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seems to be becoming more and more “scientifically” clear that brains run better on ketones, and burning fat is cleaner for the body
This does appear to be supported by TFA:

> Although the cellular and molecular mechanisms by which IF enhances cognitive and motor performance have not been established, the shift to ketone utilization appears to be one of the key biological mechanisms that prevents age‐related reductions in brain white matter integrity and preserves spatial memory

Sure, though as your quoted indicate, diet is an inexact science at best.

I’d recommend trying interesting diets for yourself, to validate the claimed short run effects.

That's basically the opposite of science.
No, that is LITERALLY science. You come up with hypotheses and test them.

Hypothesis: [Specific diet] will cause no effects on myself, given my unique biochemicalpsycho makeup.

Hypothesis: [Specific diet] will cause [list of benefits/mali] for myself, given my unique biochemicalpsycho makeup.

etc.

Just because it doesn't automatically apply to the population at large does not make it "not science".

Well I imagine what OP meant was that the testing phase in this "science" is not verifiable/repeatable/etc. Perception is an awful way to perform tests, and is very frequently wrong.
That's an interesting point, but I only think it's true under the correct assumptions. If we assume that all bodies are more or less interchangeable, then yes. You'd want to look at large scale, repeatable studies that tie diet into health outcomes, and just follow those.

If, however, there is a large amount of variation among human bodies, large scale objective studies may not hold much value for any particular individual. In that case, the proper bounds of the experiment might be one person, or a small group of similar people. In that case, trying various experimental diets and observing the effects is quite scientific, even if not universal.

> So the brain is happily deriving energy from ketones – sure, but why would this be protective against such a variety of brain diseases?

> One answer may be energy. Despite their superficial differences, many neurological diseases share one major problem – deficient energy production. During metabolic stress, ketones serve as an alternative energy source to maintain normal brain cell metabolism. In fact, BHB (a major ketone) may be an even more efficient fuel than glucose, providing more energy per unit oxygen used. A ketogenic diet also increases the number of mitochondria, so called “energy factories” in brain cells. A recent study found enhanced expression of genes encoding for mitochondrial enzymes and energy metabolism in the hippocampus, a part of the brain important for learning and memory. Hippocampal cells often degenerate in age-related brain diseases, leading to cognitive dysfunction and memory loss. With increased energy reserve, neurons may be able to ward off disease stressors that would usually exhaust and kill the cell.

https://blogs.scientificamerican.com/mind-guest-blog/the-fat...

Wait I might have to dig up the sources. But it is generally accepted in the “Keto sphere” that the brain runs on glucose. Even in ketosis the body creates some glucose for this purpose.
I don't have sources handy, but IIRC the brain will generally to run on about a 60/40 or 70/30 mix of ketones/glucose, but in some experiment they gave people in ketosis a does of insulin to drop their blood sugar to near 0, and they didn't pass out and were otherwise fine.
12 hours? Sounds like just skipping breakfast would constitute as intermittent fasting for me. My breakfast is usually pretty light anyway.
it really doesnt take much to implement an intermittent fasting regimen.

one easy way to hit it is to simply move to an 8 hour feeding window, eg 10-6

really taking advantage of the time you are sleeping as 'fasting' time, makes the concept of fasting a lot less daunting

I try to move that around a bit just to avoid feeling hungry when I go to sleep.
Surely you want hunger hitting when you approach sleep, so you maximise the time you're not conscious of the hunger (because you're asleep)?
I find it difficult to get to sleep if I'm actually hungry when I get into bed.
Generally I've seen 16 hours being the ideal mark for daily fasting.

Purely anecdotal, have not gotten a proper BF-test and don't count calories, but it seems since I started constraining my eating to 8 hour blocks a few months ago that I've gotten visibly leaner to the tune of a couple % points. I lift daily and eat fairly clean with 2-3 cheat meals per week.

You're exactly right. Just skip breakfast and don't eat snacks after dinner and you'll be at 16 hours easy. Try it for a week and see how you feel.

I've been IF'ing for 15 months now and it's great. Lost 20 pounds without even trying and have more energy during the day.

Turns out I IF’d all throughout high school without even knowing it!
this was my realization too when I first started hearing about IF several years back.. "I do this already, but on accident" I have never eaten breakfast in my adult life. I eat once at 11:00AM for lunch, then again at either 6:00PM or 9:00PM for dinner depending on if I train that night or not. I don't snack or drink any calories, so this is basically intermittent fasting right? It seems weird but it does make sense, I am relatively lean and don't put much effort into it.
Yes, this is basically 16:8 (16 hrs without food, 8 hr window for meals)
I'm the same way. People always nag me to eat breakfast but that actually just makes me hungrier and throws off my schedule. Generally if I don't eat anything I won't get hungry for a few hours after waking up, until 11-11:30 like you. I'll have a "big" lunch, like chipotle burrito size, then a light dinner 7-8 hours later. No snacking and stick to drinking water, black coffee, and alcohol. I remain at the same weight I was in high school and haven't fluctuated more than +/- 5 pounds over my entire adult life. It honestly rules and I don't even know how I got into this routine, just that eating breakfast usually seems gross to me.
Yeah, I read through most of the paper, and by their description I can say i've been doing TRF (Time Restricted Fasting) for most of my adult life, and occasionally IF (Infrequent Fasting) i.e the odd day.

I never had time for breakfast, and when I rarely have lunch I usually don't much feel like dinner afterwards. I've never had weight problems (yes i'm >30) but I wonder how one can self determine any of the suggested benefits beyond that... I'm tempted to buy one of those keytone measurement thingies just to see if this is really the case for someone who has never done any different.

[edit]...Thinking back, I do a lot of climbing, and I am surprised some days when I perform really well in spite of skipping eating up until that point in the day - maybe it was actually always an advantage after all as this paper is suggesting. Curious to see if my sends correlate with high keytone levels now :P

What time do you eat and how many times. Did it improve your concentration?
My window is 12:30 to 8:30, so I eat lunch, maybe some snacks in the afternoon, and then dinner. I usually try to get one more snack in right at 8:30, too. No other dietary changes, like high protein or low fat or anything; the lunch, dinner, and snacks are all normal food.

