Who wants to live to 100 on a diet of lentil and broccoli slurry? Mostly rich men | Gaby Hinsliff

Shortly after waking, Bryan Johnson drinks a murky concoction involving olive oil, cocoa flavanols and something derived from algae. Breakfast will be a blended green slurry of lentils, broccoli and mushrooms, with lunch and dinner not much different.

The 45-year-old American entrepreneur is religious about his sleep, follows a strict workout regime, monitors the performance of his vital organs using hospital-grade medical equipment, and suggests to his social – media followers that deviating from what he calls the “blueprint” to have a raucous night out getting wasted with friends is a form of self harm.

If your best friend suddenly started behaving like this, you’d worry she was developing an eating disorder. But men like Johnson – whose monastically disciplined routine went viral on Twitter this week – consider themselves biohackers: scientific pioneers pushing the boundaries of human life expectancy, in what amounts to an attempt to hack death itself. He claims his experiment – from which he hopes to devise rules anyone can use – allows him to resist ageing so successfully that “for every 365 days, I age 277 days”, whatever that means. Yet contemplating his dessert of olive oil with pellets of dark chocolate floating glumly in it, you have to ask if it’s worth it.

Who wants to live for ever? Not me, with all due respect to Freddie Mercury for asking, and possibly not you either. Only a third of Britons even want to make it to 100, according to a recent Ipsos poll carried out for the British not-for-profit initiative the Longevity Forum. This suggests less a death wish than a fear of what growing old may actually involve. Tellingly, the older the respondent already was, the less enthusiastic they were about getting very much older. Extreme age can look brutal, up close.

Personally, I want very much to live until my child no longer needs me, whenever that may be, and to enjoy some kind of retirement. But beyond that, I just want to live until it feels like enough, and then ideally to have some control over the end. I’d rather have a busy, happy, meaningful life and drop dead at 75 than make it to 150 and run out of ways to fill the endless days.

Perhaps at 74 I’ll feel differently, but intriguingly the poll found women less keen than men on a long life, although it couldn’t explain why. Are we perhaps less likely to see ageing as a competition, won by the last person standing? Do we worry more about outliving all our friends? But perhaps it’s just that men are statistically more likely to die sooner, so don’t take longevity for granted. For whatever reason, venture capitalists continue to pour billions into biotech companies promising to extend human lifespan, while Silicon Valley tech bros’ famed obsession with often scientifically questionable “human optimisation” regimes shows no sign of waning.

The former Twitter CEO, Jack Dorsey, an early biohacking devotee, swears by just one meal a day and a morning “salt juice” (a mix of water, lemon and Himalayan salt). Dave Asprey, CEO of the supplements company Bulletproof, describes in his book, Superhuman: The Bulletproof Plan to Age Backwards and Maybe Even Live Forever, his hopes of making it to 180. Some biohackers predict a future where we’ll voluntarily replace healthy limbs with prosthetics, engineering ourselves for optimal performance.

But beneath this exhausting quest for immortality, the constant tweaking of the bodily algorithm to ensure maximum efficiency, you sense anxiety and perhaps also the legacy of burnout. Johnson has tweeted about suffering from depression in the past, admitting that while building the tech company he eventually sold to PayPal for $800m – freeing him to pursue adventures in biohacking – he worked round the clock: “Days without sleeping was legend. Ragged state of being a badge of honour. Now I’m trying to make up for that.” Perhaps extreme health kicks like this are best understood as a reaction against an extreme way of life, replacing workaholism with a different form of driven behaviour.

Yet already the niche language of biohacking is filtering down, much like its less sciencey cousin “wellness”, to the rest of us mere mortals via glamorous Instagram influencers and magazine articles suggesting you can shave years off a suspiciously nebulously defined “biological age” by eating more berries, walking barefoot on grass or taking ice baths. Biohackers often say they’re interested in extending healthy life, not living just for living’s sake, and of course it’s good to want to stay fit for as long as possible, dodging Alzheimer’s or cancer or painfully crumbling bones if you can.

But there’s a difference between enthusiastically wanting to get the most from life and fearfully striving to reverse the cellular process of ageing via suspiciously rigid regimes. Much of that venture capital and restless energy might be more practically employed seeking not to defer old age indefinitely, but to take the terror out of it – through better treatments for horrible degenerative diseases, unsexy but useful technology that helps people stay independent at home for longer, and reliable social care.

The goal shouldn’t be to endlessly extend life but to create joy and purpose at every stage of it, whether that means easing pain at the very end or not making employees spend their 20s sleeping in the office. We don’t really need to hack death. What we need is to make life worth living.