It’s 5pm in the Farrant household and Jack, six, and Thomas, four, are currently manifesting their desires in the form of Lego. To an outsider this looks like two small children playing with toys, but their mother Catherine proudly points out that Jack has built a yacht – something he is helping his family to acquire via visualisation exercises.

‘Dinner’s ready,’ calls out the nanny. In line with the family’s Paleo diet – of anti-inflammatory, natural foods – they have octopus cooked with lemongrass, and fish-bone broth. ‘Yes, my favourite,’ cries Jack happily, while his mum explains exactly what the broth is: ‘It’s an age-old elixir that’s made from boiling wild bones. It’s very high in iodine, which most of us are deficient in.’

After dinner, the children can continue to express their creativity, or watch some television – though if they’re going to do the latter after 6pm they need to put on their ‘blue-light blockers’, glasses with amber lenses to block the blue light of technology from affecting their sleep. ‘We also do red-light therapy,’ explains Catherine, pointing to a red dinosaur lamp in the boys’ bedroom. ‘It’s to help the body’s natural rhythms of sunset with exposure to red colours at night, and blue and white light in the morning.’

But before Jack and Thomas begin their red-light therapy, it’s time for their twice-weekly bentonite-clay and Epsom-salt bath. ‘I don’t want to,’ whines Thomas. But Catherine is firm, and soon they’re playing happily in the family tub. It looks like a normal bath time, just a lot messier. The idea is that the clay will help remove the toxins the family are exposed to living in the capital and boost their immune systems.

The Farrants are just one of a growing number of families who are ‘biohacking’, or ‘hacking their biology’ at home using DIY methods, with the goal of living healthier lives and therefore longer ones. As an industry, biohacking is expected to have a global compound annual growth rate of 19.42 per cent between 2017 and 2023, to reach a predicted value of £19.7 billion.

Biohacking originated in America, the term popularised by Dave Asprey, a Silicon Valley tech entrepreneur who spent two decades and more than $1 million to hack his own biology, losing 100lb and claiming to have lifted his IQ by 20 points. But it has grown on this side of the Atlantic, too – in the UK, the Health Optimisation Summit has over 1,000 members. Founder Tim Gray explains: ‘Americans are generally more products- and supplements-focused with biohacking. The Scandinavians are more tech-based and into extreme nature like foraging. Here in the UK, we’re more diverse and take the best techniques from all over the world.’

Gray believes biohacking has ‘exploded in the last couple of years’ due to the growing awareness around health and high levels of stress and obesity. ‘The more we connect on social media, the more apparent it is that we’re not getting healthier and there’s a huge amount of people talking about bloating issues or intolerances or chronic fatigue. They’re searching for results and not finding them – so they turn to biohacking.’

Dr Jack Stilgoe, associate professor of science and technology studies at University College London and author of Who’s Driving Innovation?, explains that biohacking ‘often stands apart from orthodox science, which means that it can either be radical, cutting edge, self-experimentation – the sort of thing that a doctor would not be allowed to do on a patient – or it could be more like alternative therapies, where people are trying things that may have slender evidence because little else has worked for them.’

Examples of famous biohackers range from the extreme Elon Musk, who has argued that humans need to become cyborgs to survive an inevitable robot uprising, to Twitter co-founder Jack Dorsey, who practises intermittent fasting and regularly takes saunas and ice baths.

‘It’s anything that optimises your health,’ says Tim Gray. ‘It’s not just being stuck in a current system that isn’t working. There might not be studies yet for all this, but biohackers take things into their own hands and test the results on themselves. There’s the longevity crowd, who are tech billionaires and don’t want to die – that’s where everyone’s investing. But in my mind, if you optimise your health, get decent sleep, eat what your body needs, and are less stressed, you’ll live for longer, which is longevity in itself. We’re all doing it for the same reasons.’

In the Farrant household, biohacking (specifically the bone broth, which helped improve gut health) is credited with curing Thomas’s severe eczema in a way that medicine prescribed by a doctor didn’t. It also dramatically increased the energy and general health levels of Catherine, 36 – who quit her job as a partner at a wealth-management firm in 2018 to work full-time on her company Ossa Organic, which makes bone broth among other products – and her husband Michael, 40, director of a reputation- and crisis-management company. ‘He’s got really into all this, which is great,’ says Catherine, who began biohacking and researching ways to improve her health before having her first child, then shared the methods with her husband and now their sons. ‘We both feel so much better than when we were in our 20s, eating takeaways and having no idea about what we were doing to our bodies.’