I do find that my concentration has improved in the morning, as I'm not digesting a big breakfast. I start to get a bit hungry around 11:00, but (as you'll read about if poke around the forums and such) it's not a "Ohmigod, I'm going to die!" type of hunger, but more of a "Okay, almost there. Just focus on working for another 90 minutes" hunger that kind of feels good.

Lastly, when people discuss IF, you'll hear a lot of theories about why it works, how it works, what's the best way to IF, including in this thread. But don't try to overthink it, and just try it yourself for a week. Skip breakfast, don't snack after dinner, (optional) go to bed at a reasonable time. If you don't like it, or you're not losing weight[0], then go back to your former routine. Not a big deal.

[0]But I've never heard of anybody not losing at least 1-2 pounds that first week.

I mean... it's literally named "break fast" for a reason!
Like many programmers, especially us older folks, I've struggled with my weight my entire life.

Three weeks ago I went on a ketogenic diet. This week I've added intermittent fasting, only eating between noon and six.

After the "keto flu" period ended, it's been quite enjoyable. The IF comes quite naturally and is painless.

I'm not one to spot diet trends, but my intuition says that keto/IF will be a big thing over the next few years. It feels like it's reached critical mass.

I'd be curious to hear more about what you experienced during your keto flu
There was a bunch of little stuff. I don't think it was as bad as the flu, but it was somewhat uncomfortable.

The initial symptom was wanting to eat all of the time, even if I wasn't hungry. My brain was convinced that I had to spend huge chunks of my time chewing on something flavorful.

So I sliced off some very flavorful cheese and nibbled little tiny pieces during the morning. That seemed to work. Note that I avoided all artificial sweeteners. There's some danger there that I felt I should avoid.

Eating a bunch of cheese leads to constipation. Some fiber every morning fixed that.

There were a few other things. My energy level dropped right off, then came back. Now I have much more energy than when I started. I had a little bit of brain fog, but it was manageable.

The biggest thing I've found about keto is that my personality changes. I am much more relaxed and sedate than I used to be -- more on an even keel. That's not necessarily a benefit. It was just unexpected.

ADD: The crazy thing about keto, as opposed to just IF, is that you have to be really OCD about what you eat. Manufacturers sneak carbs into everything. A food journal was critical for me -- and it was something I felt I didn't have to do, since I already knew so much about nutrition! Good thing my SO talked me into doing one.

> Manufacturers sneak carbs into everything.

It's insane. You go buy beans, and there's rice flour in it. You buy salmon, and there's sugar in it. It's beyond ridiculous, and explains so much about rising levels of obesity. Anything even vaguely processed has a lot of unnecessary carbs added, for one reason or another.

can't upvote this comment enough times!
preach brotha, it really is mind blowing that it's been allowed to get this out of control
I've had it. A few days of very low carb intake leave me feeling very low-energy, foggy, and crabby. It's more of an issue if I'm also too calorie restricted, so if your goal is weight loss, I'd recommend starting Keto first with a similar number of calories to your existing diet, then restricting calories once you're past the adjustment phase.
I had it the first time I switched my diet. Headache, low energy, mild body-ache.

I'm currently a non-strict keto-er, which means I'm really just a high-fat, low carb eater. I think consensus on 'keto-flu' is really just that when you're flushing all the glycogen, it's taking with it a lot of water, and it's upsetting your sodium/potassium levels, I don't really know. I just know that I don't suffer from it when I transition from periods of moderate carbs back to low carbs.

For me it was very similar to the early stages of a bad flu. Tired, headaches, body aches, irritable, and mild nausea for about 5 days. I've heard that MCT oil can ease the transition a bit, but be careful because too much can cause stomach cramps and violent diarrhea. (I've never been able to handle more than one tablespoon at a time.)
Make sure you are getting enough sodium and potassium, its my understanding that being in ketosis increases excretion.
I drink a glass of chicken broth with extra salt every morning to alleviate keto flu symptoms.
I'm 6 weeks into a keto diet, haven't been over 20g of carbs a day throughout. Sleep is much deeper, but I feel I need to sleep longer.

First few weeks (in particular) I had to drop my weight amounts in the gym and found (fighting in) martial arts I tired quicker. Helped this with BCAAs and cream in my coffee prior to exercise (prior to this, my first meal wouldn't be until ~2pm and I'd exercise in the morning fasted). I suspect MCT oil would also help? Also struggled with low blood pressure/headrush when standing up quickly. Helped this with dioralyte and increasing my salt intake. Other than that, it's been good.

Pretty amazing diet really. Far, far leaner, no energy dip in the afternoon, and I'm far less bloated and uncomfortable. Although that's possibly because my diet seems to be a bit more FODMAP friendly. Interesting experiment, either way.

Keto is not exactly compatible with anaerobic exercise. If you're lifting or performing a mix of aerobic and anaerobic (e.g. running / sprinting intervals), your muscles still need some glucose. I'd suggest checking out the cycling ketogenic diet (carb cycling) - it will allow you to refuel your muscles' glycogen stores, allowing anaerobic exercise (weight lifting, etc) while maintaining ketosis 99% of the time (staying lean). Also check out alpha lipoic acid supplements, it will increase the ratio of glucose provided to your muscles vs fat storage during your carb load. Go get ripped :)

Keto and IF can be very dangerous if you don't know what you're doing. I'd suggest getting regular blood testing with your doctor while adjusting and figuring out your routine and meal plans.

It should be over in two days. Carb withdrawl makes you a little more tired. After that, you should even out -- no more crashes and highs -- to a constant level of good focus and energy. You do need to bump your fat and protein intake, first to avoid the addiction eating by actually being full, and second to provide energy. After a couple days you switch to burning fat instead of burning sugars.

See reddit.com/r/keto for help.

Trend: The Silicon Valley execs who don't eat for days: 'It's not dieting, it's biohacking > https://www.theguardian.com/lifeandstyle/2017/sep/04/silicon...
Yep. I had heard the term bio-hacking, heard about Tim F. talking about it, IF, and exogenous ketones, and knew that it was all the rage for some time now. It wasn't really a new idea for me. In addition, I had done what I considered to be "low carb" in the past. It worked great. It just wasn't sustainable for me for various reasons.

