How much time can we spend without eating?

Living things fulfill three vital functions: nutrition, intercourse, and reproduction. Human beings, as such, nourish, connect and reproduce. And it is in this nutritional function that our survival lies, to a large extent. Without food, we can not survive.

In fact, despite the fact that we have created an artificial environment where we never see our lives in danger due to lack of food, in nature everything is based on a struggle to eat and avoid eating With Through nutrition, we get no not only the energy needed to keep our physiological functions constant, but also the matter needed to regenerate our body.

And the body, when it needs us to give it matter and energy, warns us of this with the unpleasant physical and psychological sensations of hunger. But what would happen if we completely eliminated food? How much time can we spend without eating? What is the maximum time we can survive without food?

Get ready, because in today’s article we will take a trip to the limits of the human body to discover not only why the body “turns off” when we deprive it of food, but also how much time we can go without eating before we die With Prepared? Let’s get there.

How much should we eat per day?

Nutrition is the metabolic process through which energy and matter are transformed through cellular reactions that manage to keep the body alive with stable physiological functions. Functions are the vital function that all living beings perform to have the matter needed to make up tissues and the energy needed as fuel for our biological functions.

Humans carry heterotrophic food In other words, we use organic matter itself as a source of matter and energy, delivering inorganic substances as a waste product. In particular, we are holozoic organisms, which are those heterotrophs that receive organic matter from the ingestion of other living beings.

We eat solid or liquid foods that come from the anatomical parts of other living things (animals, plants, fungi …) that will be degraded by our digestive system in order to break down complex molecules into simpler ones. thus obtaining various nutrients: carbohydrates, fats, proteins, vitamins and mineral salts.

These nutrients, after being absorbed and assimilated, undergo various metabolic degradation processes in which various enzymes convert nutrients into molecules that can enter cells and thus undergo cellular processes that transform molecules from food into ATP .

ATP (adenosine triphosphate) is a molecule whose bonds, when broken, release energy. In this sense, the body’s cells use this ATP obtained from the metabolic processing of nutrients as an “energy coin”. When they have to perform a biological function, they break down the molecule and the energy released is used as fuel.

And famous calories are a measure of the energy produced by our cells after food degradation and ATP intake. That is, we eat that, in addition to having a source of carbon and matter to regenerate the body, to get these ATP molecules and, therefore, this energy in the form of calories that will be used to keep the body stable .

And it is no longer that every nutrient provides a specific energy, but that every food, depending on its proportion of nutrients, water content and production process, provides certain calories. This is why it is so difficult to determine how much to eat each day.

Be that as it may, and regardless of whether daily calorie intake depends on the caloric expenditure we make (a sedentary person is not the same as an athlete), the WHO (World Health Organization) determines that women need 1,600 to 2,000 calories a day to meet their requirements; while men need 2,000 to 2,500 With All of these are approximations, but the really important thing was to understand why we should eat. And the answer is clear: it gives us the material for our body and energy in the form of ATP that we need to stay alive.


What happens when you starve to death from the food body?

Now that we understand what human food is based on, we need to look at what happens to our body when we stop eating. We will put the human body on the border. Let’s see what reactions occur in the body when we completely deprive it of food.

Carbohydrates are the main form of fuel for our body. Of all the macronutrients, they are the ones with the highest energy efficiency. Therefore, just 6 hours after stopping eating, the body will continue to use these carbohydrates , converting these nutrients into glycogen, an energy reserve polysaccharide.

Glycogen is the main storehouse of energy. So during the first hours of food deprivation, there will be no change at the systemic level. Now, as glycogen stores are depleted, the body, which will want more carbohydrates, will warn us of hunger.

What if we still do not eat? Well, the body, despite warning us that glycogen stores are running low, will continue to rush to the end. Now, when there is no easily accessible carbohydrate store, which, although it depends on how much we ate last time and our metabolism, usually occurs about 72 hours (3 days) after the last intake, the body will turn to fats .

Therefore, after about three days without eating, autophagy begins. The body is “eating” itself. Initially, it will feed on adipose tissue, which has a very low energy efficiency, although the emergency situation requires it. We are forcing the body to consume fat deposits. And this is when significant weight loss begins to appear.

This situation is known as ketosis, since the emergency breakdown of fats culminates in the generation of ketone bodies or ketones. With These molecules will serve as energy fuels (we no longer have glycogen left), but let’s not forget that the body is eating itself and uses a metabolic pathway that uses only when absolutely necessary.

When we get into ketosis, different things happen in our body:

  • Ketoacidosis : Ketones are acidic and change the pH of the blood, which affects the transport of oxygen and, if the situation persists, can be life threatening. It is a serious circumstance and, the more time without eating, the greater the breakdown of fats, the greater the amount of ketone bodies, the higher the acidity of the blood and the less the transport of oxygen.
  • General Concern : Lack of energy on its own, the body seeking food and the physical and neurological changes caused by ketones will cause symptoms such as headaches, insomnia, hallucinations, bad breath (from ketone bodies), fatigue and extreme weakness, concentration problems, mood swings, decreased cognitive abilities, skin rash …
  • Loss of muscle mass : The body is literally eating itself. When ketosis begins, there is a significant gradual weight loss, with a clear lack of strength, extreme weakness, problems with walking …

But what happens when fat reserves are depleted? Well, the countdown begins. The body, even more desperate, will try to get energy from the degradation of proteins (the body will eat its own muscles), an even less efficient metabolic reaction. At that time, the lack of energy will be great, a very strong stench will be detected, characteristic of this degradation of the body’s protein reserves, loss of bone density, severe immunosuppression, weakening of vital organs for due to lack of energy and muscle loss … If the situation is not reversed, death is near.

So how long can we survive without food?

You may be surprised that we have not given clear dates as to when each of the fasting reactions we have discussed occurs. But we can not. And is that it all depends on the level of hydration of the person, his state of health, their metabolic rate (we know that the thyroid plays a very important role in the progression of stages) and, above all, fat reserves the person has when it starts ketosis.

In fact, it is estimated that an adult weighing about 70 kg can live without food for 1 to 3 months. As we can see, the range is very wide. Even so, most people who went on a voluntary hunger strike and did not stop died after 45-60 days without eating anything . Therefore, the most realistic thing to say is that we can survive for about a month and a half without food.

In this sense, a healthy individual who gets enough hydration (very important) can endure without much trouble or consequence for about 30 days. Beyond that, the risk not only of long-term problems, but also of death, increases greatly.

In any case, what is clear is that the survival time in total fasting depends on many different factors (body fat level, metabolic rate, age, hydration, previous physical condition …), although it is believed that it is practically impossible to survive more than 70 days without eating anything With the human body generally spends 40 to 60 days without food.

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