Food is important. You can find people sitting down with friends to enjoy a delicious meal all over the globe. We bond, build relationships, and enjoy company while satisfying our taste buds. Nevertheless, food is more important than that. You need food to survive.
Well, that make sense- food is a biological necessity. But what happens if we take food off your table for a day? Three days? A month? Your life would unravel quickly- and we’ve been asked a few times to address just how quick that would be. The answer to this question let us be more prepared allow us to improve our survivability. So, this week we’ll dive in for the answers to a great question: how long can you survive without food?
- Survival Rule of Three
- Medical Opinions
- Trial and Error
- How Your Body Reacts
- Surroundings and Environment
- Fasting vs. Starving
- How Long Can You Survive Without Food?
Survival Rule of Three
The Survival Rule of Three is a well-known rule of thumb that describes the basic survival rules using the number three. The rule states that you can survive:
- 3 minutes without air
- 3 hours without shelter
- 3 days without water
- 3 weeks without food
We go into much more detail in our breakdown of the Survival Rule of 3.
The threes make the rule easy to remember, but as you may have guessed- it isn’t exact:
- A German diver has held his breath for 22 minutes and 22 seconds
- Shelter requirements depend on weather and the environment
- An Austrian man survived for 18 days without water
- A hunger strike participant lasted 74 days without food, verified by a doctor
These anecdotes blow up the idea that the survival rule of three is consistent for everyone in any situation. To get a better understanding, we’ll need to turn to another source: the medical community.
Dr. Alan Lieberson has quite a lot to say on the subject of starvation and fasting. He states that total sustenance (food combined with hydration) is much easier to study, and that they have much more effective data.
The grim example provided talks of people in a persistent vegetative state (PVS), and how long they last after the feeding tube is turned off. Almost all patients die between 10 and 14 days. This, however, is an example of how severe dehydration is the survival-limiting factor and not necessarily the lack of food.
Besides incapacitated patients with feeding tubes, doctors also encounter starvation in patients with anorexia nervosa, malignant tumors, or participating in ‘starvation diets’. In these patients, doctors see organ failure and myocardial infarctions commonly. Even still, patients admitted and exhibiting starvation symptoms typically do not last beyond 14 days from their last meal.
Trial and Error
The University of Minnesota gave us a better look at how food impacts our survivability with an experiment conducted in 1945. It was named the Minnesota Starvation Experiment, and they surprisingly had over 200 volunteers. They selected 36 males to participate in the trials and they were tasked with losing 25% of their body weight. Most of these men were selected from the Civilian Public Service (CPS)- an alternative to military combat service for conscientious objectors.
It sounds crazy, but the University of Minnesota was not just putting on a spectacle- they were conducting this research to assist in the war effort. The test helped researchers and scientists understand what the body goes through during starvation.
The results were published in a two book set “The Biology of Human Starvation”, which is still considered a landmark reference on human starvation. The research leaders, Dr. Keys and Dr. Brozek would go on to become a recognized psychology historian and a proponent of the Mediterranean diet and popularizing the body mass index (BMI).
How Your Body Reacts
There is an enormous amount going on physiologically and psychologically when your body is depraved of food. A few of the important transformations include:
- At the six-hour mark, your body may run low on glucose. A process called Ketosis will start to crop up in order to find much-needed energy. Your body will start to break down fat to use as energy, leaving behind acid buildup. This will lead to impaired cognitive function.
- At the three-day mark, your brain gives the command to break down protein stored in your body to find further glucose reserves. This break down releases more acid: in the form of amino acids. The amino acid can be converted into glucose.
- Now that the brain is receiving elevated levels of glucose from amino acids, cognitive function is restored but your muscle mass begins to steadily deteriorate.
- During this period, menstrual cycles will likely stop for women and your bone density will begin to weaken.
- After one week of not eating, your body’s immune system will no longer be supported leaving you at high risk to bacteria and viruses.
