How Long Can You Survive Without Food or Water?
Experts say it's incredible that the Thai soccer team survived as long as they did underground before the successful cave rescue operation.
More than two weeks after a dozen boys and their soccer coach went missing in Thailand, rescue efforts finally brought them safely out of the flooded cave they were found in on July 2. The group had gone to explore the Tham Luang caves in Chiang Rai on June 23 and were trapped after monsoon flooding caused the water levels in the cave to rise too high. Rescuers finally extracted the last team members, all of whom are alive, a feat in and of itself after surviving nearly nine days underground without food and fresh water.
It's a dramatic, terrifying tale that makes you wonder: Exactly how long can you go without food and water? Unfortunately, there's no exact answer. "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," explains Whitney Linsenmeyer, Ph.D., R.D., a spokesperson for the Academy of Nutrition and Dietetics and an instructor in the Department of Nutrition and Dietetics at Saint Louis University.
"In general, adults can go a few days (possibly up to a week) without fluids and a few weeks to about two months without food," says Liz Weinandy, a registered dietitian at The Ohio State University Wexner Medical Center. Because scientific studies on this topic would be unethical (this is starvation we're talking about), the information that's available comes from instances where humans are caught in natural disasters or situations like the one the Thai soccer team found themselves in, she says.
What's More Important: Food or Water?
Humans can generally last longer without food than without fluid. One study based on anecdotal reports and published in the journal Archiv Fur Kriminologie stated that humans can go without food or drink for eight to 21 days, but if someone is only deprived of food, they may survive for up to two months. And research published in the British Medical Journal used information from hunger strikes to determine that people can last 21 to 40 days without food before experiencing life-threatening symptoms.
But because your body is about 60 percent water, it's absolutely essential to your short-term survival to prioritize fluids. "Many organs in your body need enough fluid for proper hydration in order to function," says Weinandy. "Your brain, heart, lungs, kidneys, and muscles especially need enough water to work well. Once you start to get dehydrated, you're not able to think straight. That's not only due to fluid losses but also to the loss of important electrolytes like potassium and sodium, which are needed for proper muscle function-especially when it comes to your heart."
What Happens to Your Body When You're Not Getting Enough Food or Water?
Without the crucial nutrients from food and water, your body will start to move through metabolic changes known as the 'fed-fast cycle,' says Linsenmeyer. "The fed state typically lasts up to three hours following a meal; the postabsorptive state can last anywhere from three to 18 hours following a meal; the fasting state lasts from about 18 to 48 hours without additional food intake; the starvation state lasts from two days following a meal up to several weeks," she explains.
What that means is that when your body recognizes that it's not getting additional nourishment, it will start to adapt to your situation and use different sources as fuel. Most of the time, your body uses glucose for energy, but when those levels are depleted, "during the fasting state, the body's protein stores serve as a major energy source; during the starvation state, we see a metabolic fuel shift to using primarily fat stores in an effort to preserve lean body mass," says Linsenmeyer. (Interestingly, the keto diet is also known for shifting the go-to energy source from carbs to fat via ketosis. Does that mean the insanely popular keto diet is bad for you?)
Muscle actually stores more water than fat, explains Weinandy, which makes preserving that lean body mass important for someone entering starvation mode. But when you start to burn primarily fat for energy-a state called ketosis-that's when malnourishment becomes a major issue, because "there's no intake of vitamins, minerals, and electrolytes," she says. Your body can't store significant amounts of important nutrients like the B vitamins and vitamin C for more than a few days, and becoming deficient in them will affect your energy levels and overall health."
How Do You Know If You're Starving?
Of course, you'll be hungry-one of the first things the Thai boys said to their rescuers was "Eat, eat, eat, tell them we are hungry." But it's not just hunger pangs that can clue you into how dire your situation really is. "A lack of fluid will have the biggest effect on your body," says Weinandy. "You'll start to get dehydrated, and your blood pressure will drop due to a loss in blood volume as your body naturally tries to conserve water," which can eventually lead to strokes, heart attacks, and kidney failure. (Learn more about how dehydration affects your mind and body.)
"When the human body is in starvation mode and/or prolonged dehydration, symptoms also include a slowed metabolic rate, breakdown of the body's protein stores, hormonal imbalances, fatigue, severe headaches, dizziness, seizures, confusion, and difficulty concentrating, says Linsenmeyer.
That study from BMJ also reported that the main disabling symptom during starvation mode is feeling faint and dizzy, and, in almost all cases, they also found people to have abnormally low heart rates, thyroid issues, abdominal pain, and depression.
How to Survive Without Food or Water
While most things are out of your control if you find yourself trapped in, say, a flooded cave, there are a few things that could help you survive longer.
Most importantly, you want to minimize physical activity. "An individual's basal metabolism is the energy required to maintain normal body functioning, i.e. brain function and respiration," says Linsenmeyer. "Any physical activity requires additional energy beyond one's basal metabolism, so, in theory, minimizing physical activity would reduce one's total energy needs," which would help your body conserve energy when it's not receiving any additional energy from food or water.
You'll also want to keep as cool as possible, whether that means literally finding a cool spot to wait for rescue or just keeping yourself from sweating. "We lose water through urine, sweat, and breathing, so it is impossible to conserve it all-but our bodies will try to lessen the amount that leaves," says Weinandy, and anything you can do to help your body do that will help your survival.