There is actually no fixed period of time for how long you can live without food. Unlike water, which you can’t survive without for no more than a couple of days, you can survive without food for weeks, months, and in some circumstances over a year. These are extreme examples though, and so in this post I’ll go over how long the average person can go without food, and show you the longest someone has gone without food before.
‘Without food’ generally means that you can have supplements and water – just nothing to eat. To some, having supplements might seem like cheating, but you will see below examples of people not taking any supplements too.
With the use of supplements and water, the cause of death will be from a lack of energy to perform essential biological functions, not from nutritional deficiencies. The amount of energy in the body can be estimated by calculated from the energy stores that are in the body. First, we can look at glycogen, which is a short/ medium term energy supply.
The average healthy well fed adult can store approximately 2000kcals of glycogen in their body, which equates to just over 1 days worth of energy for most people (assuming that very little exercise is being done).
You can then look at the amount of fat stores in the body. This will vary from person to person, however, a healthy male will have around 15% of their body mass as fat. Going with the average weight of a male being 70kg, this would give them about 11.25kg of total fat on their body.
However, not all this body fat can be used as energy – the body actually needs some a fat for insulation/ protection of organs etc. There is some discrepancy as to how much body fat the body will retain at all costs, but for the purposes of this calculation, we can say 2% of their body mass. This would give 9.1kg of fat which can be used for energy.
9.1kg of fat equates to 81900kcals (1g of fat being 9kcals). This would give someone an extra 43 days worth of sedentary living. So, by these rough calculations of the amount of energy the body can store, a healthy average person could live for about 40- 45 days.
Obviously due to the nature of the question, experiments cannot be conducted to find the answer – that would be very cruel and illegal. However, there have been some well documented incidences where people on hunger strikes have survived up to 40 days, which offers support to the 40-45 day estimate and suggests it is quite accurate. These people on hunger strikes would probably not have been taking nutritional supplements, which suggests this limit is both an energy and a nutritional limit for the body.
A 27-year old man has gone for a massive 382 days without eating food. He was obese, taking a multivitamin, and had close medical supervision, but it is still an impressive feat. This goes to show how much of a limiting factor energy is when it comes to survival.
The body needs energy and micro-nutrients from to survive – take food away, and the body will slowly start to ‘fall apart’. Biological functions will become less efficient until they can no longer go on due to lack of energy/ essential micro-nutrients. Assuming you can source energy from your own large fat stores, and micro-nutrients from a pill, you can go on for a long period of time (until your energy stores run out in fact). The record for this has been 382 days, but for most people, this is not achievable.
For the average person, it would appear from the limited data that you can survive approximately 40 days without food (as a result of energy and nutritional deficiencies), but signs of malnutrition will manifest much earlier than that.
Image courtesy of Christina Hendricks
The average person can survive for up to a maximin of 45 days, but many won’t live this long. The longest someone has gone without food is 382 days.