Stories occasionally appear in the news of people surviving surprising lengths of time without food. Many of these stories are hard to believe because the effects of fasting are so readily apparent after just a few hours. They also drive the question of how long a person can live without access to food.
Under traditional circumstances, our bodies break food down into glucose, which provides energy to the body. After eight to 12 hours without food, the body burns through its glucose reserves and begins to convert glycogen from the liver and muscles into glucose. After two or three days of fasting, the liver synthesizes ketone bodies for fuel by breaking down fat stores. Eventually, all cells in the body break down proteins into amino acids, which the liver then turns into glucose. If fasting continues, the body preserves lean body tissue and tries to balance its fat consumption. Once there is no more fat, the body returns to metabolizing muscle because it is the only remaining energy source.
Because of the various ethical issues surrounding studying starvation, much about the topic remains unknown. Additionally, the limit changes depending on a person’s percentage of body fat and general health. This means that researchers and experts cannot accurately say how long a person can go without food. A few medical studies estimate that complete starvation leads to death within 12 weeks, while others set a maximum of a couple of months. However, starvation also causes many other potentially fatal issues, such as liver or heart failure.
A few individuals have attempted to test how long they can safely go without food. In 2003, illusionist David Blaine locked himself in an acrylic glass box and spent 44 days without food. He received water through a small tube. After the 44 days, he had lost around 60 pounds and was experiencing the classic symptoms of starvation: loss of body mass, breathing issues, and heart palpitations. Historically, various individuals practiced professional fasting. The most well-known of these individuals is Henry Tanner, who allegedly survived fasting for 40 days under medical supervision.
Perhaps the most significant sources of information on the effects and limits of starvation are the various hunger strikes that have occurred throughout history. Mahatma Gandhi’s 21-day fasts are famous, but some individuals went further. Hunger strikers of Maze Prison in Belfast died after 45 to 61 days without food. Terence MacSwiney was an Irish author and politician who protested his prison sentence with a hunger strike. After 68 days without food, he fell into a coma. He died five days later, marking 73 days.
Because hunger strikes provide such valuable information, researchers regularly use them as reference points. One study suggests that medical professionals monitor hunger strikers after 10% weight loss in lean, healthy individuals. Significant issues begin at 18% weight loss. Most hunger strikers have orthostatic hypotension by day 20, with serious problems arising soon after.
Experts have noted a few key differences in how male and female bodies respond to starvation. Females appear to withstand starvation much better than males, even at lower BMI values. Some researchers believe this is due to females having greater amounts of adipose tissue. Additionally, female bodies may naturally prefer using fat, rather than lean tissue, for energy during starvation.
People in persistent vegetative states often live for 10 to 14 days after the removal of artificial sustenance. Because they are comatose, they are consuming the lowest possible amount of calories. Individuals who are healthy and active will burn calories at a much higher rate, significantly decreasing their survival time without food.
A person can dramatically increase how long they survive without food by hydrating themselves. One popular study claims that a person can only live up to 21 days without food or fluids. However, this increases to two months if they have a fluid source. Some experts believe that an individual must drink at least six cups of water a day to endure starvation.
The more fat stores a person has, the longer they can go without eating. This means that people with higher BMIs are more likely to survive for longer periods. After studying people who died of starvation, famine, or anorexia nervosa, researchers were able to approximate the human body’s limit using BMI. They found that a BMI of around 13 is fatal in males, while females have a lower limit of 12. Because various other factors affect BMI, these numbers are largely referential rather than definite limits.
Starvation is often not the direct cause of death, even though it is the trigger. Most people who experience starvation die of cardiac arrhythmia or cardiac arrest resulting from degrading tissues and electrolyte imbalances. Because of this, a person may not survive starvation even if they again begin receiving food. Eating after starvation can trigger problems such as Wernicke encephalopathy and hypokalemia. These may then lead to cardiac issues and death.
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