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.
Why the time period varies
Eliminating food and water intake for a significant period of time is also known as starvation. Your body can be subject to starvation after a day or two without food or water. At that time, the body starts functioning differently to reduce the amount of energy it burns. Eventually, starvation leads to death.
There is no hard and fast “rule of thumb” for how long you can live without food. There’s a lack of scientific research on starvation because it’s now considered unethical to study starvation in human subjects.
There are some studies that explore old research on starvation, as well as examine more recent occurrences of starvation in the real world. These instances include hunger strikes, religious fasts, and other situations.
These studies have uncovered several observations about starvation:
- An article in Archiv Fur Kriminologie states the body can survive for 8 to 21 days without food and water and up to two months if there’s access to an adequate water intake.
- Modern-day hunger strikes have provided insight into starvation. One study in the British Medical Journal cited several hunger strikes that ended after 21 to 40 days. These hunger strikes ended because of the severe, life-threatening symptoms the participants were experiencing.
- There seems to be a certain “minimum” number on the body mass index (BMI) scale for survival. According to the journal Nutrition, men with a BMI of less than 13 and women with a BMI of less than 11 cannot sustain life.
- An article in the British Medical Journal concludes that those who are of a normal weight will lose a higher percentage of their body weight and muscle tissue faster than those who are obese when starving during the first three days.
- According to the journal Nutrition, women’s body composition makes them able to withstand starvation longer.
How is this possible?
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. This allows people to engage in religious fasts and even try “fasting” diets like the eat-stop-eat approach without doing irreparable damage to their bodies.
It takes about eight hours without eating for your body to change how it operates. Before that, it functions as if you were eating regularly.
Under normal circumstances, your body breaks down food into glucose. The glucose provides energy to the body.
Once the body hasn’t had access to food for 8 to 12 hours, your glucose storage is depleted. Your body will begin to convert glycogen from your liver and muscles into glucose.
After your glucose and glycogen are depleted, your body will begin to use amino acids to provide energy. This process will affect your muscles and can carry your body along for about three days of starvation before metabolism makes a major shift to preserve lean body tissue.
To prevent excessive muscle loss, the body begins to rely on fat stores to create ketones for energy, a process known as ketosis. You will experience significant weight loss during this time. One of the reasons women are able to sustain starvation longer than men is that their bodies have a higher fat composition. Females are also able to hold on to protein and lean muscle tissue better than males during starvation.
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 percent of their body weight. It also says that very serious conditions will occur when an individual loses 18 percent of their body weight.
Why does water intake affect this?
You’re much more likely to survive starvation for weeks — and possibly months — if you’re able to consume a healthy amount of water. Your body has much more in its reserves to replace food than fluid. Your kidney function will diminish within a few days without proper hydration.
According to one article, those on their deathbeds can survive between 10 and 14 days without food and water. Some longer periods of survival have been noted, but are less common. Keep in mind that people who are bedridden aren’t using much energy. A person who is healthy and mobile would likely perish much sooner.
One study that looked at hunger strikes suggested that a person needs to drink at least 1.5 liters of water a day to survive starvation for a longer period of time. The study also suggested adding a half teaspoon of salt a day to the water to help with kidney function.
Side effects and risks of restricted eating
Living without access to food and water can have detrimental effects on your body. Your body’s many systems will begin to deteriorate despite your body’s ability to continue for days and weeks without food and water.
Some of the side effects of starvation include:
- blood pressure drop
- slowing heart rate
- thyroid malfunction
- abdominal pain
- low potassium
- body temperature fluctuation
- post-traumatic stress or depression
- heart attack
- organ failure
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, including:
- heart conditions
- neurological conditions
- swelling of the body’s tissue
Resuming eating after starvation will require a doctor’s supervision and may involve eating boiled vegetables, lactose-free foods, and a low-protein, low-sugar diet.
The bottom line
Human bodies are fairly resilient and can function for days and weeks without proper food and water. This isn’t to say that going without food for a prolonged period is healthy or should be practiced.
Your body can maintain itself for a week or two without access to food and water and possibly even longer if you consume water. Those who experience starvation will need to be monitored by a doctor to get back to health following the time period without nourishment to avoid referring syndrome.