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According to Deuteronomy 9:9, Moses did not eat or drink anything for 40 days.

When I was gone up into the mount to receive the tables of stone, even the tables of the covenant which the LORD made with you, then I abode in the mount forty days and forty nights, I neither did eat bread nor drink water.

Is this possible from the scientific point of view? My guess is that no water for that long time must be impossible. How about no meals?

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The better-known Bible passage featuring a 40-day fast is the one where Jesus fasts, in Matthew 4:2. –  dancek Aug 22 '11 at 12:04
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According to some old (although not biblically old) interpretations of Jewish law, it was considered fine to chew a food as long as one spit everything out before swallowing, including one's saliva. I am not sure, but it might be possible that one could get some amount of nutrition/hydration from chewing food. –  ESultanik Aug 22 '11 at 12:19
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The NKJ translation to "neither did eat bread nor drink water" does not necessarily mean "did not eat or drink anything" (but...I don't know Hebrew so I can't tell you if "water" literally means "water" or "water, wine, goat's milk, and all other liquids."). Also, I know someone who did the no meals thing for 40 days; he looked terrible at the end. –  David Murdoch Aug 22 '11 at 15:20
    
@DavidMurdoch: the hebrew text literally says "I did not eat bread, and I did not eat water". It is supposed to be understood as meaning all types of food and drink. But the words for water and bread have only their usual meaning (i.e. water is just water, not other liquids). –  Tomer Vromen Jan 26 '12 at 21:17
    
I misread "Fisting for 40 days - is it possible?", hehe :) –  Camilo Martin Apr 16 '12 at 11:51
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3 Answers

"Comment in passing"—the biblical term "40 days and 40 nights" or similar can be used to mean "a long time". Whether this is the case in any given passage would need to be understood, but is outside the scope of this question.

In any normal circumstance you'd be dead long before 40 days without water.

But hunger strikers regularly live beyond 40 days and purposeful fasting for that period is not unknown.

As an example of what this may do to the body, assume that a person fasting is largely immobile and can survive on a 500 kcal daily energy budget. Available calories from food are about 4 kcal/gram for carbohydrate, 5 kcal/g for protein and 9 kcal/g for fat. Start by assuming that body resources can return say 6 kcal/gram if "living off your own body.

  • 500 kcal per day requires 500/6 ≈ 85 grams of body mass.
  • 40 days requires 40 x 85 ≈ 3400 grams ≈ 3.4 kg of body mass.
  • Even doubling that to 1000 kcal/d requires about 7 kg of body mass.

Obviously there are many other factors to consider, and the above mass loss seems 'rather low' compared to expectations, but is an indication that energy availability is not the major factor involved.

This document—Adult Malnutrition in Emergencies—advises that hunger strikers experience "severe metabolic disturbance after 3 to 4 weeks" (ie 21 to 28 days) and death in 6 to 10 weeks (42 to 70 days). ir 40 days would be "pushing your luck".

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Nice answer. Can you add a reference to where you found the cal/g figures? if the source is the document, could you mention that it is the case in the answer? –  Sklivvz Aug 22 '11 at 12:13
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+1 can you also explain why 40 days without water is a certain death? –  Fitri Aug 22 '11 at 14:12
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@Sklivvz: I know, but this is a skeptics site :P Also, the answer apparently assumes body nutrition is converted 100% to energy. Is such efficiency normal? –  Fitri Aug 22 '11 at 14:27
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@James, it doesn't matter what base the number system is; if the average person has the equivalent of a second-grade education, there's a limit to how high people can count. –  zzzzBov Aug 22 '11 at 20:32
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@zzzzBov Then why would they choose 40 rather than a maximum of one digit in the number system? –  James Aug 22 '11 at 20:36
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Wikipedia has different articles in English and German about hunger strikes. The English version talks about people dying after 52 to 74 days of strike and it looks as if it is the lower bound. One Person, Swami Nigamanand, is reported to have died after being on a hunger strike for 115 days. There are several other numbers in between, and not every incident ended in the death of the hunger strike performer.

The German Wikipedia talks about 50 to 70 days strikes, which can be survived, but this sounds like an upper bound. The article is much shorter and concentrates on well known cases in Germany.

But there is a link to the medical aspects of hunger strike and a english version too. To summarize them: In the beginning, a typical weight loss is about 1kg/day, later 0.5kg/day.

Normally, a person will die without water after 3-4 days, but depending on weather circumstances, this can be shorter (1d, hot, dry) or longer (10d, cold, wet). Without food, but with water, healthy persons should survive 30 to 200 days. A critical question is, whether you get minerals and vitamins, or not even that.

One kg of body fat can be used like 30 MJoule or 7.000 kcal energie.

Afaik, we don't know much about the kind of diet which Moses or Jesus would have performed, and in which physical condition they started. Did they drink, and if they did, just water, milk or juice? If I remember correctly, the Bible claims that John Baptist ate locusts, which have a lot of proteins; did Jesus too?

My conclusion from this information is, that - apart from being just a written story - a 40 day fastening is hard, but possible - not a miracle, but a stunt of discipline. But 40 days without water is impossible; that's a lie.

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The main problem with the passage is hydration -"nor drink water". I think it is hyperbole or translation error from the original Hebrew text. –  Daniel Iankov Aug 23 '11 at 21:20
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I don't think it is translation error. Hundreds of theologians have nothing to do than argue about translation and interpretation of the text. I put more emphasize to the 'no! impossible' in the last sentence. –  user unknown Aug 24 '11 at 20:33
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You might want to check Will we be able fast like the fasts described in Bible ? on †.SE as this is a good answer and would answer the other question, too! –  dancek Sep 24 '11 at 19:20
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No, thank you, but you already linked this entry. I don't like to repeat myself, and I don't like to argue whether the bible is therefore talking about a miracle, is lying, talking about an illusion, is bad translated or a metaphor for something else. :) No, thanks. –  user unknown Sep 25 '11 at 21:41
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There was a single study published in 1973 in which an obese man, under close medical supervision, fasted for over a year. He took water and some vitamin or mineral supplements but no food.

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