As well as their no-sugar, no-processed-food Paleo diet, which they follow to boost their gut health, the family have installed a water-filter system into their home at a cost of £300 per year, painted their walls with a non-toxic paint designed to purify the air, and ditched spring-coil mattresses to reduce exposure to electromagnetic fields. ‘People say it’s expensive, but we changed our mattresses over the space of several years,’ she explains. ‘The paint was about 10 per cent more expensive than Farrow & Ball, and we get things like fluoride-free toothpaste and paraben-free shampoo at TK Maxx for under £5. And organic food is expensive, but it’s cheaper than living off steroid creams, which was what doctors said our son needed for his eczema.’

On top of that, their cleaning products are natural and free from toxic chemicals, they’ve switched laundry softener for white-wine vinegar, they have ‘electromagnetic-field blockers’ on their mobile phones, and Catherine makes their sun creams and body lotions using coconut oil and tallow (a rendered form of beef fat). It’s all to help remove the ‘toxic load’ from the body, and ‘make the body faster and nimbler at fighting potential viruses, bugs and colds’.

There isn’t necessarily scientific evidence to support every biohack, but for Catherine, the proof is in the family’s glowing skin, bright hair, and the fact they’re rarely ill. ‘I think doctors have their place in trauma, which could be major surgery,’ she says. ‘But we’d avoid things like paracetamol or Calpol. For us, homeopathy has worked really well.’

Dr Stilgoe explains that while homeopathy often has no scientific evidence to back up its claimed benefits, beyond being a placebo, it is at least generally safe (as long as it supplements rather than replaces other medical treatments where needed). ‘The worry would be not just if people are taking things that are untested or known to be dangerous, but if people have treatable illnesses and are forgoing things that we know work.’

In north London, Tony Riddle, 44, and his wife Katarina, 39, also practise biohacking with their four children, Lola, 10, Millie, eight, Tallulah, three, and Bow, four months. The biggest change they’ve made is ‘ground living’. They have no chairs, sofas or beds in their home; instead, they sit on cushions, crouch on the floor or stand. They do have a dining table – but Tony cut the legs off, so now they can all sit around it on the floor.

‘It can be perceived as socially extreme, but for me we’re just aligning with a more biologically natural way of living,’ says Tony, an ultra-athlete and natural-lifestyle coach. ‘I feel like we’re not so much biohacking as just hacking a social norm.’

He believes that ground living, and going back to a more primal path, is the best way to erase problems with posture that come from our sedentary lives. ‘We spent 90 per cent of our time indoors, where we’re mostly sedentary, which creates an unnatural posture. Ground living helps undo that.’

His children happily sit down to eat their lunch (black-bean burgers and sweet-potato fries with salad) at the low table, without slouching or fidgeting. They haven’t used high chairs or pushchairs at all – Katarina carries Bow in a sling – and all have impeccable posture. ‘They’re born innately wild and natural, so it’s more about, how can you preserve that?’ explains Tony, as Millie hangs from and does chin-ups on a bar he’s installed in the kitchen doorway. For her it’s just fun, but she’s actually practising ‘brachiation’ – arm-swinging and hanging, common in the primate world and important for upper-body strength and mobility but, again, neglected by modern humans.

Tony’s ultimate goal is to upgrade his family’s existing environment to make it work for their health and happiness, rather than against it: ‘This is not just about living longer, although longevity is certainly a benefit, but it’s about designing simple ways of living that create greater health and wellbeing for future generations and our planet,’ he says. He also quotes a study that found children with higher levels of aerobic fitness performed better in learning and memory tasks than more sedentary children.

As part of their ‘rewilding’, as Tony refers to their efforts, the family also practise barefoot living. Tony regularly runs marathons barefoot – he ran 874 miles, the length of the UK, without shoes in 30 days back in September. When the family do use shoes, they prefer to wear Vivobarefoot, a brand that mimics the natural feel of being without them. ‘You lack the grounding, sensorial aspect of being barefoot with them,’ explains Tony. ‘But you get the anatomical benefits, as the shape allows the top of the foot to spread out, and minimises risk of injury as the arch and ankle can absorb most of the shock of hitting the ground, as they’re meant to, rather than the knees and hips, which is what so often happens.’

They now homeschool their children for many reasons, one of which is to ensure they don’t have to spend all day in an environment with chairs and tables that will undo the benefits that ground living affords them at home. ‘If there was an alternative school, maybe we would have considered that,’ says Katarina. ‘But I believe children can educate themselves. As a parent and teacher you provide the stimulating environment, but they lead the education.’