What got me started was when random friends and relatives started talking about it. Then I looked around online and found dozens of podcasts, FB rooms, and so forth all sprouting up in the last year or two. The trend is clear. I don't think we've reached the almost-vertical part of the hype cycle yet.

Anecdotally what’s helped me get through the initial crappy feeling of cutting carbs is to eat more fat / protein and stay plenty hydrated. (Plus plenty of sleep.)
I become an asshole when I've cut most or all carbs.

I don't know how to push through that.

Embrace it. Anger and hate burn more calories.
Anecdotally, anger and hate were keys in my diet-soda & coffee based IF diet that helped me lose about 20lb (165->145).

More seriously, my irritability and lightheadedness got alot better after about a week, and it was worth just embracing it until then.

I lol'd, but I did notice (with some dismay, I should probably add) that I really get shit done when I get angry about it.
At risk of going off thread and offering more anecdotal advice, I’ve switched my habits around so I eat carbs at night (mostly berries, vegetables.)

I also do the Saturday cheat day thing.

Let's not lump keto and IF together... IF from what I understand has more substantial as well as proven health benefits (related to stem cells, celluar autophagy, etc.). Whereas keto cannot make the same kind of claims; if you just keep your carbs relatively low you'll probably achieve a similar effect as keto.
Interestingly enough, in obese individuals, usually their adipose tissue cells are packed full of macrophage - it may be possible that keto and intermittent fasting put together are a good strategy for not only preventing the progression of obesity, but also promoting the autophagy of 'sick' fat cells [0]:

• Macrophages play a significant role in regulating adipose tissue functioning during health and disease

• In addition to conventional functions such as clearing cellular debris and participating in tissue immune surveillance, lipid buffering is an important function of ATMs

• Obesity-induced inflammation, characterised by an elevated number of proinflammatory macrophages in adipose tissue, has been suggested to contribute to systemic insulin resistance

> One might hypothesise that the role of macrophages shifts during the progression of obesity from a predominant role in stimulating adipogenesis at the start of adipose tissue expansion to inhibiting adipogenesis once obesity progresses. The observation that adipogenic clusters containing macrophages appear at an early stage of adipose tissue expansion during obesity, yet decline in number upon the progression of obesity, supports this hypothesis. Reduced adipogenesis at later stages of obesity would promote hypertrophy of adipocytes to allow for storage of the excess amounts of lipids entering the adipose tissue, which is in turn linked to metabolic dysfunction such as adipocyte insulin resistance. Indeed, increased adipocyte size has been found to correlate with macrophage presence in obese adipose tissue

[0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4826424/

They kind of go well together though, I definitely find it a lot easier to fast if I'm in ketosis.
It is the same mechanism of action -- the switch of the metabolism to using B-OHB (and other ketones) through the process of ketosis. People have been on a ketogenic diet for a long time to treat epilepsy, and it doesn't seem to have any major downfalls.
Right. Fasting is not a diet. "Keto" (i.e. Ketogenic Diet) is a diet. Both promote ketosis. Keto just promotes ketosis while sustaining life :)
Another Keto person here. I'm eating as much as I want, with no fasting, but strictly keto foods (no carbs).

I lost 10lb my first month (didn't need to lose much), but more importantly for me, my blood pressure is way down from borderline hypertensive 130/90 to 114/77 yesterday. The conventional wisdom is you control 10% of your BP with lifestyle. Low salt and exercise did not touch it, but Keto with the same exercise knocked it down in less than a month.

I'm doing keto too, not for weight loss (heck I could use some weight gain), but to reap some benefits of more stable energy, avoiding carb crashes. I bought some test strips and MCT powder, it took a week to finally reach deep ketosis (according to my test strips). I'm unexpectedly hungry a lot, but I found that coconut milk + MCT oil is very filling.
For what it's worth, since keto strips sort of measure excreted/'underutilized' ketones, you may still be becoming more fat adapted. Also, measuring ketones at night (after a day spent running on them) may be a good time to test.
One thing you have to pay attention to while aiming for a 12+ hour gap is that you don't accidentally consume calories in drinks, especially from sugar... so no milk, honey, or sugar in your tea or coffee. A little sugar calories will prevent the switch flip, leaving you in a starvation state where you feel awful and eat your own muscles.
Folks in the keto/fasting space seem to present salted water as a good option here
Also, bone broth, chicken broth and vegetable broth.
How does that work? Doesn't broth generally have calories?
No it doesn't and I suspect the broth is just to make the salted water taste better.
Fyi, I've heard health professionals, like Rhonda Patrick mentioned here, say that coffee and tea will still cause your digestive system to secrete enzymes that can undo IF effects, that you should only drink water during the no-eat window. I've given up my morning caffeine to do it.
Do you mean during the fasting period or when you are out of the fasting period? Can you consume sugar when you are out of the fasting period?
I’d say that getting adapted to black coffee (I previously took it “light and sweet”) was the hardest part of starting IF for me. Took about 2 weeks, but now I’m enjoying it.
Sounds great, but is this compatible with:

- bodybuilding

- 20 miles daily commute by bicycle

- intellectually intense work, e.g. hackathons

?

(comment deleted)
Yes, you just need to account for that in your total caloric intake. Your re-feeds are going to need to be bigger.
Yes. Your liver glycogen and muscle glycogen will be fine. Your body can convert protein to glucose when it is needed and use ketones for everything else.
you NEVER want your body to convert protein to glucose. it's your body's last resort of energy and is very destructive.
Gluconeogenesis is not the same thing as muscle catabolism.
It really isn't a problem once you're adapted which takes a few days normally (my experience). These guys seem to have no problems with their physical strength on a ketogenic diet: http://www.fatchancerow.org/ - so if this isn't fake (which I don't think) most daily energy demands should be satisfied.
It might be, anecdotally I know of a few high performing athletes who are now keto all the way. That said, it is utterly incompatible with my desire for milkshakes and candy bars, both of which are things I crave at the end of an intense bike ride.
I've done HIIT in a fasted state just fine, and intellectually I actually feel sharper when fasting, which makes some sense. If we couldn't focus our senses while running on stored fat, the human race would have died out a long time ago. There's some data corroborating this, albeit small studies: https://www.ncbi.nlm.nih.gov/pubmed/18779282 https://www.ncbi.nlm.nih.gov/pubmed/7473300
Anecdotally, if I have something important to do and it's before lunch, I'll delay eating as it seems to slow down my thinking. Not exactly evidence, but thinking on an empty stomach seems to work for me.
Lots of people do Ramadan while bodybuilding, playing international level soccer (football) while fasted including no water.
Sounds like some utter bs to me. The guy I know who fasts loses about 20lbs on his bench max every year during that fast.
That's not really fasting in a metabolic sense, though. More like time restricted eating.
Yes. Just increase the number of calories you consume during the feeding window.
Basketball Hall of Famer Hakeem Olajuwon of the Houston Rockets is an observant Muslim; a Reddit post [0] says his game performance dropped a bit during Ramadan, but he still managed to lead the team to two consecutive NBA championships. (Apparently Ramadan never occurred during the playoffs during the years in question.)

