How long can a person last without food or water

Researchers believe that a person can live for up to three weeks without food as long as they have water to drink. Without both water and food, a person cannot survive for more than four days.

The body often finds alternate ways to generate energy during starvation and prolong life. However, in the absence of water, the body undergoes several changes and severe dehydration, and the kidneys may shut down.

The timescale for survival in the absence of food remains questionable. Aside from the fact that there is no solid scientific evidence to address this topic, researchers could never intentionally starve study participants to investigate the time frame of death due to starvation because of ethical considerations. Each individual is unique, and personal characteristics such as body weight, genetics, and comorbidities play a role.

In rare cases, such as Mahatma Gandhi’s hunger strike in the 1940s, Gandhi stopped eating and only drank sips of water for 21 days. Though he suffered a severe decrease in body mass, he survived. Throughout his life, Gandhi is said to have participated in 14 hunger strikes for extended periods of time.

The body runs on the energy provided by the calories in the food we eat. When you stop eating, your body starts to break down its own tissues for food, disrupting all the vital processes of your systems. This results in severe weight loss and leads to organ failure.

Here’s what happens to the human body during starvation:

Central nervous system

• The brain usually takes up to one-fifth of the total energy the body consumes in a day.
• During starvation, the brain gets deprived of this energy which affects the way it functions and may lead to trouble concentrating and sleep problems.

Cardiovascular system

• During starvation, energy levels decrease and affect the way the heart works.
• Due to the lack of energy, the heart cannot pump blood across the body as effectively as it should, leading to a decrease in blood pressure and pulse.
• Initially, there is low blood pressure and a low pulse, and then eventually the heart fails.

Gastrointestinal system

• Decreased food intake affects digestion and emptying of food in the stomach, leading to bloating, nausea, vomiting, a decrease in blood sugar levels, and constipation.
• In the long term, the muscles in the digestive tract weaken and may lose the strength to push the food forward through the gut.
• Starvation may lead to severe complications, such as pancreatitis (inflammation and swelling of the pancreas) that causes severe stomach pain, nausea, and vomiting.

Endocrine system

• To produce hormones, the endocrine organs need dietary fat and cholesterol. In the absence of food, the body cannot produce hormones such as testosterone, estrogen, and thyroid hormones, leading to:

To protect the body from hypothermia during starvation, the body produces a feathery covering of hair called lanugo that keeps the body warm.

Ketosis is the body’s mechanism to produce energy by burning the stored fat instead of carbs. Ketone bodies are the main sources of energy to the brain in the absence of glucose, and they preserve brain functions during starvation.

During three days of starvation, the brain gets 20 percent of energy from ketones, and this number increases to about 60 percent during prolonged starvation.

The Ketogenic diet utilizes the principle of ketosis to lose weight. However, followers of the diet eat foods rich in calories, such as protein, as opposed to stopping eating entirely.

Usually, a person may survive only for three days without water, but this may change depending on the person’s body needs. No one can live more than five to six days without water.

The human body undergoes the following changes during dehydration:

Brain damage

• Dehydration reduces energy levels in the body and makes us more irritable.
• Brain functions are impaired, and we lose the ability to perform basic tasks.
• The brain may even shrink temporarily if we don’t drink water.

Dark-colored urine

• When your body is dehydrated, the brain signals the kidneys to retain extra water in the blood instead of flushing it through urine. When the blood retains water, the urine becomes very concentrated and turns dark yellow with a strong odor. This is your body's method of saving water.

Hunger

• Dehydration makes us feel hungry although we just ate, making us eat more. Dehydration and hunger are often confused.

Headache

• We will develop headaches if we don't drink enough water because the brain puts double effort to perform basic bodily functions when we are dehydrated.
• Lack of water makes the eyes go dry, and eventually, they start to ache.

Slow death

• Along with experiencing the above symptoms, if we go on without drinking water, our organs, especially the brain, begin to shut down, leading to serious effects such as fainting, stroke, and toxin buildup.
• We may die after three to five days without having water.

Medically Reviewed on 7/5/2022

Image Source: Lemuel Caparaz / Getty Images Why is Dehydration so Dangerous? https://rehydrate.org/dehydration/

How Long Can a Person Survive without Food? https://www.scientificamerican.com/article/how-long-can-a-person-survive-without-food/