In 1965, a 27-year-old man turned up to a Scottish hospital with a strange request. The man, who weighed 207kg (around 32 stone) was giving up food – and he wanted the doctors to monitor his body along the way.

The fast was never meant to last longer than a month or so, but he seemed to adapt well and the doctors allowed him to continue under careful supervision. For 382 days, he ate nothing but vitamin pills and other nutrients to stabilise his metabolism. By the end, he was a far healthier 80kg (around 13 stone) – with the doctors reporting that he had managed to maintain that weight for at least another five years after he had returned to eating normally again.

As crash diets go, this has to be the most extreme – and it certainly would not be advisable for anyone to repeat. But his story does help us answer some interesting questions. How much energy do we store in fat? What nutrients are crucial for our short- and long-term survival? And does regular, moderate fasting – such as the popular “5:2 diet” – have any health benefits?

Our colleagues at BritLab look at the hard science for some answers, while busting some myths along the way. Watch the video below to find out more.

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