[0] https://www.reddit.com/r/nba/comments/3yvhf2/hakeem_olajuwon...

"Sounds great, but is this compatible with"

Yes. I guess I can't speak to "bodybuilding" but I have maintained a high level of powerlifting output for years on a schedule of IF (two 16 and one 24 hour fast per week).

In fact, I would go so far as to say that many activities are enhanced while in the fasted state - my distance running (admittedly short, 4-5 mile runs) feels easier and I feel lighter on my feet and I also feel lighter and quicker in my BJJ practice (even though my weight is the same).

I usually do my heavy weight training while in a (16 hour) fasted state, immediately followed by a high protein, 1000+ calorie meal.

The only adjustment I have had to make is that the meal immediately following my 24 hour fast needs to be contain a lot of fiber. If you shut down your digestion for 24 hours, you don't want to fill yourself back up with cheese pizza or a huge steak.

YMMV.

My longest stretch of keto (and lots of IF) was about a year. I lost around 100lbs. During that time, I rode a bit over 3000 miles on my bicycle, longest ride was 120 miles in a day (purely fueled by keto, coffee, and water - do not do this unless you have supervision by a medical professional). Keto is well known by some ultra-marathoner (insane people) buddies of mine.

Being in the ketosis state is amazing for intellectually intense work.

Regarding bodybuilding, I will copy and paste a reply of mine from another comment:

Keto is not exactly compatible with anaerobic exercise. If you're lifting or performing a mix of aerobic and anaerobic (e.g. running / sprinting intervals), your muscles still need some glucose. I'd suggest checking out the cycling ketogenic diet (carb cycling) - it will allow you to refuel your muscles' glycogen stores, allowing anaerobic exercise (weight lifting, etc) while maintaining ketosis 99% of the time (staying lean). Also check out alpha lipoic acid supplements, it will increase the ratio of glucose provided to your muscles vs fat storage during your carb load. Go get ripped :)

Keto and IF can be very dangerous if you don't know what you're doing. I'd suggest getting regular blood testing with your doctor while adjusting and figuring out your routine and meal plans.

For anyone interested to read about fasting, there is an amazing book written by Arnold Ehret, Mucusless Diet Healing System [1], published in 1922. Interesting fact, the book is from Steve Jobs' reading list.

[1] https://www.amazon.com/Mucusless-Diet-Healing-System-Scienti...

I would be cautious to make health related reading recommendations where the book comes from 1922 and was on a reading list of a man who was rejecting science based medication for his serious sickness until it was too late.
Good point. The problem is that Steve Jobs ignored Ehret’s concept of a “transition diet,” and became taken with the idea of being a fruit-only eater right away.
I thought the problem was that he ignored getting treated for cancer and died?
No way?! How confident are you? Anyways, I mentioned Steve Jobs just as an interesting fact. Nothing more, nothing less. I don't personally believe that anybody should be cautious recommending a book. It's a whole separate topic, but in short, can't help one if he's stupid enough to try whatever is on the internet, but I'm glad to share useful information with the smarter one. Otherwise there is no neither progress nor evolution.
> No way?! How confident are you?

Not just confident, but certain. From Jobs's authorized biography:

To the horror of his friends and wife, Jobs decided not to have surgery to remove the tumor, which was the only accepted medical approach. "I really didn't want them to open up my body, so I tried to see if a few other things would work," he told me years later with a hint of regret. Specifically, he kept to a strict vegan diet, with large quantities of fresh carrot and fruit juices. To that regimen he added acupuncture, a variety of herbal remedies, and occasionally a few other treatments he found on the Internet or by consulting people around the country, including a psychic. For a while he was under the sway of a doctor who operated a natural healing clinic in southern California that stressed the use of organic herbs, juice fasts, frequent bowel cleansings, hydrotherapy, and the expression of all negative feelings.

[...] His friends repeatedly urged him to have surgery and chemotherapy. "Steve talked to me when he was trying to cure himself by eating horseshit and horseshit roots, and I told him he was crazy," Grove recalled. Levinson said that he "pleaded every day" with Jobs and found it "enormously frustrating that I just couldn't connect with him." The fights almost ruined their friendship. "That's not how cancer works," Levinson insisted when Jobs discussed his diet treatments. "You cannot solve this without surgery and blasting it with toxic chemicals." Even the diet doctor Dean Ornish, a pioneer in alternative and nutritional methods of treating diseases, took a long walk with Jobs and insisted that sometimes traditional methods were the right option. "You really need surgery," Ornish told him.

Jobs's obstinacy lasted for nine months after his October 2003 diagnosis. [...] In july 2004 a CAT scan showed that the tumor had grown and possibly spread. It forced him to face reality."

I read the book. It was a sarcastic comment. My point is that the reason why he died doesn't necessarily have to be linked with the Mucusless Diet Healing System, especially knowing that he didn't follow all the recommendations from the said book.

The reason I made my original comment is because the benefits of fasting described in the submission are known for almost 100 years now (to a certain extent) and one may find it interesting to know where the roots are coming from.

> I read the book. It was a sarcastic comment.

Your sarcasm was misplaced. You stated that "the problem is that Steve Jobs ignored Ehret’s concept of a “transition diet,” and became taken with the idea of being a fruit-only eater right away."

That was not the problem at all, as @stevehawk stated and my quote proves. You are pushing a pseudo-scientific book from 100 years ago and mentioned Jobs's name to enhance the recommendation's credibility. Jobs's belief in pseudoscience cost him his life.

