The Science of Starvation: How long can humans survive without food or water?

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Rita Chretien, a Canadian woman survived being stranded inside a vehicle in Nevada for 48 days, by eating only some trail mix and candy, and drinking water from a stream.  Apparently, she and her husband were following their GPS instructions on their way to Las Vegas from British Columbia when they took a rural road that essentially turns to a bog in the winter months. Their van eventually got stuck in the mud in the middle of nowhere, and they both waited for help for 3 days without sighting anyone. At this point, Albert Chretien, the husband, left to seek out help, while Rita remained inside the van. When she was found by a group of hunters just last week, she was nearly dead and had lost some 30lbs. Her husband remains to be found.

This recent story of near complete starvation highlights the human ability to survive for long periods of time without sustenance.

Due to obvious ethical concerns, there is not a whole lot of credible scientific data on the topic of starvation and survival. Instead, there are many accounts of either voluntary or involuntary cases of complete or near-complete starvation that allow us to make some very general conclusions.

One of the most well known cases of voluntary starvation, is the hunger strike of Mahatma Ganhdi. During his protest, Gandhi ate absolutely no food and only took sips of water for 21 days, and survived. What extraordinary about this case is the fact that Gandhi was very lean when he started his hunger-strike, thus not having much energy reserve from the outset. Also, it must be noted that during his life, Gandhi is reported to have performed a total of 14 hunger strikes.

In a 1997 editorial in the British Medical Journal, Peel briefly reviewed the available literature regarding human starvation. Generally, it appears as though humans can survive without any food for 30-40 days, as long as they are properly hydrated. Severe symptoms of starvation begin around 35-40 days, and as highlighted by the hunger strikers of the Maze Prison in Belfast in the 1980s, death can occur at around  45­ to 61 days.

The most common cause of death in these extreme cases of starvation is myocardial infarction or organ failure, and is suggested to occur most often when a person’s body mass index (BMI) reaches approximately 12.5 kg/m2.

Of course, one would expect marked variability between 2 individuals in their ability to endure starvation. As suggested in a Scientific American article by Alan Lieberson,

The duration of survival without food is greatly influenced by factors such as body weight, genetic variation, other health considerations and, most importantly, the presence or absence of dehydration.

I would add that body composition would also likely play a key role; for the same body weight, the individual with a greater percentage of body fat has a greater on-board storage of calories. Also, a lower muscle mass would generally be associated with reduced caloric consumption. This by extension would suggest that females may have a survival advantage over males due to their greater relative fat stores.

Most important factor of all, however, appears to be hydration.

In the example that started this post, Rita Chretien survived her 48 day ordeal in large part due to the availability to some melted snow for drinking. Indeed, had no water been available, Rita may not have fared as well. In examples of hospitalized individuals who are in a persistent vegetative state, who become cut off from artificial sustenance, death ensues within 10-14 days. Keep in mind that these individuals are in a coma and completely immobile, thereby consuming the lowest amount of energy possible. It can thus be surmised that the same conditions (no food or water) in a person who is at least somewhat active, and who may perspire, would only lead to a much swifter end.

For individuals who like to get out into the wilderness, and who upon reading accounts of other’s misadventures (Into the Wild, 127 Hours, etc.) are not in the least discouraged from following suit (present company included), ensuring to always have a reasonable supply of water should be priority number one. Additionally, as is well documented in the eventual demise of Christopher McCandless (Into the Wild) the avoidance of eating unknown plants and shrubs can also be a key survival strategy.


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Peel M (1997). Hunger strikes. BMJ (Clinical research ed.), 315 (7112), 829-30 PMID: 9353494

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20 Responses to The Science of Starvation: How long can humans survive without food or water?

  1. The story about the woman trapped in the car is almost enough to make you start carrying around a bag full of MRE’s. Yikes.

    The Nerd Connection

  2. biobabbler says:

    A few things.
    1) super interesting, thanks.
    2) I read ages ago in undergrad that when in starvation mode (once you are in ketosis) your requirements for water each day go WAY down (I think as low as 1/2 cu/day). Clearly this is adaptive (or lucky?) if in tough times. Regardless, have you heard something like this and if so, do you have a citation for it? I remembered it but could never find a citation (my advisor asked for it, oh, 15 years ago? =) ).
    3) THANK YOU for that last part re: yes, go out, explore the world. It’s a wonderful world and you deserve to see it! Just prepare, read books, practice, train, etc. And ask experienced folks questions and start small, and with more experienced people, if possible. It’s GREAT fun and the natural world is profoundly beautiful and restorative.
    4) PEOPLE NEED TO USE REGULAR MAPS. Good paper maps very clearly mark which roads are BIG and THROUGH and which are obscure numbered/nameless forest service roads that I’ve had googlemaps tell me to take to get (literally “turn left at nameless road”), for example, from Mount Rainier National Park to Seattle. Ridiculous 4wd-summer-only route vs. regular highways. BRING GOOD PAPER MAPS. Former NPS, so I know SO many people would benefit from this simple step. Plus, what if the GPS/batteries die? Paper map still works.

    Super interesting. Thanks so much. =)

    ps in biochemistry our teacher ran some calculations re: how long you could go without eating (if drink water and take vitamins) if you were 50, 100, 150, 200 lbs overweight, etc. STUNNING. I remember one weight category meant you could not eat for a YEAR. WOAH!

  3. You might be interested in reading: “The Great Starvation Experiment: Ancel Keys and the Men Who Starved for Science”, which is a historical narrative about Keys seminal starvation study. It’s an incredible read.

    Here’s the link if you are interested:

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  8. dick says:

    great news! because im poor and havent eaten in awhile….this is fantastic news! i can go 20+ days without food…oh fuck my life.

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  10. jamie says:

    i am trying to do a hunger strike. its been 5 days and I’m starting to feel really sick. I weigh 120 pounds (well, i did when i started). I am shaking and unable to stand up. This article made me feel like I could do more but Ghandi must have worked up to his 45 days. I am disappointed in myself now because its going to be hard to nurse myself back to health. Caution, non-ghandis.

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  12. christine says:

    my dad is in hospital …and has had nothing to eat for over 35 days now …they are keeping hydrated ………..cant understand why they are doin that ….he has lost 5 stone in body weight…i realy dont no how he is still here 2 day

  13. Tammi says:

    Eat for crying out loud.
    My twin sister is dying of stage 4 cancer, too young to die. She has no choices, the decision has been made for her. It has been weeks with no food but she is still drinking because she does not want to die.
    If she had a choice, she would eat.

  14. Katherine says:

    It’s a wonder I’m still alive….due to being homeless and not having money I’m surviving on coffee and water and, if I’m able to find enough change on the ground of if one of my friends finds out, then and ONLY then am I able to eat. Today is day 7 and I’m sick to my stomach, my vision is extremely blurry, and every time I try to stand up I feel as though I’m going to fall down. My situation is not my fault, but I think it’s God’s will that I’m not dead yet (by the way I’ve been going through this since July….8 months now).

  15. Jim says:

    i need answers for a dumb class and my teacher is ………..

  16. Dante says:

    I can’t see how starvation can cause myocardial infarction (which is caused by an occlusion of the coronary arteries). But hypoglycaemia can definitely cause cardiac arrest and is one of the reversible causes.

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  18. cmaglaughlin says:

    Activist Dick Gregory once went 70 days without eating, just drinking a gallon of water a day. He was under the supervision of a doctor’s care. What’s so shocking is he walked and jogged 100 miles straight the very day he ended his fast! Sun gazers claim they can go TOTALLY without eating, sucking up the energy of the sun.

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