How Long Can You Live Without Food?

Without water you can only survive for a few days. You may be able to live for weeks without food, though.

This is because your body is very resourceful. It can obtain energy and fuel from its own fat. If needed, it can also use muscle stores.

Still, the timeframe for survival without food is not exact. There is no robust scientific data available to answer this question. That's because ethics prevent scientists from studying starving people.

Every person is different. Personal factors like starting weight can play a role. This is why it can be hard to answer this question.

This article discusses the question of how long you can survive without food. It also discusses some of the complications that can happen when you don't eat.

How the Body Fights Starvation

Your body normally uses glucose, or sugar, as its main source of energy. When you don't eat, your glucose reserves are used up within one day.

After one day without food, your body releases a hormone called glucagon. This hormone tells your liver to make glucose. This glucose is used mostly to feed your brain.

After two or three days, your body starts to break down fatty tissue. Your muscles use the fatty acids created during this process as their main source of fuel.

Fatty acids are also used to form ketones in the liver. Ketones are another substance the body can use for energy. These are released into the bloodstream. When the brain uses them for fuel, it doesn't need as much glucose.

When the fatty acid reserves are gone, the body switches to protein. It gets protein by breaking down muscles. As this breakdown speeds up, the body begins to lose heart, kidney, and liver function. This is what ultimately leads to death.

What Influences Survival

There are only limited studies into how long people can live without eating. Many look at people who chose to starve themselves and were later evaluated by a doctor.

Based on these studies, there appear to be a few factors that influence how long a person can live without food.

One factor is a person's starting weight. People who are lean can usually tolerate a loss of up to 18% of their body mass. People who are obese can tolerate more, possibly over 20%.

Other factors may play a role in survival time. These include:

• Gender: Females survive longer than males. This is true even in famines.
• Age: Children are at higher risk of death during famines.

Complications From Lack of Food

Unless eating is resumed, starvation always leads to death. Before death, certain complications may occur. The number of body systems affected increases as weight loss increases.

Some of these complications include:

• Bone loss
• Muscle weakness and wasting
• Feeling cold
• Thinning or loss of hair
• Dry skin
• Constipation
• In females, loss of menstruation
• Fatigue, shortness of breath, and paleness from anemia, a lack of oxygen-carrying red blood cells

Summary

The length of time human beings can survive without food is an open question. No studies can be done on this subject, and the answer depends on individual factors like starting weight.

The body fights starvation by producing glucose and breaking down fatty tissue. In later stages of starvation, it breaks down muscle. 

Starving people become weak in 30 to 50 days. Without food, they usually die in 43 to 70 days.

Starvation always leads to death. Before death, there may be symptoms like bone loss, muscle wasting, and fatigue.

A Word From Verywell

Most people who ask this question are simply curious. For example, you may have heard a rescue story that made you wonder "what if?"

If you are restricting your food intake, though, your concern is very real. An eating disorder like anorexia or a very strict diet can have serious health consequences. If this describes you, please seek medical help at once. You deserve the food your body needs to thrive and function.