> The reason I made my original comment is because the benefits of fasting described in the submission are known for almost 100 years now (to a certain extent) and one may find it interesting to know where the roots are coming from.

And the history of modern chemistry traces back to the days of alchemy; it doesn't mean there is any deeper truth to be discovered by reading alchemy books today.

I was wrong saying "the problem is", whereas what I should have said instead is that he didn't even follow the book, so there is no reason to avoid an interesting read.

> And the history of modern chemistry traces back to the days of alchemy; it doesn't mean there is any deeper truth to be discovered by reading alchemy books today.

You don't need a deeper truth, but be aware why the believed truth is truth, ie seeing the problem from all the angles. You don't know what you don't know.

It would be cool to see measurements of people on Survivor or all the alone in wild shows. Like blood glucose, ketones, movement tracking, and sleep. Maybe even a few IQ and strength tests. There's all this great documentary monitoring and doctors already on site. I assume that academic ethic review boards would never allow a researcher to participate, but it would be great if the shows shared it. Maybe the individual competitors could.

I wish there was some middle ground between self tracking and big expensive studies that don't really change anything.

> The metabolic switch usually occurs between 12 and 36 hours after cessation of food consumption, depending on the liver glycogen content at the beginning of the fast, and on the amount of the individual's energy expenditure/exercise during the fast.

I guess that since my breakfast time is around 8 am, then should stop food intake before 8 pm. The earlier the better. And some light exercise during that period, even better. Let’s do this!.

I highly recommend looking into the work of Dr. Rhonda Patrick, Ph.D. She has extensive material explaining the science behind IF, and many other topics relating to bio pathways and aging.

https://www.youtube.com/watch?v=m6KClPkotxM

https://www.foundmyfitness.com/

And broccoli sprouts! Don't forget the broccoli sprouts!

Jesting aside. She is cool, talks very fast and deliver an awful lot of information in a short time.

Hah gotta get that sulforaphane!

Though I do agree - her podcasts can sometimes be a bit of an information overload for those who aren't biomed folk. However in my opinion, her youtube channel[1] is significantly easier to follow as there are often animations and more lengthly explanations.

[1] https://www.youtube.com/foundmyfitness

And awesome Krill-Oil, too. ;)

Also provided a DNA health check if you want to link your 23andMe account.

What if you have to exercise? Should one exercise while fasting?

Or to put it another way, if you only eat between 10am and 6pm (let's say), what is the best time to exercise? Before work or after work?

You adapt pretty quickly to however you want to setup your fast. The typical recommendation is to workout fasted at the end of your fast, so you can eat afterwards. Have something light to start, then your first full meal shortly afterwards.

I do heavy PPL lifting program 6 days a week and have been doing IF for 3 months. The first 2 weeks were mentally tough at the gym, but after that, the gym really helps me finish off the last couple of hours of my fast and I haven't noticed a negative change in energy levels or strength.

Fitting to see this during this month, as it is currently the holy month of Ramandan for Muslims, who fast from sunrise to sunset for 30 days.
I wonder if any studies have looked at if Muslims who participate in Ramadan receive any measurable health benefits.

Even if Ramadan is only one month of the year, that could still potentially show some benefits if there are any over a whole life time.

The Muslim way of fasting is likely not healthy (or at least not optimally healthy). Food intake should fit the body's circadian rhythm: eat during light hours, fast when it's dark. This is pretty well established.
For perspective’s sake, keep in mind that this practice was established in the desert circa ~600AD and many communities were already much more active during later evening and earlier morning hours. So not exactly the same lifestyle as the modern American person.
Well, perhaps it's good for the metabolism of my muslim colleague, but right now his productivity is way down. Also I don't the ramandan fasting is particularly good since muslims usually eat a lot during the night to compensate.
I generally don’t have a problem at work (Ramadan + Keto). Then again I don’t get up at 2 AM to eat. (Generally have a 18:6 fasting to eating cycle)

Can you share how you are measuring changes in his productivity? I find that, in general, to be fairly difficult to measure, let alone find trends in small time intervals (like a week)

Agreed that binging after fast as compensation is a common trend and not a healthy one. I think the way one practices the fast definitely will lead to differences in productivity. Personally, I work fewer hours but find myself to be more productive for those fewer hours as I have generally prepared better to get work done during those specific times - which isn't something I do for my "normal" workflow.
yeah, but it should be investigated, and there's so many people doing it regularly that it's probably easy to find subjects.

some people do one-day fasting so maybe ramadan has a tangible effect beside psychology

Is your colleague a coffee drinker? It's common for muslims who regularly consume caffeine to go through withdrawal the first week of fasting. This can cause excessive tiredness and headaches. Also during Ramadan its common to make longer prayers at night, which can disrupt sleep.

Personally I just make sure I get enough sleep (even by taking naps during lunch) and taper off caffeine before Ramadan starts, and then I feel just as productive in Ramadan while fasting vs not.

I'm not sure that qualifies as a fast by metabolic standards. Most people fast for 8+ hours every day. By the paper's definition, it's more like time restricted eating.
I believe 16:8 is an IF methodology - You easily hit 16 hours here in Tokyo (2:30 AM -> 6:50 PM)
Right now where I am (SoCal, USA), Fajr (first daily prayer) is around 4:30 and Maghrib (prayer at sundown) is around 7:30. So ~15h fasts this year.

At the same time, Ramadan shifts up the calendar ~12 days every year, so during Winter fasting the days are much much shorter and I agree with what you're saying.

Lol. For years I talk about fasting here on HN and get downvoted to oblivion. Intermittent fasting is what they now say is healthy because it means you're still consuming food so they still make money. A far better alternative and a cure to many many "diseases" (yes, cure, I said it) is a prolonged water fast (10 to 40 days), and/or a dry fast (no food no water) for 2 to 10 days.
I've had serious weight issues for my whole life, primarily due to my love of chocolate. As I approached 400 pounds, I took a hard look at myself and decided to make a change. For the past month (29 days now) I've been doing alternate-day fasting* where I eat about 2000-2500kcal on eat days and cap myself at about 100kcal of half-and-half with coffee on fast days (gotta get that joe).

