
Watch the video: "The Science of Fasting" for an overview.
Anyway people aren't science we are just people. Everyone has some beliefs and activities that they find valuable for themselves in ways that science can't measure or verify. It's fine.
I realize this could come across as pretty negative or hostile and I really don't intend it that way. I think if anything the problem is that we've sort of constructed a framework where practices are valid only if they are scientifically validated, which incentivizes people to use the jargon of scientific validity to justify practices they find valuable.
Something I find consistently funny about fasting particularly that you kind of pointed out: just because it's new to science doesn't mean it's new to us. I fast for religious reasons, my religion has a fasting tradition going back thousands of years. Its personal spiritual benefits are attested by many over much time and I find it so as well. Good enough for me. The fact that tech nerds just got hyped on it and provoked a bunch of studies in the last decades is fun, but literally a few billion people globally fast for non-scientific non-productivity reasons and will continue to either way.
I do wish science could catch up to some of these old-and-probably-quite-true traditions.
If there's any benefit I can't see it being worth it except in extreme cases. Particularly endurance exercise without calories afterwards is one of the worst things you can do to your day.
If anything it should be the other way around - fasting can be a way to teach yourself to tolerate/control your impulses.
Anecdotally - the more I practice some form of it the more benefits I seem to derive.
Just last month I noticed people dosing off in a long, tedious late afternoon meeting. For me though it just felt boring, but I could easily concentrate and stay focused. Since my only meal for the day is dinner, I’ve forced my body to generate glucose continuously throughout the day, so my brain has enough fuel, and I don’t need to rely on snack and chocolates. No sugar - no insulin spike - no afternoon sleepiness.
I’ve stopped yo-yoing with my wait, as I’m pretty inconsistent with my exercise. It’s a lot simpler for me to force myself not to do something (eat) than to force myself to do something (train).
Not to mention the whole longevity thing that is getting the rounds in the scientific community in recent years.
You lose roughly ~0.75 lbs of body fat at normal fasting levels assuming a reasonably active regular sized person. So how ever many days worth of body fat you would like to gain and lose regularly. You would have to eat back the same amount and probably wouldn't want to gorge yourself too much. A reasonable practical limit might be 5 days.
All of that assumes that you want to maintain a set weight. So the real limit is how much you want to eat in a single sitting. Take those calories and average them across as many days as needed to maintain weight.
Also, the 450 pound (204 kg) man who did not eat for an entire year [0] lost 0.72 pounds / day.
This is also just an evolutionary form of the appeal to antiquity fallacy. I might also point out that we have no clue how early humans apportioned meals throughout the day.
I'm again not trying to say anything about YOU, only cautioning other folks here that the intermittent fasting trend among tech folks looks a lot like social trends among other populations that turned out to be very unhealthy and that people should be cautious.
https://www.youtube.com/watch?v=tWlvWYGztYk
Dr Bernard has some to say on this matter, after his case of the woman who experienced refeeding syndrome and had to be hospitalized.
It's crazy that the best we have are either animal studies or some UCSF study of ~100 people for just 12 weeks. (Very low-power study)
On the science of fasting. It was Ancel Keys whose research, in the 60s, led to the invention of the Mediterranean diet as a way of reducing obesity and heart disease in America. Keys work provided the intellectual justification for the McGovern senate committee, in 1977, to propose radical changes to diet and to government policy. The top-down approach to the national diet led the government to adopt the Low Fat Diet as policy, e.g. the https://en.m.wikipedia.org/wiki/National_School_Lunch_Act
Can you spot 1977 on this obesity chart? https://www.ncbi.nlm.nih.gov/books/NBK19623/figure/chartbook...
Since Keys death, dissenting voices have gotten louder: "In the December 2004 issue of your journal, in his column, Geoffrey Cannon referred to Ancel Keys’ Seven Countries Study and the fact that Keys and his colleagues seemed to have ignored the possibility that Greek Orthodox Christian fasting practices could have influenced the dietary habits of male Cretans in the 1960s. For this reason, we had a personal communication with Professor Christos Aravanis, who was responsible for carrying out and following up the Seven Countries Study in Greece. Professor Aravanis confirmed that, in the 1960s, 60% of the study participants were fasting during the 40 days of Lent, and strictly followed all fasting periods of the church according to the Greek Orthodox Church dietary doctrines. These mainly prescribe the periodic abstention from meat, fish, dairy products, eggs and cheese, as well as abstention from olive oil consumption on certain Wednesdays and Fridays. However, it is indeed the case that this was not noted in the study, and no attempt was made to differentiate between fasters and non-fasters. In our view this was a markable and troublesome omission. The Greek Orthodox Church prescribes almost 180 days of fasting per year. It is unknown to what extent the Cretans who were the original subjects of the Seven Countries Study and who fasted during Lent also followed the precepts of their Church throughout the year, and thus on how many days in total and to what extent the Cretan participants of the Seven Countries Study fasted" https://www.researchgate.net/publication/7530689_The_Seven_C...
The fatal blow to Keys' lipid hypothesis was dealt in 2016 after data from another Keys' experiment was re-examined. "Re-evaluation of the traditional diet-heart hypothesis: analysis of recovered data from Minnesota Coronary Experiment" concludes:
Results – The intervention group had significant reduction in serum cholesterol compared with controls (mean change from baseline −13.8% v −1.0%; P<0.001). Kaplan Meier graphs showed no mortality benefit for the intervention group in the full randomized cohort or for any prespecified subgroup. There was a 22% higher risk of death for each 30 mg/dL (0.78 mmol/L) reduction in serum cholesterol in covariate adjusted Cox regression models (hazard ratio 1.22, 95% confidence interval 1.14 to 1.32; P<0.001). There was no evidence of benefit in the intervention group for coronary atherosclerosis or myocardial infarcts. Systematic review identified five randomized controlled trials for inclusion (n=10 808). In meta-analyses, these cholesterol lowering interventions showed no evidence of benefit on mortality from coronary heart disease (1.13, 0.83 to 1.54) or all cause mortality (1.07, 0.90 to 1.27). Conclusions – Available evidence from randomized controlled trials shows that replacement of saturated fat in the diet with linoleic acid effectively lowers serum cholesterol but does not support the hypothesis that this translates to a lower risk of death from coronary heart disease or all causes. Findings from the Minnesota Coronary Experiment add to growing evidence that incomplete publication has contributed to overestimation of the benefits of replacing saturated fat with vegetable oils rich in linoleic acid." https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4836695/
I can't imagine this was lost in translation.
Any similar nutrition model needs to account for the fact that France, Japan and Korea and have the highest intake of saturated fat, and the longest life expectancy in the world.
possibly less than 14 per week but not for health related reasons