Most people can survive without food for at least a few weeks, maybe a bit longer. Eventually, however, starvation kills.

Yet the limits on how long people can go without eating are complicated; without water people are unlikely to last a week, but the amount of time starvation takes can vary drastically.

Take the story of Angus Barbieri. For 382 days, ending July 11, 1966, the then-27-year-old Scotsman ate nothing.

There’s limited documentation of Barbieri’s fast: there are a few old newspaper stories recounting his ordeal and more convincingly, there’s a case report describing the experience that his doctors published in the Postgraduate Medical Journal in 1973.

According to that report, Barbieri had walked into the University Department of Medicine at the Royal Infirmary of Dundee, Scotland, more than a year before, looking for help. He was “grossly obese” at the time, according to his doctors, weighing 456 pounds. The doctors put him on a short fast, thinking it would help him lose some weight, though they didn’t expect him to keep it off.

But as days without food turned into weeks, Barbieri felt eager to continue the program. Absurd and risky as his goal sounded – fasts over 40 days were and still are considered dangerous – he wanted to reach his “ideal weight,” 180 pounds. So he kept going.

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In what was a surprise to his doctors, he lived his daily life mostly from home during the fast, coming into the hospital for frequent checkups and overnight stays. Regular blood-sugar tests – intended to demonstrate that he was somehow able to function while very hypoglycemic – assured doctors that he really wasn’t eating. Weeks turned into months.

Barbieri took vitamins on various occasions throughout the fast, including potassium and sodium supplements. He was allowed to drink coffee, tea, and sparkling water, all of which are naturally calorie-free. He said there was the occasional time that he’d have a touch of sugar or milk in tea, especially in his final few weeks of fasting.

At the end of his ordeal, Barbieri tipped the scales at 180. Five years later, he’d still kept almost all the weight he’d lost off, weighing in at 196.

The limits of the human body

The Scotsman’s fast is perhaps the most extreme example of a starvation diet ever recorded. (At least one person has reportedly even gone longer without food than Barbieri; a man named Dennis Galer Goodwin lasted 385 days on a hunger strike to assert his innocence of a rape charge before he was force-fed through a tube.)

But Barbieri’s extreme regimen is not the only fast for health of eye-popping duration. In 1964, researchers published a study noting that “prolonged starvation” could be an effective treatment for severe obesity, with at least one patient fasting for 117 days. For medical reasons, several others have exceeded the 200-day fasting mark, though there has been at least one death during the refeeding period for one of those patients.

In a sense, these stories show the body’s remarkable ability to (in a few rare cases) survive off of its own fat stores, provided those stores are excessive enough in the first place. Still, make no mistake, these types of extreme diets can be deadly. No one can survive without energy, which comes from food and can come from fat stores, though only for a period of time.

While “starvation” as a treatment enjoyed some popularity in the 1960s and 70s, doctors abandoned this strategy because it was likely to kill patients. After a certain period of time the body burns through fat and muscle, eventually causing physical changes that drastically increase the chance of a fatal heart attack. Even low-calorie diets that provide insufficient nutrition have killed, with autopsy reports showing the characteristic signs of starvation.

But as Barbieri shows, the question of how long people can live without food is a complicated one.

Before his first meal after the fast, he claimed to have forgotten the taste of food. For breakfast on that July morning, he then ate a boiled egg, a slice of bread with butter, and a cup of black coffee.

According to a report published in the Chicago Tribune, the next day he told a reporter, “I thoroly [sic] enjoyed my egg and I feel very full.”

For more on this story and for an in-depth look at the wild science of fasting, check out our feature investigating the practice.