If you look carefully at the scripture, there are instances were some people fast to pray and/or to express their sorrow. However, the length of the fast seems to be astronomical; some people like Moses has fasted for about 40 days:

Exodus 34:28: 28 Moses stayed there with the Lord forty days and forty nights, and during that time he did not eat food or drink water. And Moses wrote the words of the Agreement—the Ten Commandments—on the stone tablets.

And Jesus also fasted for about same length of time:

Matthew 4:1-2: 1 Then the Spirit led Jesus into the desert to be tempted by the devil. 2 Jesus fasted for forty days and nights. After this, he was very hungry.

Is it physically possible for us to do the same? I sincerely doubt that most people would die before 25 days.


4 Answers 4


Strictly medically speaking... Depending on your health, and the amount of stored body fat/muscle mass that you have when beginning to fast, it is physically possible to fast for more than 40 days.

Per this article: http://health.howstuffworks.com/diseases-conditions/death-dying/live-without-food-and-water1.htm

Medically speaking, most doctors agree that healthy humans can go up to eight weeks without food as long as they have water. People have gone longer and been fine, and people have starved to death in less time. Being strong and in good physical shape can help you survive longer, but so does having extra body fat. The body stores energy needed to live in the form of fat, carbohydrates and proteins. The carbs are the first thing to be used up without more food coming in. The fat goes next, which explains why people with more of it can survive longer. Then the proteins go. If you get to the point that your body is using up proteins, basically the body itself, then you're in bad shape.

Eight weeks comes out to 56 days, of course, which is above and beyone even the 40 days you mentioned.

As for going without water for this time period, medical science says no, we can't live nearly that long.

The same article says this on the next page:

Assuming you're in reasonable shape and in ideal conditions -- that is, not in the heat or cold and not exerting, a human can probably live for about 3 to 5 days without any water. Healthier humans can live another day or so longer.

However, Moses likely had divine intervention. Of course, that can't be proved outside of the Biblical account, so that would make the question unanswerable using objective criteria.

  • The Heavenly Man gives the account of a modern day example of fasting from water for longer than was possible, but supernatural intervention was present.
    – Narnian
    Sep 4, 2014 at 18:30

No. It is not possible for us to fast without food and water for fourty days in normal circumstances.

I will explain the answer as below. I base my answer on 'Celebration of Discipline' by Richard Foster.

In Bible the normal means of fasting involves abstaining from all food, solid or liquid, but not from water. In the forty day fast of Jesus (Luke 4), we are told that '

He ate nothing during those days

Luke 4:2a (NIV)

and toward the end of fast, he was hungry.

and at the end of them he was hungry. Luke 4:2b (NIV)

This indicates that he was abstaining from food, not water. I believe this is what usually involved in a fast.

We can see partial fasts as well

I ate no choice food; no meat or wine touched my lips; and I used no lotions at all until the three weeks were over. Daniel 10:3 (NIV)

Also we can see some instances of absolute fast.

“Go, gather together all the Jews who are in Susa, and fast for me. Do not eat or drink for three days, night or day. I and my attendants will fast as you do. Esther 4:16

Here we see fast as 3 days and nights without even water.

Paul also fasted this way immediately after his encounter with Christ.

For three days he was blind, and did not eat or drink anything. Acts 9:9 (NIV)

Generally it is accepted that human body cannot go without water much more than three days. That would mean both Moses and Elijah would have engaged in supernatural fast in their fast as described in Due 9:9 and 1 King 19:8

I went up on the mountain to receive the tablets of stone, the tablets of the covenant that the LORD had made with you, I stayed on the mountain forty days and forty nights; I ate no bread and drank no water. (Due 9:9)

So he got up and ate and drank. Strengthened by that food, he traveled forty days and forty nights until he reached Horeb, the mountain of God. 1 King 19:8

In both these cases we can see that a divine intervention in their life. So I believe we also should not undertake any supernatural fast, without clear command from God personally to us. So you are right, we should not undertake absolute fasts for more than 3 days unless God asks you to do so.

Now many who practiced fasting regularly starting with a meal or two and extended over time, say that fasting from food for fourty days is possible. (Source: Celebration of Discipline)

  • 1
    Surprising fact: Someone I know did fast drinking only water for about 10 days. Sep 24, 2011 at 19:09
  • 1
    @Sonic: That's not surprising; a healthy human being can last about 56 days with only water.
    – user32
    Sep 25, 2011 at 22:31
  • 1
    @Soft The person in question was very thin. Sep 26, 2011 at 0:57

I just wanted to add the story of this woman: Water Only Fasting - 1st of 3 Forty Day Fasts, which shows that such fasts are possible. (She did however take certain vitamin supplements, but none that contained any calories). As for dry fasting (no water, no food), there are also reports of this being possible: Fasting Dry: A Biblical Path.


I myself, personally, have fasted without food for 40 days and 40 nights. I have done it twice. Both times were last year (for a total of 80 days). I took no vitamin supplements. I drank water. By the end, I found that I needed to drink bottled water, because the chlorine in the city tap water became overwhelming.

I did not "work up to it". The 40 day fast was the first fast I ever did. Then I fasted for 10 days. And then I did it for 40 days, again, a few months later.

I went to work and did all of my normal things, and hardly told anybody. They noticed I was getting thinner. That is all.

  • @TheFreemason - I've deleted the comment because while it may be a valid suggestion, it's not one of the valid reasons for commenting. Debating the wisdom or foolishness of something like this isn't what the question asked, it just asked if it's possible. We need to try to keep the comments from being a place of discussion. Sep 5, 2014 at 1:46

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