I don't think humans would become too weak to throw spears because they didn't have their Cheerios in the morning.

When I hear people who have skipped a meal complain "my blood sugar is low", I worry for their health. We have fat stores for a reason. Skipping a meal should not be a big deal.

Getting a powerful, accurate shot in itself takes a lot of concentration. But when hunting for sustenance it means getting up before dawn, tracking animals for miles on rough terrain, and managing to approach the animal in complete silence. Once in sight you have to stalk the animal and look for the one perfect opportunity because if you miss or are too loud it will run and you will have to repeat the whole process again. Add in the stress that you and your small group have to be successful or your tribe might go hungry and it's a whole different ballgame then shipping code at the end of the day.

I've never hunted before, but I can't imagine at all that it's a fair fight. Humans have been known to trap them, net them, flank them, shoot them at a distance, lure them, corner them, smoke them out etc. etc.

None of which requires a whiteboard, drafting paper or a calculator.

Are you really going to argue that any human with any semblance of intelligence (and I don't mean deep thought here) would have to risk mauling to hunt for subsistence?

Off topic but some of the best traps are large modern mouse-traps. Just make sure to drill a hole and tie it to a tree with a strong rope so the animal doesn't pull it away. Set it, and you will almost certainly capture a small mammal within a day.

That is such a great point. People have been programmed around the 3 meal regime. I have found it fun to experiment with fewer meals and generally it works fine if I have an primarily protein breakfast I sail through to an early dinner.

That's a hypothesis that afaik no study was able to support (e.g. http://www.webmd.com/diet/features/truth-about-6-meals-day-w... about some studies. I don't have more references right now, but in the past I was looking for a study that supports it, and only found negatives)

> instead, you can also keep to foods which don't spike sugar levels much in general.

Google "bulletproof diet". I think you'll like it.

People are just so unused to being hungry that they freak out when it happens.

I agree that Cheerios are a bad idea generally, but I'm not pro fasting or skipping meals for weight loss. Fat is stored as an emergency reaction to high blood sugar levels, and you get exactly that when eating more between the fasts (you have to). You constantly expose your brain to too much and too low sugar levels, resulting in highs and lows in your ability to focus (and also your mood).

Citation needed. I personally know people who've lost weight long term with quite brief periods of intermittent fasting.

Anecdote alert, but I started doing alternate day fasting after I read the study, then 22 hour a day fasts after I read that people were having results with that. Went from 235 to 185 in 2 years (6' tall, fairly large build.) I'm not strict, and I go off it whenever I'm bored or severely tempted.

I count any drink other than water as a snack, and watch the bread, potatoes, and cornstuffs when I am eating. Who knew it could be this easy? I hadn't really been an overeater for years, I just had never had time to starve.

Yup, I got that and I'm challenging it.

Also, what about tribes that lived in places with cold winters? There are no plants to eat when the ground is covered with snow.

The problem is that people aren't used to accessing their fat stores for energy.

It is my hypothesis that most modern fat stores are not actually energy stores, but rather "toxin" jails (I use "toxin" in the sense of: a substance that the body does not want, possibly because it is harmful, and that takes non-trivial time/effort to metabolize and/or get rid of; think of e.g. mercury).

Which would explain why they aren't being used: In many cases, the body doesn't have a chance to get rid of them because bad stuff keeps coming in.

(You may laugh, but it is not inherently less plausible -- or less supported -- than the idea that fat stores are used exclusively as energy stores).

I have yet to find anyone who has an idea about how it is actually distributed through the body.

Burning fat for energy isn't an idea. As for your hypothesis, hypothesis doesn't mean making up random stuff.

"fat store used exclusive as energy store" IS an idea or hypothesis. One that underlies a lot of other assumptions and theories about nutrition, but is actually known to be wrong -- fat is used for a lot of other things as well (your brain is mostly made of fatty acids, for one; the skin is constantly lubricated with fat for another).

My experience is like the GPs (I only lose muscle if I don't exercise while fasting).

Do you have "nontrivial" muscles? My experience is that I don't lose muscles I use (If I don't jog, I _do_ lose leg muscles; if I'm not boxing or swimming, I _do_ lose arm muscles; but if I do both, and balanced exercises like crunches, squats, etc - I don't seem to lose anything).

