How Long Can You Live Without Food

There seems to be a gray area with regards to how long you can live without food. On one hand, you hear of people starving on a daily basis, collapsing after only a few days without nourishment. On the other hand, you hear of men and women who seem to survive for weeks without any type of food. It all depends on a variety of factors, which ultimately contribute to the amount of time you can survive without food. What's for certain, however, is that the body is incredibly designed to ensure that starvation is prevented at all costs.  

Why does the body need food?  Every animal on earth eats; it's a necessity to survive. An organism's body is constantly working, performing activities in the cells such as producing proteins, catalyzing substances that the body doesn't need, synthesizing enzymes and more. Unlike plants, we cannot produce out own source of carbohydrates, proteins or essential oils, which is why we must ingest food—to supply the body with energy.  

How does the body utilize food?  The human body is able to breakdown complex foods like meat, complex carbohydrates and plants through both mechanical and enzymatic digestion. The purpose is to break down these substances into basic molecules such as glucose, which are directly utilized by cells to preform cellular activities such as the production of ATP, the most potent source of cellular energy. Depending on and individual's metabolism, the rate at which the body utilizes food, a person will either burn all of the food up through cellular respiration or will convert the sugar into glycogen which leads to the buildup of fat.  

How long can you live without food? It is assumed that the average human being can live without food for roughly three to six weeks. At a glance, this may seem almost impossible, but in actuality it should not be surprising; the human body evolved to use energy efficiently. As a result, several factors ultimately play into this seemingly long period of time.  

• The body runs on food for days. An average person will take about two days to use up the total amount of energy from food in their system. After that, the body most find other sources of nourishment.
• The body stores energy for later use. After food resources have been exhausted, the brain sends chemical messages to the pancreas to secrete a hormone called glucagon, which breaks down glycogen (from fat) and increases the amount of sugar available to the cells.  
• The body is cannibalistic. When food and glycogen reserves are completely exhausted, the body will still be able to provide a source of energy for itself. In a process known as gluconeogensis, the body will actually begin to break down muscle tissue and convert it into glucose. After the body has used all of its muscle for energy, it leaves only an emaciated and malnourished individual who would eventually die because the body can't covert any more substances into energy.  

All in all, the human body is incredibly adaptive in terms of providing itself with energy.  When an individual does not have access to food, they will break down stored fat and eventually break down muscle due to gluconeogensis. This allows a person to go roughly a month without food, but that is assuming that they are drinking sufficient amounts of water.