- At two weeks, your respiratory quotient (RQ) will show that your body has adapted to starvation with minimal protein oxidation with a 0.6 reading. This indicates that fat oxidation has been your main source of glucose production. You are almost fully converted to running on tissue reserves and food intake would need to be gradually reintroduced to reverse this.
- Each day brings you successively closer to death, with no nutrients coming in and your body self-cannibalizing to produce glucose energy until complete organ failure, starting with the kidneys.
Dr. Lieberson, from earlier, states that “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.”
Surroundings and Environment
Your surroundings and environment can impact how long you can survive without food just as much as your own physiology.
Energy is what your body needs to survive, and any environment that requires you to work harder or use more energy to survive will shorten your survivability. In many disaster and emergency situations, your caloric intake has to increase to match your increased activity. This makes it much easier to start starving.
One of the harshest environments you could find yourself in is the desert. A desert is a barren area of land: without water and vegetation. You can still find food in a desert, but it is much harder than any other area on earth. 33% of the world is covered in desert, and if you find yourself without food in a desert your survival timeline can be drastically shorter.
Fasting vs. Starving
Sometimes confused for each other, fasting and starving are not the same.
Fasting is not eating or drinking (except water) for a set period of time.
Starving is when you severely miss nutrients required to survive. If you fail to eat adequate amounts of protein, carbs, fats, and vitamins and minerals- you are also considered to be starving.
Both fasting and starvation can be voluntary or involuntary. Protestors often resort to fasting as a non-violent protest tactic. You may be required to fast before a medical procedure. Starvation happens in more severe cases, and if fasting gets out of hand it can become starvation.
The main difference between fasting and starvation is the severity of the symptoms. Fasting may leave you with hunger, dizziness, lightheadedness, headaches, and general fatigue. However, starvation will lead you to brain dysfunction, convulsions, and heart failure- just to name a few.
Fasting has been a popular diet technique for some time, and are sometimes called ‘starvation diets’. This accounts for many of the cases that medical practitioners encounter for starvation. These diets can be dangerous, and can lead to acute myocardial infarctions for those that take them too far.
Many types of animals are known to fast. Bears, penguins, and seals fast without both food and water for several months at a time. It is important to know that they do not starve in these periods. They have biochemical adaptations in how they metabolize protein that allow them to survive.
Everyone’s body chemistry is different, but the steps that follow your last meal as you approach and enter starvation are similar for everyone.
How Long Can You Survive Without Food?
After reviewing survival rules of thumb, medical observations, statistical observations, and how other factors can affect survivability, experts agree that fourteen days is the best approximation for how long you can survive without food.
You can caveat this with the fact that there is a high degree of variance, and an emphasis on how dehydration speeds up starvation drastically. It never hurts to stay hydrated, and most demonstrated starvation cases that go well beyond two-week mark were people that were very well hydrated.
References and Sources
Castellini, M.A., Rea, L.D. (1992). The Biochemistry of Natural Fasting at its Limits. Experientia. 48, p575–582 (1992). Retrieved from: https://doi.org/10.1007/BF01920242
Lieberson, A. (2004). How Long Can a Person Survive without Food? Scientific American. Retrieved from: https://www.scientificamerican.com/article/how-long-can-a-person-survive-without-food/
Baker, D., Keramides, N. (2013). The Psychology of Hunger. American Psychological Association. 44, 9, p56. Retrieved from: https://www.apa.org/monitor/2013/10/hunger
The Final Word
Food is important. We don’t eat it just because it tastes good- it is required for our survival. It may be the last bullet point in the survival rule of threes, but it is still one of the most important elements of survival. Without food, you will quickly lose energy for other survival activities, and slowly waste away as your body consumes itself.
This is why food storage is a priority for prepping and survival. Everyone should have a food stockpile to last through a small regional disaster or emergency. The target for this is typically a three-months of food storage. You can use a mix of canned goods and pre-packed food storage kits to get there easily and relatively cheap.
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