[anthonyb]

I'm not sure what you mean by an "instance", but there will likely be variations in how quickly people respond to metabolism, and also depends on what you're eating during the fast.

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".

[beagle3]

> I'm not sure what you mean by an "instance"

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.

[anthonyb]

Eating nothing for three weeks?! That's stupid and dangerous.

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).

[beagle3]

> Eating nothing for three weeks?! That's stupid and dangerous.

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.

[Jd]

Given what you've said here, I highly suspect you do long-term fasting within some sort of "yogic" context. I personally suspect that many of the potentially negative outcomes of dietary depravation are mitigated when in a positive environment (i.e. lots of nature / with good energies) complemented with certain types of yogic practices. There is also a long tradition of long "fasts" within Chinese qigong traditions, and the supposition is usually that a body attuned via various practices can feed off of the environmental energies (e.g. the sun, the mountain) without needing nutrients of other sorts. The technical aspect of some of these things is a bit beyond me, both because it is 'esoteric' and doesn't fit into any model of Western science that I know of (with the potential exception of Paracelsusians).

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).

[beagle3]

> Given what you've said here, I highly suspect you do long-term fasting within some sort of "yogic" context.

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.

[Jd]

Fascinating. What were the "few trustworthy references" you found? I've never heard anything like your experience before, and the anecdotal evidence I've heard regarding fasting is largely gathered from spiritual traditions (i.e. Yoga, Christian, etc.).

[anthonyb]

Your b12 will be up because your body is cannibalising its tissues to stay alive. That's your liver, kidneys, etc. and it doesn't mean that you're healthier.

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...

[beagle3]

Wow. I mean, you have all the answers!

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.

[anthonyb]

No, you go look it up: http://en.wikipedia.org/wiki/Vitamin_B12#Foods.

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.