While a lot of it is no doubt non-lipid mass (glycogen and such), I just passed 30 pounds of mass lost yesterday. After the initial drop from glycogen loss, I've been averaging 0.4-ish pounds a day of mass loss.

A few things I've noticed: What I eat doesn't really affect long-term weight loss. Carbs will cause my weight to rise, but it's definitely just due to the storage and retention of glycogen and water, as I get right back on track with my projections 2-3 days later. However, if I eat carbs and fast the next day, I will get serious hunger pangs. If I eat a mostly keto diet, then I can pass between eat days and fast days with no trouble at all.

My biggest take-away though is that fasting has helped me practice self-denial to the point where I can handle my sweet tooth very easily now. The difference in apparent willpower is so immense that I can hardly believe it myself. I definitely suggest that anyone who has self-control issues with regards to food go on a week of alternate day fasting. Additionally, a fast day is a great way to counter out a day of eating to excess. When I lose my weight, I'll still keep fasting as an option, because it's a remarkably powerful tool.

* It's actually 3 days of fasting, 4 days of eating a week. I do social eating on Fridays and Sundays, so I keep those as fixed eat days, so I just fast on Sat/Mon/Wed, eat on Fri/Sun/Tue/Thu.

kcal is 1000 calories.
Yep. When people say calories in nutrition, they usually mean "kcal".
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Kinda like Mb != MB, cal != Cal, cal != kcal
Yes, but the body needs 2000-2500 kcal per day, not cal.
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For all intents and purposes, when someone says cal they mean kcal. A single actual cal is so ridiculously small it might as well be irrelevant.
Yep. 2000 calories is 2.32 watt hours. 2000 Calories (kcal) is 2.32 kWh. That alone should be enough to clarify the difference, especially if you've ever manually turned a dynamo. Even after energy losses, a person can push a few watt hours into a battery with a hand crank in 10-15 minutes, drastically exceeding the energy output of 2000 calories.
Thank you for sharing your story, keep up the impressive results!
I've had a similar experience when fasting. It also helped to realise that the "hunger" feeling in my stomach is just my body increasing its acidity in preparation for food at its _expected_ meal time. It goes away after a few hours, especially with less carbs in your diet (as you say, bulking on carbs leads to really bad hunger pangs the next day that are hard to ignore).
I just listened to The Obesity Code by Jason Fung and my mind is kinda blown. Everyone you've said matches what the book covers.

The takeaway points are:

- Raised insulin is the key driver in weight by preventing the burning of fat and triggers the storage to fat. Insulin is the hormone that tells allows cells to absorb glucose

- Type 2 diabetes is caused by insulin resistance, which happens over years of prolonged periods of raised insulin without periods of lowered insulin. Carbohydrates and sugar convert to glucose, insulin resistance prevents it being used by cells, triggering the ask for more glucose by those cells to be available, by way of asking for more insulin. Raised insulin and glucose contribute to more fat being stored.

- The western lifestyle is based around eating evenly throughout the day reducing our fasted state. This means our insulin levels don't have a chance to lower.

- Fasting is a way to give your body a break from raised insulin, use up the glucose energy first, then switch to fat burning (Ketosis).

- Sugars and carbohydrates do not trigger the hormone that says we're full when compared.

If this is of interest to you, I highly recommend the book. I'm still learning all the specifics so some of the above may be incorrect.

I very much plan to start reducing my sugar and carbohydrate intake and introduce intermittent fasting.

> Sugars and carbohydrates do not trigger the hormone that says we're full when compared

It's important to note the difference between refined sugars (candy) and natural sugars (fruits). Refined sugars are basically fructose (hello High Fructose Corn Syrup).

Refined sugars -- super hella bad.

When you eat the refined sugars, your liver actually traps the ATP, blocking the pathway to the brain, making you still feel hungry.

Great 10 min clip: https://www.youtube.com/watch?v=8ve6XQH68mg

> Refined sugars are basically fructose

sucrose (white refined sugar) is half fructose, half glucose

https://en.wikipedia.org/wiki/Sucrose

High Fructose Corn Syrup has a variable amount of fructose, but is usually similar to cane sugar because it is used as a substitute.

https://en.wikipedia.org/wiki/High-fructose_corn_syrup

HFCS is generally in the range of 50% to 90% fructose. In other words, it's typically worse than sucrose for you.

Fructose does not provoke a satiety response in the human gastroenteric system, unlike glucose.

So if you do eat candy, prefer sucrose to HFCS and glucose to sucrose. Sucrose will be listed on packaging as "sugar".

I've found that Fountain Soda (in addition to not containing huge amounts of tooth destroying acid) does not make me hungry and does seem to fill me. I've been a single meal a day guy for decades (as well as a soda fan). The switch to Soda Fountains (commercial) and their offensive costing, has kept me in good shape (no visible fat) when paired with continuous fasting.
Thanks for the Great takeaway points from The Obesity Code

> - Raised insulin is the key driver in weight by preventing the burning of fat and triggers the storage to fat. Insulin is the hormone that tells allows cells to absorb glucose

> - Type 2 diabetes is caused by insulin resistance, which happens over years of prolonged periods of raised insulin without periods of lowered insulin. Carbohydrates and sugar convert to glucose, insulin resistance prevents it being used by cells, triggering the ask for more glucose by those cells to be available, by way of asking for more insulin. Raised insulin and glucose contribute to more fat being stored.

> - The western lifestyle is based around eating evenly throughout the day reducing our fasted state. This means our insulin levels don't have a chance to lower.

> - Fasting is a way to give your body a break from raised insulin, use up the glucose energy first, then switch to fat burning (Ketosis).

> - Sugars and carbohydrates do not trigger the hormone that says we're full when compared.

Intermittent fasting was a big part of the early stages of my own climb down from 320+lbs. One thing I will warn about is that, in my case, my body eventually caught up with me and my appetite became uncontrollable again, leading to compulsive eating that I was powerless against until I started taking ephedrine as an appetite suppressant. Don't underestimate the power of a ghrelin/dopamine feedback loop.

Also worth noting: according to my caloric intake log, I now need to eat well under the average to maintain my weight. My understanding is that there is no known way to avoid this kind of metabolic damage when losing large amounts of weight, so you just have to get used to it.

