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I've been trying to find the US Military's guidelines or standard for how long a soldier can go without food, for any branch of the military.

Is there any such recommendation, as to how long a man can go without food (and what activity level he can be expected to perform to)?

  • do you want reference from an old field handbook? i mean, quite old and not current. then there's the question on whether such information would be classified for restricted release. i'm sure that many a military or other such body has watched prisoners starve, and so that information is certainly available in a few places if you don't care too much for the source — but you probably already thought of that – can-ned_food Dec 13 '17 at 1:29
  • Are you interested specifically, only in food, or water too? I just thought about that after I answered, and depending on your response I might delete my answer if I can't find more info to provide in it. – Aaron Dec 13 '17 at 17:26
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    Deleted my answer since JohnP's is much better, but I want to convert the emphasis of it to a comment here: There have been deaths of soldiers due to dehydration even when water is available, due to their leaders withholding an amount of water that they believe will not cause death. Therefore, if they are working off of a military-provided "drink this much to stay alive," then take that information with a grain of salt and do not put it to the test if you want to stay alive. That is for water, but I would advise similar for food. – Aaron Dec 13 '17 at 20:18
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    "How long can they go" is broad in that there can be different ways of measuring this. How long can they go: before dying?, and stay alive?, before losing a reasonable amount of operational capability?, before becoming unhealthy? To make the point even clearer: if you completely starve yourself, there comes a point late in the process at which you are still technically alive but which you cannot recover from and will die even if you start to eat again: technically alive but as a "dead man walking." You probably want "remain somewhat operationally capable and not die" or similar. – Aaron Dec 13 '17 at 20:25
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    On further thought, the military is unlikely to have information about what happens with a complete lack of food because they are unlikely to encounter that scenario. I am not sure if all military members receive some survival training or if it is only a (likely large) subset, but I am assuming all receive some training. This means a soldier eating absolutely nothing is either incapacitated or lazy/ignorant since there is at least some food almost everywhere on the planet. That is probably why the studies are about low-food (bugs/leaves/roots) rather than no-food, as JohnP's answer suggests. – Aaron Dec 13 '17 at 20:30
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TL; DR - I don't think there are any actual existing guidelines for how long a soldier can go without food. There are recommended minimums for various operational capacities. As has been pointed out already, water is of much more importance, and there are numerous performance studies showing athletic impairment at levels as low as 5% dehydration.

Long answer:

I cannot find (And having been in the medical side of the military for 10 years I do not remember any minimum guidelines on food deprivation) anything current mandating that soldiers cannot go more than X days without food.

However, the minimum caloric needs of soldiers and various Special Forces (SF) units around the world has been studied quite a bit, as well as what happens with physical and cognitive performance in periods of both sleep and food deprivation. You could compare that with the extreme limits of food deprivation before death and come to an answer.

I apologize in advance, some of these I do not have access to the full study.

This study looked at both food and sleep deprivation (Admittedly for a civilian group going through survival training), and concluded that within 24 hours, subjects showed marked decline in several cognitive areas. Food deprivation was less dramatic than was sleep deprivation. (And this has been proven in real world studies, many people start hallucinating with sleep deprivation long before food deprivation would have an effect).

This is one of the better studies I found, as it compared energy requirements over different SF groups in different regions, as well as under different stresses. The section for the US Rangers showed a daily calorie deficit of 1200 calories (The data is given in MJ, which is ~ 240 kilocalories) per day. They showed a surprising amount of weight loss (16% vs an expected 10%), but not as much strength loss as they expected. This was not, however, complete deprivation but merely shortage, and presumably balanced nutrition for what they did get.

A very interesting paragraph:

Soldiers provided an additional 1.7 MJ/day supplement during the 8-week Ranger course converted approximately half of the additional food energy to body energy stores, and used the remainder to fuel higher energy expenditure [8]. This presumably reflects a lifting of the ceiling on TEE that is imposed by inadequate intakes, as in studies of undernourished Columbian school children playing soccer alongside adequately nourished children [27], when energy intake appeared to limit work performance. Earlier studies of laborers, such as sugar cane cutters and road builders, also support the idea that inadequate energy intake constrains energy expenditure 2.

This suggests that when in a period of caloric deficit, the body limits the amount you can do before exhaustion, and when calories are restored, the activity level also rebounds.

I admit, I did not read the entire chapter, but most of the methods for establishing MDRI (Military Dietary Reference Intakes, or RDA for soldiers) can be found here, albeit slightly dated (2006).

This PDF from 2001 does give a minimum of 1500 kilocalories for restricted rations, which suggests that at a minimum, soldiers must get that amount on a daily basis to be able to function at any operable level. You might be able to extrapolate from that how long without food before a soldier becomes unable to function (Again, paying attention to the water factor).

If you are interested in pursuing the research rabbit hole, there are numerous linked studies cited as reference in the studies I linked, and google scholar will have many available for perusal. I realize this doesn't quite answer the full question, but it's like trying to prove a negative, I'm not sure they even exist in the form you are seeking.

  • You have found much better information than I was able to provide. Deleted my answer and +1 yours. – Aaron Dec 13 '17 at 20:14
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I see that nobody has weighed in on this, I think because there is an old saying that "an army marches on its stomach" (N. Bonaparte). The armies of the world would probably focus more on how to get nutrition, rather than how long it is ok to be without. Due to physiological differences (I'm not a doctor BTW) between individuals, there is sure to be a wide range of tolerance for starvation before different humans are unable to function to whatever degree is your benchmark.

I have some experience through my brother who coaches wrestlers. These young men routinely starve themselves to make lower weight classes, all while working incredibly hard and expending extraordinary amounts of energy. When I expressed my concern about long-term health effects, my brother said something that made some sense to me: "Humans are genetically built to be able to keep working through periods of fasting, how long depends on their mental and physical fortitude".

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    The wrestler's logic nonetheless fails to acknowledge the real verified dangers of that practice. – whatsisname Dec 9 '17 at 5:52
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    "Humans are genetically built to be able to keep working through periods of fasting", may be true, but its not the whole truth - we are also genetically build to perform better when not fasting. – user5330 Dec 10 '17 at 1:52
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    Thank you for the answer. I do hope someone can find a military guideline for it, but I think you did well in answering. – Johnny Dec 10 '17 at 8:46
  • There is scientific literature on cycles of scarcity and plenty among early hunter-gatherers, and whether the genetic adaptions to deal with this seesaw are one of the causes of diabetes in modern people. There is also a vast literature on fasting. I remember a description of the gorging when an elephant was killed, and an comment that gorging is a reaction to periods of scarcity. I don't feel competent to synthesize this literature, but will only comment that we probably have (had ?) some genetic adaption to starvation/gorging, or homo would have starved to death a million years ago. – ab2 Dec 10 '17 at 15:32

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