A lot is made of the weird and wonderful things millionaire biohacker Bryan Johnson does to reverse the aging process.
He's hit the headlines for things like undergoing plasma transfusions from his son - but why is he going to such great lengths?
Johnson, 46, has opened up about why he wants to slow down the aging process in a YouTube video, talking through his journey.
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"The people who I admire the most did things typically over a multi-decade timeframe," Johnson said in the video - and when he hit 34, he realized it was "time to try and do something meaningful on that multi-decade timescale".
Johnson suggested he broke the world record in age reversal in 2022, when he reversed his epigenetic age by 5.1 years in seven months (FYI, epigenetic age relates to the biomarkers in your body that suggest your age, and is often different to what your birthday might say).
In 2021 Johnson started following Blueprint, what he calls 'an algorithm that takes better care of me than I can myself'. After two years of this, he says he's slowed the pace of aging by the equivalent of 31 years - and he's sharing all his data online.
Part of his success, he said in the YouTube video, is from thinking about "the body in its entirety".
He said: "You have to really think about it from a holistic perspective, so it's the common things like diet and exercise, but it's also a much broader consideration."
The result? "It's produced near-perfect health for me," Johnson said.
That might be so, but his youth-chasing efforts don't exactly sound like a laugh a minute.
Johnson works out for at least an hour a day, blends much of his food before eating it, never touches junk food and apparently goes to sleep at 8.30 pm every night - having eaten his last meal of the day at 11am.
And of course, all of his wild efforts cost money - Johnson reportedly forks out $2 million (£1.59 million) a year for his anti-aging crusade... but he's got money in the bank.
Johnson sold his payment processing tech business, Braintree, to PayPal a decade ago - with Johnson saying he made $300 million from it.
The biohacker seems to be aware of all the fuss he's stirred up on the internet - but he's not particularly bothered by what people are saying about him.
He said: "No matter how extreme I've had to be, no matter how eccentric people perceive me to be because I'm outside the norms, demonstrating that age can be arrested would change everything."