Have you tought starting going a gym. Getting more muscle definitely helps.
I took up rock climbing early on, and in fact that hobby became motivation for losing weight instead of the other way around. I sped a good 6+ hours at the rock climbing gym every week. It was not sufficient to fight the compulsion and I still have to average around 1600kcal/day to maintain.
have you tried low or zero carb diets? I have found that I can much more easily go without eating on a high fat high protein diet.
This matches my experience. I've found that when I'm unable to resist the compulsion to eat, I can at least save on the calories and be better satiated by eating something high-protein rather than the carbs I'm craving.

Not a perfect solution, but it beats the heck out of losing control and bingeing on carbs.

Yes. Believe me, I tried everything.

Also, IIRC, while fat doesn't produce a ghrelin response, protein still does.

This is true. You should limit protein intake to 20 grams in 2hr period to avoid glyconeogenesis, which is the process your body uses to convert protein into glucose. This plus reducing net carbs to 20g or less per day should put you into nutritional ketosis within a week or two. Going keto makes fasting a lot easier. I typically fast between 8pm and noon and find it much much harder when I slip out of keto. If you keep up the program and lift weights (find a good strength program at a gym) your body composition will improve. I managed to get to 8% body fat this way.
I get the impression that people think I'm in search of advice here. I'm about half the bodyweight where I started and have been in this range for years now. I don't know what my body fat % is, but an ultrasound tech called me "skinny" when I was 15lbs up from here so it's probably pretty low.

Keto is like some kind of religion with fitness people. My personal opinion is that people use it as an excuse to eat pounds of steak and bacon while virtue signaling that they're being healthy, but clearly some people really do believe it has helped them and who am I to say otherwise? What I can say, is that I certainly didn't see any of its supposed appetite suppressant effects, and there's a way to get there without becoming some kind of dietary zealot.

Didn't mean to come off as some kind of zealot for keto. For me it's a tool. It has downsides. Your muscles need glycogen to perform at their peak, so you lose strength on keto vs a balanced diet with carbs. Also, I'd never recommend taking the "bacon and cheese" approach to keto. There are much healthier fats to consume and they won't leave you feeling like crap.

Anyhow, was just trying to share some knowledge not give advice. Everyone is different when it comes to preferences but the satiating effects of fat and protein are pretty well studied.

Congratulations on what you have achieved. I have had very similar experiences going from 450lbs+ to 250lbs and counting as a disordered eater. The low carb change had a marked impact on my willpower, among a plethora of benefits, but introducing long term and intermittent fasting took it to another level where I was finally comfortable stating that I am in control after 20 years of battling disordered eating. I am thrilled to read of others getting the same results.
Good on you, buddy!

One trick you might try wrt chocolate in particular: Try darker and darker chocolates. If you can get up to 90% or even 99%, you can get your chocolate hit with little in the way of sugar or calories.

Came here to say this! Dark chocolate satiates, contains very little sugar, and lots of healthy flavonoids.

I've brought lots of the Lindt 99% from my recent visit to Austria :)

> My biggest take-away though is that fasting has helped me practice self-denial to the point where I can handle my sweet tooth very easily now. The difference in apparent willpower is so immense that I can hardly believe it myself.

I also found this to be the case; once you have done it once or twice, subsequent times become easier. To anybody who has tried and given up early: it gets (much) easier.

I have given up all caffeine for Lent twice (three years ago and this last year) and while the first time was misery, the second time was dead easy.

Ketogenic diet and intermittent fasting both give me really good short-term motivation to not snack, too: my most susceptible snacking hours are between dinner and bedtime, but I know that if I'm on a ketogenic diet that eating carbs will erase the "free" 7-8 hours of my body converting lipids to ketones (while I sleep). Similarly if I'm fasting but s/carbs/anything with calories/.

I've found that brushing and flossing my teeth right after dinner to be very helpful. It makes me think twice before snacking because I don't want to have to re-brush and re-floss.

It also seems to improve the outcomes of my dental checkups.

> My biggest take-away though is that fasting has helped me practice self-denial to the point where I can handle my sweet tooth very easily now.

Interesting. One of the benefits I've found from occasional food-abstinence is that I start remembering the distinction between (a) true hunger and (b) craving.

IME (as a male), cravings are almost always for carbs. It takes days of limiting my carb intake for the cravings to subside.

"When I lose my weight, I'll still keep fasting as an option, because it's a remarkably powerful tool."

I strongly encourage you to do this because it will remain helpful to your non-overweight body to not incur all of the extra "mileage" of your ramped up metabolic system, day after day, for the rest of your life.

I would also encourage you to attempt to remove the calories from your coffee on your fasting days - it seems picky since it is just 50 calories but your metabolic processes have to turn themselves all the way on in order to process that energy input. I feel that there is a big difference between all-the-way-off and all-the-way-on in terms of your fasted state.

Best of luck to you!

Would you be up for cutting out sugar for a while? It made a huge difference in my life, no longer crave sweets (chocolate).
Want to see something crazy? This guy has a huge YouTube following and preaches (through obscene language) long fast https://www.youtube.com/channel/UC_yUeH8TsG5pxqvkOxBtsFA. He experiments on himself and "coaches" people on dieting.

Along with the posh attitudes of fad diets can also come extremism. Do go too crazy with fasting!

About 4 years ago I started changing my diet. I drastically reduced foods with sugar and carbs and gradually shifted to a one main meal a day regiment. I eat my main meal (4 eggs, half an avacodo, cucumbers, tomatoes and bell peppers salad with some feta cheese) around 12-2:00. I usually have an apple later. Some weeks I fast for 44-48 hours. I workout at a boxing gym twice a week (about 1.5 hours of a strenuous workout). I’ve been going to the same gym for 10 years, but after changing my diet my stamina increased, sometimes I feel like I can be there all day.