Tony and Katarina do allow exceptions – the children go to friends’ houses and restaurants where they don’t practise ground living, and the Riddles have a set of garden furniture they bring inside for when elderly relatives come over. ‘We don’t want to isolate the kids,’ says Tony. ‘We get public transport too, but normally on the Tube, they’ll be squatting or hanging from the bars, or Tube surfing [using core strength to balance while standing on the train, instead of holding on].’

Both sets of grandparents – Tony’s parents in England and Katarina’s in Slovakia – have struggled with some of the couple’s decisions on how to raise their children, from not using pushchairs to homeschooling and not giving them any processed foods. ‘It’s been very challenging for them,’ admits Katarina. ‘We’ve had situations where my parents gave them sugar, which they’re not used to, and I had to go through it all with them. But now they’ve seen the results, they get it, and they’re actually starting to make changes to their own diets too.’

While Tony recognises that their choices can be seen as eccentric by some, he points out that ground living is less unusual in countries like Japan, and in their social circle, where many other parents homeschool.

‘I was recently with the kids in a playground when a lady came over and said, “Your children seem so different and cool,”’ laughs Katarina. ‘I think that [the way we’re raising them] does help them be more self-confident and calm.’

‘And stronger,’ adds Tony. ‘Things like monkey bars are really easy for them.’

It also means the children are less tech-obsessed than many – the Riddles don’t own a TV (though they have movies days twice a week, when they watch films on the family Mac). Tony wears amber glasses for computer work at night, but ‘to avoid always looking like Bono’, they’ve also swapped their ordinary lightbulbs for colour-changing bulbs (the colour of the light can be altered from white to amber to red depending on the time of day). ‘That artificial, blue light we’re feeding our bodies with each and every night shuts off the release of melatonin,’ he says, going on to explain that an absence or reduction of melatonin in the body has been linked to weight gain, type 2 diabetes, cancer and depression. ‘Melatonin is triggered for release by biological darkness, which we would have experienced as hunter-gatherers – darkness that would have included firelight, moon and starlight.’

By replacing their lightbulbs, and making sure the children are asleep by 8pm and awake with the sunrise, the family are in sync with their circadian rhythms (the body’s natural, internal system that regulates feelings of sleepiness and wakefulness over a 24-hour period).

Dr Alex Zhavoronkov, author of The Ageless Generation: How Advances in Biomedicine Will Transform the Global Economy and CEO of Insilico Medicine, believes that biohacks like these may be helpful, but doubts their ability to drastically improve health. ‘Today there are very few new ideas in biohacking that go beyond “what your mother told you”,’ he says. ‘The biohacks described may yield only marginal benefits. I think that intermittent fasting and regular sleep are likely to improve performance and marginally increase longevity. But I do not recommend any of these interventions. At this point there is very little clinical proof that any of [them] may work.’

He believes that society is currently split into two extremes. ‘There’s the highly health- and performance-conscious and the very health-ignorant. The first group is pushing themselves to the new limits and the other is driving the obesity epidemic.’ He steers clear of the term ‘biohacking’ but believes that people can improve their health by educating themselves so they can make decisions based on hard science. ‘Most of the people engaged in biohacking do not have advanced medical or scientific degrees.’

While both the Riddles and the Farrants seem to be enjoying the benefits of their biohacking, medical experts stress that people should consult specialists and doctors before dramatically changing their diets and lifestyles. But Catherine says that anyone interested in biohacking doesn’t need to overhaul their entire life. ‘It’s about just finding maybe one or two things you want to do, and starting from there,’ she tells me. ‘Whether it’s deciding to change your shampoo and beauty products for chemical-free ones, or changing your diet, it’s whatever’s right for you.

‘My advice is just to try it for yourself and see the results,’ she goes on. ‘We don’t say that anyone should be like us or live like we do. We just let people see what we’re doing, and then ask questions, and maybe then they’ll start doing similar things, like getting a pair of blue-light blockers, which are really cheap, to improve their sleep.’

But the most positive view on biohacking comes from the children themselves. Thomas and Jack happily slurp up their bone broth, throw clay at each other in the bath, and ooze confidence. Meanwhile, Lola and Millie love being homeschooled so much that they ask for extra exams, can swing like apes from bars, and have no issue with sitting and lying on the ground for hours on end. The jury’s still out on how they’ll feel about their unusual lifestyles when they hit adolescence, but for now, they’re a glowing advertisement for their parents’ biohacks.