How Long Can You Survive Without Food?

Written by , MSc (Biotechnology), ISSA Certified Fitness Nutritionist Charushila Biswas MSc (Biotechnology), ISSA Certified Fitness Nutritionist Experience: 6 years

It is one thing to fast. And another to starve. The recent heart-wrenching rescue story of the soccer team boys and their coach who were trapped in a cave in Thailand for nine days without food or fresh water is a horrifying yet typical example of starvation. Political leaders, like Mahatma Gandhi, had gone on several hunger strikes to restore peace and unity.

Time and again, it has been proven that humans can survive without food for a certain period. But, stretching that period can be life-threatening. What’s the threshold? For how long can you survive without food? What happens to your body when you don’t eat for a prolonged period? What are the psychological impacts? Keep reading to find out all about that.

How Long Can You Survive Without Food?

Humans can survive without food for about 8-21 days (1). According to Whitney Linsenmeyer, Ph.D., RD, “Survival time would depend on various factors such as initial hydration state, body size, lean body mass, fat mass, metabolic rate, and any physical activity.”

For ethical reasons, the effects of starvation on human subjects have not been studied. The only information we have on how long humans can survive without food is from various hunger strikes and famines. Whether it is self-imposed or forced (war-time tortures), the starvation threshold differs from person to person.

For example, in 1981, members of the Irish Republican Army (IRA), imprisoned in England, went on a hunger strike led by the IRA commanding officer, Bobby Sands. The prisoners drank small amounts of water but did not consume any food. Sands died on the 66th day. Thomas McElwee was the longest to survive the hunger strike (73 days).

This brings us to the next question. Why does the time vary? Let’s find out.

Why Does The Surviving Time Vary?

Why Does The Surviving Time Vary
Image: Shutterstock

The number varies because a number of factors – like body composition, metabolic rate, availability of water, activity levels, and BMI – play a major role.

For instance, women have more fat in their body compared to men. Hence, women have more chances of surviving longer than men while starving (2).

In fact, an individual with normal weight loses body weight and muscle mass faster than an obese individual while starving (3).

Men with a BMI less than 13 and women with a BMI less than 11 cannot survive life (2).

Water also plays a crucial role in survival time. Let’s find out how water helps in survival during a period of prolonged starvation.

How Does Water Intake Affect Starvation?

Consuming a healthy amount of water while starving can increase your chances of survival. In fact, without a drop of water, you might not stand a chance of surviving at all!

Consume at least 1.5 liters of water with a pinch of salt to keep your kidneys and other organs functioning properly.

To understand the effect of starvation, you’ve got to understand what happens to the body when you are starving. Find all about it in the next section.

What Happens To Your Body When You Starve?

What Happens To Your Body When You Starve
Image: Shutterstock

When you starve, i.e., you have not eaten for 8 hours or more, your body’s glucose stores get depleted. The body starts to convert muscle glycogen into glucose for fuel.

After the muscle glycogen is used up, your body starts to break proteins into smaller units called amino acids. Then, the amino acids are used to synthesize glucose through a biological pathway called gluconeogenesis. The glucose is then used to fuel the body.

Finally, when there are no other options available, the body starts to use fat as a source of fuel. So, the more fat you’ve got, the better the chances of you surviving a prolonged period without food.

In about three days, your metabolism shifts to the “famine mode.” Your metabolism slows down to preserve the fuel sources so that you can survive without food. It might seem like good news – but it’s not. Here’s what else can happen when you starve for too long.

Other Effects Of Starvation On The Body

  • Thyroid malfunction
  • Dizziness
  • Stomach ache
  • Low potassium levels
  • Fluctuation in body temperature
  • Weakness
  • Dehydration
  • Slow heart rate
  • Blood pressure drop
  • Organ failure
  • Heart attack
  • Muscle spasms
  • Convulsions
  • Osteoporosis
  • Repeated vomiting

Starving can also affect your psychology. Here’s what may happen.

Psychological Effects Of Starvation

  • Depression
  • PTSD (Post-Traumatic Stress Disorder)
  • Hallucinations
  • Restricted thinking
  • Anxiety
  • Diminished cognitive ability

This brings us to one burning question, a concern that needs to be addressed in the scope of this article – should you starve to lose weight?

Should You Starve To Lose Weight?

Never! Do not starve to lose weight. The “famine mode” that your metabolism shifts to may cause you to gain weight instead of helping you to lose it. The famine mode causes your metabolism to slow down, and whatever you eat will get stored as fat.

Moreover, there are other ways to lose weight. There are other quick weight loss ways that you can follow for an upcoming event. I highly recommend changing your lifestyle so that you are always fit and don’t have to look for ways to lose weight quickly.


Survival is coded in our genes. That’s why the kids and their coach, who were trapped in the Thailand cave, were able to survive without food or drinking water. But, using it as a means to lose weight should never be practiced. Even politicians prepare for a week or two before going on a hunger strike – and they are constantly monitored by doctors.

Let us know your thoughts about survival without food in the comments section below. Take care!


  1. Survival time without food and drink” Archiv für Kriminologie, US National Library of Medicine.
  2. The biology of human starvation: some new insights” British Nutrition Foundation.
  3. Weight loss will be much faster in lean than in obese hunger strikers” British Medical Journal, US National Library of Medicine.
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Charushila Biswas

Charushila BiswasHealth & Wellness Writer

Charushila is an ISSA certified Fitness Nutritionist and a Physical Exercise Therapist. Over a span of 6 years, she has authored more than 400 articles on diet, lifestyle, exercises, healthy food, and fitness equipment. She strives to inform, educate, and motivate her readers via authentic, straightforward, and fact-checked information. After completing her master's in biotechnology from Vellore Institute of Technology, full bio