Experts do not know exactly how long a person can live without eating, but there are records of people surviving without food or drink between 8 and 21 days.

Estimates of how long you can live without food are based on events where people have survived being trapped or buried alive, as it is not ethical to carry out such experiments on humans.

The length of time a person can survive without any food or water will depend on various factors, such as the individual’s age and health and whether or not they have anything else to drink.

Food and water consumption is essential to human life. Your body needs energy from food sources and hydration from water to function properly. The many systems in your body work optimally with a varied diet and adequate water intake daily.

But our bodies are also able to survive for days without water. We can go days or sometimes weeks without food because of adjustments to our metabolism and energy consumption.

When a person’s body does not receive enough calories to carry out its usual life-supporting functions, this is known as starvation. This can happen if food intake is severely restricted, or if a person’s body cannot digest food to absorb nutrients.

When the human body is severely deprived of calories, it starts functioning differently to reduce the amount of energy it burns. If nutrition is not restored, starvation leads to loss of life.

There is no hard and fast “rule of thumb” for how long you can live without food. To some extent, the answer depends on individual differences and circumstances. Information about life expectancy is based on real world contexts, such as hunger strikes and serious medical conditions.

With no food and no water, the maximum time the body can survive is thought to be about one week. With water only, but no food, survival time may extend up to 2 to 3 months.

Over time, a severely restricted food intake can reduce the lifespan.

Being underweight, defined as having a body mass index (BMI) below 18.5, is associated with malnutrition and a range of health conditions that can lower life expectancy. These include reduced immune system function, digestive conditions, and cancer.

A 2018 study found that having a BMI below 18.5 could shorten your life by an average of 4.3 years for males and 4.5 for females.

Being able to live for days and weeks with no food and water seems inconceivable to many of us. After all, a daylong fast or even an hours-long stretch without food and water can make many of us irritable and low on energy.

Your body actually adjusts itself if you engage in a short-term fast or are unable to access food and water for very long stretches of time.

For this reason, adults without health conditions are usually able to engage in religious fasts and even try “fasting” diets like the eat-stop-eat approach while continuing their regular daily activities.

It takes about 24 hours without eating for your body to change how it produces energy.

Under normal circumstances, your body breaks down food into glucose. The glucose provides energy to the body.

During the first 24 hours without food, as your glucose storage is depleted, your body will begin to convert glycogen from your liver and muscles into glucose.

By the second day without food, your glucose and glycogen are depleted. Your body will begin to break down muscle tissue to provide energy. However, your body is designed to conserve muscle, not break it down. So this phase provides temporary energy while your metabolism is making a major shift.

To prevent excessive muscle loss, the body begins to rely on fat stores to create ketones for energy, a process known as ketosis.

During the first 5 days without food, a person may lose 1–2 kilograms (2.2–4.4 pounds) of body weight each day. Most of this weight loss is related to dehydration and electrolyte imbalance. Over several weeks of starvation, changes in the body usually cause weight loss to slow down to an average of 0.3 kilograms (0.7 pounds) per day.

The more fat stores available, the longer a person can typically survive during starvation. Once the fat stores have been completely metabolized, the body then reverts back to muscle breakdown for energy, since it’s the only remaining fuel source in the body.

You’ll begin to experience severe adverse symptoms during the stage of starvation where your body is using its muscle reserves for energy.

A study in the British Medical Journal states that those undergoing a hunger strike should be monitored closely for severe side effects of starvation after losing 10% of their body weight or has a BMI of 16.5 or less. It also says that very serious conditions will occur when an individual loses 18% of their body weight.

With adequate water intake, some people have survived with no food for weeks or even several months. Survival time is longer with water intake because the body has much more in its reserves to replace food than fluid. Your kidney function will diminish within a few days without proper hydration.

One 1997 commentary that looked at hunger strikes suggested that a person needs to drink about 1.5 liters of water a day to survive starvation for a longer period of time. The author also suggested adding up to half a teaspoon of salt a day to the water.

Depending on the specifics, reports suggest that some people can survive starvation for days or weeks. However, during starvation, your body’s many systems will begin to deteriorate.

The effects of starvation may include:

People who have experienced starvation or very restricted food intake may have long-term effects including:

  • stunted growth
  • poor bone health or osteoporosis
  • post-traumatic stress or depression

Those who experience starvation for a prolonged time can’t begin to consume normal amounts of food right away. The body needs to be very slowly eased in to eating again to avoid adverse reactions, known as refeeding syndrome. The effects of refeeding syndrome may include:

  • heart conditions
  • neurological conditions
  • swelling
  • electrolyte imbalances

To reintroduce food safely, people who have experienced starvation or malnourishment need to be cared for in a hospital or specialized medical facility.

How long can you go without eating?

Estimates based on events when people have been trapped or buried suggest you can survive without food between 8 and 21 days. In 1981, hunger strikers in the Maze Prison, Belfast, died after 45–61 days of not eating food.

What happens if you don’t eat for 7 days but drink water?

During the first 5 days of not eating any food, a person may lose 2.2–4.4 pounds per day. If you don’t eat for 4 days you may also experience faintness and dizziness. Once a person loses 10% of their body weight or has a BMI of 16.5 or less, complications due to starvation may begin. Experts commenting on hunger strikes recommend close observation after 10 days of not eating if a person’s original body weight is unknown.

Can a person live 30 days without food?

Yes, it’s possible someone may live 30 days without food, although very unlikely. Some records suggest people have survived up to 61 days, although usually, most live 8 to 21 days.

Why does hospice stop giving food and water?

Hospice care doesn’t typically deny food or water to a person who requests either. However, as the body prepares to die, it is common that the need or desire for food and drinks declines. It’s also possible that when death is near, eating may be uncomfortable and could lead to complications that may make dying a longer and painful process. If you have any concerns about a loved one who is receiving palliative care, consider discussing those with them, if possible, and their care team.

Human bodies are fairly resilient. In some circumstances, the body can function for days or weeks without proper food and water, but there are risks.

People who have experienced starvation may have long-term health effects, and starvation eventually becomes fatal.

People who have experienced starvation or malnourishment will need medical treatment and close monitoring by a medical team to avoid refeeding syndrome.