For more details i can recommend "Body by Science" by John Little and Doug McGuff.

Or google "muscle recovery time" and read through

That sounds like the sort of pseudo-scientific, unsubstantiated nonsense you hear all the time from New Age healer types. Do you have a source to back up your claim?

p.s: I don't see anyone mentioning toxins before you did

You were the one who started it:

> your body is finally getting rid of some stuff it should have gotten rid of

Sounds like woo-woo toxin theory to me. There are fat-soluble toxins, but I doubt they'd be enough to make you sick or smell bad.

Let me rephrase the question, as apparently it wasn't clear:

Most instances of fasting (specific time + specific instance) do not get acetone breath at all.

Some instances of fasting do get acetone breath, but if they do, it's usually only for a couple of days near the beginning of the fast (usually starting around 2nd day and ending before the 4th day), even if the fast goes on for 3 weeks.

Your explanation does not seem to make this dichotomy possible - it seems to imply an all-or-nothing situation (for a specific instance). Can you extend your description to accommodate this observation? [Note: based on personally collected set of anecdotes - I couldn't find any rigorous collection of this data]

> Sounds like woo-woo toxin theory to me.

I specifically avoided "toxins" in this reply (but not in others) because toxin theory is not well defined, and can thus easily be ridiculed to death. If you define it more properly, (e.g. caffeine "detox"), it is exactly as described, it does make you feel sick. Technically, caffeine is poisonous (as is alcohol) - it's just that in small doses, we as a specie seem to like the effect it produces.

One possible mechanism is that the muscles of the people fasting are more able (either through genes or exercise) to burning fat, meaning that you need to convert less fat into glucose. I'm not a biochemist (I've mainly read Good calories, bad calories plus various primal/low carb blogs) but it seems pretty straightforward (fat -> fatty acids -> acetyl-CoA -> ketones): http://en.wikipedia.org/wiki/Ketosis

Feeling sick on a caffeine detox is likely to just be withdrawal, and/or the "low-carb flu".

I defined it earlier: specific person, at a specific fasting period (by which I meant contiguous period).

> also depends on what you're eating during the fast.

I don't think we're talking about the same thing. "fast" says "what you're eating" is nothing.

You're putting your life at risk from heart attack and kidney and liver failure (and other people's, judging from your comments in this thread).

To quote other people on this thread - "citation needed". I've done this more than once, actually, and I know others who do too.

Yes, I have eaten essentially nothing for three weeks. No, I wasn't putting my life at risk of anything, though you may believe what you want -- did you notice that I'm not the only one who posted about long fasts? You just assumed everyone was eating, but we use "fast" literally, not as a codeword for "calorie restriction".

Although I had the references to support that it's healthy, I did do bloodwork a couple of times through, and at the end, it was -- in fact -- much, much improved. For example, my B12 levels went from -2 sigma to +2 sigma. (If this sounds impossible to you, read the wikipedia entry about B12 - the general "knowledge", even among doctors, about B12 is unbelievably incorrect).

My doctor, who is a reasonably open minded MD, looked at the results and said "just make sure you start eating when you are feeling hungry". That happened 21 days after I started. He wasn't worried after looking at my bloodwork.

If you're healthy at the beginning, irreversible damage starts around day 40 (but is very swift at that point). There are quite a few people in India who do 30 days every year for religious reasons, and suffer no ill effects -- and have been doing this for centuries.

Along these lines, I'm curious what sort of environment you or the other people you know do their long fasts in (i.e. if there is a checklist of sorts).

Actually, no. I'm hopelessly unreligious and unspiritual (or whatever the right adjective for "yogic" is).

> Along these lines, I'm curious what sort of environment you or the other people you know do their long fasts in (i.e. if there is a checklist of sorts).

I know some people who practice it in nature or a retreat of some sort, usually in some "yogic" or equivalent context (i.e. with others doing the same, and usually with a guide)

However, myself (and a couple of friends who followed after witnessing the effects on me) were doing it in the everyday environment, with no special support or anything.