The 44-48 hour fasting are interesting and are hard. Not because of feeling hungry(you’re but for me it’s more mental, the thought of all the food I should eat the next day), but because of other factors. The second night your brain is very alert, almost feeling like consuming a lot of caffeine or other stimuli. So if you wake up middle of the night it’s hard to fall asleep again. In the morning, I’m very hyper again as if I had consumed a lot of caffeine and if I drink tea or rarely coffee just before the end of my fast the effects are greatly magnified. Your brain races like mad. I feel like I have an improved cognitive ability, but I’ve not tested that in any form so it could just be a reflection of being hyper. That said I’ve gotten physically stronger, since my diet change and my fasting. I end my boxing workout with some weights and now I often get comments how strong I am for my body size. And I know I’ve gotten stronger, because the increased reps and weights I can do. There was some research on fasting and how your muscles become more efficient, so I’m not sure if that’s playing a factor or my increased stamina has allowed me to workout longer and that resulted in increased strength. The other factor helping me here I think it’s reduced inflammation. It feels like my muscles recover faster and I have less inflammation problems because of my diet.

Some interesting anecdotes. One of the guys who works for the gym commented at my transformation and said I look like a “jock” now and asked details of my diet. My former boxing instructor who initially told me for best recovery I needed to eat after a hard workout instead of fasting, now has changed his diet as well. So there is something to all these and I’m never going back, but I think we’re still far from knowing the longer term effects of it and also learning about any genetic variability. But I recommend everyone trying it for themselves, it’s easy after the first 7-10 days.

I've been experimenting with water fasting, intermittent fasting, and calorie restriction for over two years with good results. I gradually went from an "obese" BMI to normal, and reduced the symptoms of some medical conditions, especially after 3-5 day water fasts.

I think that if one is going to restrict calories, it's a good idea to eat a high-nutrient diet. Mine is mostly vegan + fish, and based on vegetables, legumes, nuts, seeds, and fruits. Almost zero sugar, low salt, no flour, and not a lot of grains.

A saying that helped me stay focused is, "Food is not a recreational drug."

Please note: dry fasting is incredibly dangerous and one will struggle to find non-crackpot sources that say humans should attempt it for any reason. Healthy people can survive a month or more without food. Without food AND water they last less than a handful of days.
I've never dry fasted and never would. It sounds like a terrible idea.

I try to drink at least three liters of water per day while fasting.

You might be surprised, but most Muslims do dry fasting each year on Ramadan ;)
I've been doing intermittent fasting for about a year--it seems to work for me because I struggle with controlling portion sizes. Mon/Wed of every week I limit caloric intake severely--I skip all meals and snack on olives, pickles, maybe a small amount of avacado in the evening along with a couple of La Croix. Not sure why olives/pickles, other than I wanted to keep the fasting foods keto-friendly. Other than that, I used to chew a lot of gum during fasting, but have since stopped because I'm not sure what exactly "sugar alcohol" is doing to my body.

It has worked out well for me. I started at 230 in June and hit my baseline of low 190's in mid-November. I've been there since doing the 2-day fast. It is not too bad so long as you can stay busy, although it does really affect my mood on those fast days. It has helped my mountain/road biking immensely.

Just wanted to share my experiences...if anyone has other recommendations for fasting days, please share.

I had mood issues with one meal a day regime, I managed to resolve it with Tryptophan supplementation (an amino acid known to act as an antidepressant, avoid if taking SSRIs) for two months and upping my cruciferous vegetable intake significantly (half a kilo a day). This was after reading The Diet Cure by Dr. Julia Ross. I have since stopped taking the Tryptophan and mood remains stable.
How has it effected your biking? More endurance? Peak Power? or just being lighter?
I think it is just being lighter, but the difference in endurance/recovery from hills, etc is pretty significant.
The summary mentions that fasting is used to deplete glycogen stored in the liver.

Doesn't moderate aerobic endurance exercise do the same thing?

If you regularly go on long bike rides, will you get the same benefit?

I can 100% vouch for this, roughly 90 days ago I implemented:

* 16h+ intermittent fasting

* increased exercise (>600kcal Apple Watch active kcal)

* caloric restriction (average of 450kcal deficit).

I lost 20lbs in 90 days (5ft5in 145 -> 125). I've since gone to a full ketogenic diet as an n=1 experiment.

I find the research on this lacking, but fascinating -- its been a very educational experience. Based on the many papers I've read, and talks I've listened to, it seems like society's current ailments of obesity, diabetes, and heart disease (and maybe Alzheimers) tie back to excess carbohydrate consumption leading to hyperinsulinemia.

Re: this paper -- they cite that "Mice fed a high‐fat diet ad libitum develop obesity, elevated plasma glucose, insulin and leptin levels, and impaired glucose tolerance" However, reading the source for that, the diet of those mice was: "18% protein, 61% fat, 21% carbohydrates" -- probably still too many carbs.

Not eating for 16h-18h is not intermittent fasting for me, but how I've lived huge parts of my life. Lunch at noon or soon after, dinner before 8, nothing else. Didn't notice anything remotely pointing towards losing weight to a reasonable weight.
So do we know enough at this point to confidently recommend a fasting schedule that ought to be safe and worthwhile for most adults?

Or are we still bathing in incomplete/flawed studies, bad reporting, and the promotion of diet-fads?

This sounds like something I'd like to try if the reported upsides are real, but I don't have a lot of time to filter out junk science.

It's a pretty easy n=1 trial -- stop eating at 8pm, and eat again at noon. Maybe exercise in the morning to accelerate the glycogen depletion. Try it for a month, report back!

There are many studies on this, the literature seems to suggest it works, and I can say it worked for me.

Anyone read The Hacker's Diet?

http://www.fourmilab.ch/hackdiet/

I find it interesting that he mentioned as kind of a side note that he only eats one meal a day. A man ahead of his time :-)

I'm not at all overweight and personally don't see what this fasting thing is about.

If I even skip breakfast forget hard thinking or strenuous effort.

Fasting is great and all if you don't have to perform mental tasks throughout the day.

When I am on vacation and have time off of work to just relax, I regularly forget to eat, and I barely even notice.

When I'm at work and doing programming, however, even the slightest reduction in my caloric intake schedule results in me feeling lightheaded and "foggy". My ability to code effectively plummets, and I also find myself unintentionally being more irritable towards co-workers.

As such, my job as a professional programmer basically requires me to eat regularly. Fasting is not an option for me, unfortunately.

You could fast before and after work. Eat all the calories you need in your 9 hour window, fast in the remaining hours.
Oh, well, that's basically what I already do. I don't eat at night time (obviously).

There's a reason why the first meal of the day is called "break fast"...