How long can you live without food?

We have moved onto the least important of the PLWF survival priorities, Food. This priority is not even a factor for short term survival; so how long can you live without food? Generally speaking the human body is able to survive for around 3-4 weeks without serious implications and to around 4-6 weeks before death. That being said you will struggle after 3 or 4 days to function at the higher levels you will be used to and will move a lot slower than normal… But might not even notice ?

What exactly is food?

Food is made up of 3 main macronutrients – Fat, Protein and Carbohydrate. Added into this are other nutrients essential for health that include water, vitamins and minerals. All of these nutrients are found in plants and animals, sorry vegetarians, humans need meat AND plants to thrive. All of these are essential to continued survival; albeit not needed to be consumed every day as the body can store some but they will have a bearing on how long you can survive without food.

So what did the Flintstones do?

The human body has managed to evolve itself over millions of years into a survival machine. It has several mechanisms to ensure that regardless what food is, or more importantly isn’t available, it will still function.

If we look back 20,000 years and focus on how humans used to eat we would see a stark difference to today. They would not have the local supermarket that they could visit on a regular basis (Spoiler alert – The Flintstones was not historically accurate). They didn’t have farming, refrigeration or comfort foods like ice-cream or Frappuccino’s. It was a harsh way of life that meant early humans were only 1 meal away from being in survival mode.

Good old Fred and Barney had to get out into the wild and hunt for food whilst at the same time not get eaten by sabre tooth tigers and bears! Wilma and Betty would be found foraging for nuts, fruits and other plants with Bam Bam and Pebbles in tow close to their cave.

Vitamins and minerals

Vitamins and minerals

Let’s start with vitamins minerals and water. We have already discussed water and why it is essential for every cellular function so I will leave that there. Vitamins and minerals are the parts of food that are used to provide things like bones, help blood to fight infections, your brain to function, your nerves to fire etc. every bodily function requires some sort of vitamin or mineral for it to work in some capacity. In short, they are absolutely essential to life and will ultimately decide how long you can live without food as infection is normally the killer.


So now the evil carbohydrate and why it’s important. Your brain weighs around 2% of your total body weight but consumes 20% of the body’s total energy. Your brain CANNOT function without some form of energy, to keep things simple; this comes in the form of glucose. It can use something called ketones but that’s for another day.

Your body can get energy from carbohydrate quickly and efficiently and will always use carbohydrate as its primary source of energy when it’s available. To do this it breaks carbohydrate down so that the glucose part is usable by the body. Carbohydrate only really comes from plant matter in any useable quantity and not meat.



Fat is sourced primarily from meat and in smaller quantities from plants, mainly in the form of seeds. Modern diets, and bizarrely government guidelines, shun fat as being the greatest evil known to man. That is just silly and against what actually happens in nature and how the human body is designed to function (and has done so for 2.5m years).

Fat is the most energy dense form of natural energy that the body can use. Sugar (a carbohydrate) and protein have 4 kcal per gram; fat has 9 kcal per gram. To that end our caveman would always devour fat when he came across it, not cast it aside due to health concerns!

Stored body fat is converted back into glucose (or ketones) when the body is in survival mode. It is not an easy process to start off in the body and uses up essential energy being stored for a time of scarcity. Your fat reserves are your main energy source when you dont have food to eat and will decide how long you can live without food.


Let’s look at meat (Protein source) which obviously comes from animals. Our caveman had to go out and hunt animals or fish in order to source essential nutrients such as protein, vitamins B-12 & D-3, Creatine and DHA which are not found in plants at all or in the case of protein in sufficient quantities.

These animals were difficult to hunt down and kill and required energy to be expended, but the pay offs were high due to the density of nutrients. Your body can use protein for energy but it does not like to do this as it is basically eating itself and breaking down muscles. This is bad and your body’s last ditch attempt at survival and to large extent decides when you are close to death how long you can live without food.

So what? How does this all affect survival?

This crash is because your blood glucose levels have spiked so quickly that your body overdoes the insulin which means not enough blood glucose; hence the lethargy. Glucose is burnt by the body very quickly, especially when the body is used to burning refined carbohydrate such as sugar (which the body has no biological function that requires you to consume it) And so the yo-yoing goes on. So where does that glucose go? Well, to keep things simple, your body stores it as fat; this is an evolutionary adaption for when food is scarce. If you have no food to eat the body will use its stored energy, which is stored body fat.