In fact, that first 21-day fast happened accidentally - it was finals time at the university, which meant I spent all of my time studying and exercising (I discovered exercise makes studying much more effective). And then I was feeling really sick for two days (nauseated, congested, tired), and lost my appetite. And then I was well again, but my appetite didn't come back - so I didn't eat. (And those two days were the only days of that month that I didn't spend ~2 hours doing physical exercise)

After 4 days, I was starting to get curious - I was feeling better and better all the time, mildly euphoric even, and yet disgusted at the thought of food. Long story short, within a couple of days I found quite a few trustworthy references that were compatible with what I was going through, and that mentioned that even if I don't feel appetite coming back by day 30, I should eat.

A called my (conventionally trained, though unusually open minded) MD just to be sure, and he said "let's do some bloodwork to negate illnesses (a) (b) and (c) which cause loss of appetite and need treatment, but otherwise - just keep listening to your body". Which is also why I know that my B12 improved significantly through the fast. And indeed, I did feel hunger after 21 days. (And hunger is actually a different beast than appetite - a beast I think almost no one in the western world knows - it is a feeling of "i must eat now" that does not go away when you're doing something interesting, which is very different from regular appetite in ways I can't really put into words)

Later fasts felt good, but not as good -- possibly because my starting condition was better.

2. I found a book by Bernarr McFadden http://en.wikipedia.org/wiki/Bernarr_Macfadden (can't remember the name right now) that correctly described my experience (it's hard to find descriptions at all; and everyone around has the anthonyb opinion that I'm about to die because I haven't eaten in x days). That book had very old references (from the '30s) about fasting practices in some indian castes - which I was then able to altavista (that was before Google hit the scene) and confirm

3. I consulted my doctor, and a friend who had finished his medical studies and was doing his internship at the time. Both had the immediate anthonyb reaction, but a few minutes later conceded that any of the things they feared would trigger horrible pains, blackouts, etc - and that couldn't be right as I was feeling good.

YMMV. 1) and 3) may not be available to you. 2) was available to me from the university library, but I'm not sure where I can find it today. But it was available to me at the time.

Given that you don't know that, and earlier on you didn't know what ketosis is, I'll take your dietary advice with a large grain of salt...

I did know what ketosis is. But ketosis DOES NOT induce acetone breath in 99.9% of the population*time - which is what I understood you asserted. Look it up. Really, look it up.

And you better read about b12. You are radically misinformed. Not that I care - it's your health that will suffer. Really. Look it up.

What's the top source of B12 on that list? Now, given that you're not eating beef liver, which liver do you think is providing all that B12?

Stupid. Dangerous.

Edit: Thinking about it, I'd put fasting for 3 weeks in the same class as running a marathon: if you can do it, you're probably healthy. Actually doing it though, is not healthy at all.

... Ultimately, animals must obtain vitamin B12 directly or indirectly from bacteria, and these bacteria may inhabit a section of the gut which is distal to the section where B12 is absorbed.

Under "synthesis and industrial production":

.... Neither plants nor animals are independently capable of constructing vitamin B12.[30] Only bacteria and archaea[31] have the enzymes required for its synthesis.

And a little later:

.... The total world production of vitamin B12, by four companies (the French Sanofi-Aventis and three Chinese companies) is said to have been 35 tonnes in 2008.[40] Most of this production is used as an additive to animal feed.[41][citation needed]

It doesn't matter what the top source on the list is if you can have it synthesized in your own body. Which I now do way better than I could before my first fast. You know why cow liver has B12? Because cows are fed B12 these days so that beef liver would have enough B12 for human consumption! That's so ridiculous and inefficient it is sad.

You know why B12 synthesis is so horrible among both humans and livestock today? Because of how much we use antibiotics. And there's also another surprising finding: The human body (and most other mammals as well) have a cache of the organisms required to synthesize B12 and a host of other useful stuff. It's called "The appendix", you might have heard about it. The body will release these organisms from its cache under ketosis lasting more than a few days, to replenish and revive the useful colonies. Nature is very smart like that -- a few days of fasting are completely normal when your food source dries up. So the body uses that period to do maintenance. [I'm not going to spend time looking for the refs right now, partly because I no longer have access to full article texts, and mostly because I don't have the time; But this was hypothesized decades ago, and AFAIK conclusively proved something like 5 years ago, although it's not really well known so far even among professionals who should know better]

> Stupid. Dangerous.

Religious, is all I can say about your responses. You know things to be right, like it is dangerous to fast, or (I assume, although you might already be enlightened about these subjects) that dietary cholesterol is bad for you (it's almost independent of blood cholesterol, which is an important marker, though not a cause for disease), that you shouldn't eat more than a few eggs a week (nonsense; eat as many as you want - 20 a day is not unhealthy), that low-fat dietary intake is good for you (it's not), that butter is bad for you (it's excellent for you if it's from healthy grass-fed cows), that weight change is exclusively a result of caloric balance (only in the useless tautological sense), that you should minimize salt intake (too little is as bad as or worse than too much), or that cushioning is good for your feet and that's why sports shoes have them (they're bad for you except for very specific circumstances; they were championed by marketers, not researchers).

I try to challenge my beliefs and understand why I have them. I often (way too often, unfortunately) find that things everyone (including myself) takes for granted are actually better classified as "wrong leaps of faith" or even downright superstitions than science.

When someone contradicts me (and it's something I haven't researched and do not have a good basis for my beliefs), I try to start again from a blank slate, rather than find support for what I believe in (because you always can do that, regardless of how wrong you are).

> Edit: Thinking about it, I'd put fasting for 3 weeks in the same class as running a marathon: if you can do it, you're probably healthy. Actually doing it though, is not healthy at all.

I don't think this analogy is proper.

Evolution surely did prepare you to run short distances. Evolution did not prepare you to run a marathon - you have to practice to be able to do that, regardless of how healthy you are - and I agree it is probably not healthy (although I have no support for that - for all I know, done properly, it might be super healthy).

Evolution did prepare you to survive if your food source dries up (at least for a short while), or if you sprained your ankle and can't chase your prey or climb the tree to get food. In fact, it's apparently piggybacked some maintenance jobs on this period because (at least pre- agriculture) they were guaranteed to happen relatively often.

You may argue about how long that "short period" is - evidence collected mostly from religious fasting is that it is around 40 days when you are healthy.

> if you can do it, you're probably healthy.

I disagree in general, but there's an important point here that I must stress - it would probably have been unhealthy for me, had my appendix been removed (which is not uncommon), given the explanation above. However, the reason I started fasting was not religious or weight motivated - I simply had no appetite. So I didn't eat. The appetite came back 21 days later. I have since fasted several times in periods of 7-21 days, once every couple of years, sometimes prompted by loss of appetite, and sometimes by wanting to experience the health benefits.

I would not be surprised if appendix removal would have triggered appetite much earlier. And I would also not be surprised if evolution did not prepare humans for a removed appendix, and I would have suffered some irreversible damage as a result. I really don't know about that. (If you feel vindicated about this being "stupid and dangerous" - we have a difference of philosophy here, that I'm not going to argue about)

* edit: Forgot to mention - I've been vegetarian for the most recent 90% of my life, and vegan for a nontrivial part of that - during which I never had a good source of B12. If B12 could only be sourced from food intake, I'd be dead before the age of 12 (which is why I already knew 15 years ago that the prevailing B12 theories were bullshit, despite not having a better explanation at the time). But I was only dangerously low for a 6-month period in my twenties - other than that, I was just "low, but not dangerously so" until that fast.

Just a question - would you have reacted the same if I wrote "it isn't bad for you to eat 20 eggs a day", or "eating cholesterol isn't bad for you"? because both of these "accepted wisdoms" (limit egg consumption; dietary cholesterol is bad for you) are unsubstantiated nonsense you hear from everyone (laymen, nutritions, doctors), with no study to support them. And yet they are almost never challenged.

I would have either asked you for citation, or did my own research. But even if I haven't, two wrongs don't a right make. People are biased, and selectively accept garbage. Unsubstantiated nonsense is garbage, irrespective of its acceptance by people who know nothing about it and are accepting things on what makes them feel good.

That's true, and describes 99% of what people believe. It's just that I never see any of the mainstream proved-wrong beliefs challenged on HN - they either get a response like "no, that's wrong, and here is a reference", or accepted as gospel. Not surprising, really.

No one is saying two wrongs make one right. I clearly stated that I don't have a reference anyone can check.