The clever amongst you will have realised that the modern diet of high carbs is bad for dieting and staying lean, but that is another argument for another day. High fat diets with low carb are absolutely essential for survival in the wilderness despite what Weight Watchers will tell you. It is simply to do with effort vs reward; finding sufficient carbohydrate to live on in the wild year round is very difficult. Meat has a high payoff vs effort due to the fat and nutrient dense organs that can be consumed and the fact that your body can store this fat and lengthen how long you can live without food.

So what How does this all affect survival

Blah blah blah… I still don’t get what this means?

Let me use a simple list of the order of preference that the body will use macronutrients.

1st – Carbohydrate
2nd – Fat
3rd – Protein

This means that during times of plenty the body will burn carbohydrate as an easy and ready main source of energy. When there is an excess it is stored for a less plentiful time, such as winter. When it comes to winter and there is little food, the body will then use fat as its main energy source. This is now eating into valuable reserves so the body will only do this when it has no carbohydrate energy source. Finally if your fat supply has been used and you have absolutely nothing else your body starts to break down protein (your own tissues) and use that. This is a final attempt at surviving and is normally the start of the onset of death and as I said earlier will dictate how long you can live without food being consumed.

So how long can you live without food?

Still with me? Good. The bottom line is here that most developed countries populations have ample fat stores to see them through quite a long period of no food. A pound of fat has 3,500 kcals; an adult male requires around 2,500 kcals per day if lightly active, a female around 2,000 kcals.
This means that even if you are lean with 6 pack abs (around 10% body fat for a man and 15 – 20% for a woman) you will still have around 20 pounds of fat = 70,000 kcals = 28 days of using 2,500 kcals or 56 days if you are carrying 40 pounds of fat. Unfortunately it’s not quite as simple as that as 30 – 40 days is around the longest you can live without food for various other reasons such as lack of vitamins, infection and organ damage etc.

To summarise everything in a nutshell – You can live for a long time without food so don’t stress too much if you don’t have it. You tummy will make some outrageous noises, but dry your eyes princess, you will be fine without food providing you have no underlying health issues.

I hope that that makes sense and you can see that food is way down the list of priorities and at the end of your PLWF list when you are in a survival situation. Before you go though, please have a look at my other articles as they have some great information in them.

Please share this post and comment below as I am always interested in what you have to say; good or bad.

5 thoughts on “How long can you live without food?”

  1. Hi Dave.

    This website looks great. I like the way you are able to simplify a relative confuseing subject. The flintstone stuff makes it more funny?
    I did not know that the body react this way when it has no carbohydrate source.
    Very informativ and userfriendly website!

    What do you think of Spirulina as a survival food supply?
    Is this stuff worth the money?



  2. Hmm….I prefer to have a food supply, or even more importantly know how to attain, hunt and gather food like our ancient forefathers did. But damn..I never knew our bodies could survive long without food, given that we don’t have health issues, which unfortunately forms am inority of the world population, most of us have health issues we’re not even aware of because they can seem to subtle at times.

  3. Interesting. Though I have read another study that concluded that our Paleolithic ancestors actually were not at the point of starvation all the time, since they supplemented their hunting with gathering of roots, berries, nuts, etc. which are often also the source of protein. They actually had more leisure time for social bonding within the group which was also essential for survival.

    That being said, I do agree with your message of the hardiness of the human race when it comes to survival without food. At times when our Paleolithic ancestors did face a crisis, because of natural disaster, conflict with other groups, and climate change, then they would have needed to go without. Sometimes hunters would come back empty handed, but I imagine that they’d still have roots, nuts, berries, and jerky on hand.

    Sorry for the long reply, this subject is a fascinating one to me.

    Good post by the way, very thought provoking.

  4. You’ve really made a complicated subject easy to understand. However, understanding it and putting it in to practice is quite often 2 separate things!

    You’ve enlightened me on one thing in particular, I thought fat was burned in the body first over carbs but obviously not! Recently meat has taken another hit in the UK media – about rare meat being a probable cause of cancer – there is always some type of meat, protein or dairy being blackened in the media!

    You’ve got a great site and really informative article here!

  5. Hi Dave,

    You have a great blog here. The information is important and not something that most poeple consider anymore. Most people just don’t think they will every be without food so they don’t know what might happen if they lose access to the grocery store.

    I enjoyed your entertaining presentation of the information while at the same time clearly explaining what your body needs whey it needs it and when.

    Thanks for the information and for a site to follow up with as you have new information available.


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