Tim Gurner – multimillionaire property developer, financial adviser to the poor and biohacker – famously blamed people’s penchant for smashed avocado for their inability to get on the housing ladder in a 2017 interview on 60 Minutes.

Fast forward to this week and Gurner, whose business portfolio boasts a $10bn pipeline of projects, had to apologise for suggesting workers were arrogant and needed to be reminded who was the boss.

At a summit hosted by the Australian Financial Review this week, he said unemployment should increase by up to 50% to put pressure on workers. “There’s been a systematic change where employees feel the employer is extremely lucky to have them as opposed to the other way around,” he said.

“We need to remind people that they work for the employer, not the other way around.”

He has since apologised, saying his comments were “deeply insensitive”.

Gurner’s willingness to offer free advice on how people should spend their money and time has drawn renewed attention on his own habits, and in particular some scattergun efforts to extend his healthy lifespan.

Gurner is one of a growing number of uber-rich guys who spend chunks of their fortune on biohacking, also known as garage biology. Some of the techniques he favours can be found at his longevity club, Saint Haven, in the Melbourne suburb of Collingwood.

The full package costs a cool $250,000, but the weekly entry price to the wellbeing nirvana costs around the amount of the average weekly household grocery bill – $150.

It’s not clear how much access to Saint Haven’s hyperbaric oxygen pods, cryotherapy or IV drips the starter price will get you, but you’ll have to wait anyway. Membership is sold out, although new sites are promised.

In May Gurner told the Financial Review (in an article his business website links to) he was a guinea pig for the $250,000 package with an annual full-body MRI, brain scans and monthly blood testing, which informs the composition of the 50 or 60 tablets he takes each day.

Biohacking is the new wave of the age-old desire to live forever, spearheaded by those with the money and the vainglorious focus to try the unproven, the untested and the unknown.

Last year, Forbes Australia shared Gurner’s “top 14 biohacks for ultimate performance and wellness”, promising the man would “share his full story” at their October summit.

He talks about owning his own small gym when he was younger, watching as his dad suffered cancer, and his wish for a longer and better life.

“Anything that is out there that’s a biohacking/testing thing, I’ve done it,” he said.

“From micro-dosing mushrooms to infrared saunas to steam to Oura [a smart ring], lymphatic drainage. Everything. I want to try everything and see what works for me.”

His top hacks list includes a bed cooling blanket, red light therapy, lymphatic drainage, a pulsed electromagnetic field mat and an anxiety blanket.

Guardian Australia has attempted to contact Gurner for comment.

‘You’re spending a lot for unproven interventions’

The gentler end of biohacking includes breathwork, meditation and dietary restrictions. But there are the fringe dwellers willing to try anything that someone links to longevity.

Notwithstanding Gurner’s claim that he wants to try “everything”, it is not suggested he has experimented with any illegal practices, or anything other than the specific techniques mentioned above. Other dudes (the high-profile ones are almost exclusively men) scoff dozens of supplements, take blood transfusions, get on IV drips and get in ice baths. They take experimental drugs and psychedelic micro-doses, and strictly restrict their caloric intake (without ever calling it a “diet”). They use drugs such as resveratrol and metformin “off script” and other chemicals that promise, but can’t prove, anti-ageing benefits.

“Grinders” embed chips or magnets under their skin to communicate directly with external technology, becoming cyborgs in the process. Others stitch together extreme diets, extreme lifestyle restrictions and extremely experimental lifestyles.

The tech entrepreneur Bryan Johnson stops eating at 11am, never goes out and has spent millions trying not to die. His “first date expectations” include “scheduled sex”, “u sleep alone” and “no sunny vacations”.

The former Twitter boss Jack Dorsey eats one meal a day, along with a morning “salt juice”.

The Facebook founder Mark Zuckerberg and Amazon’s Jeff Bezos have gone all buff bro, while Elon Musk has long argued that humans need to become cyborgs.

But many of these expensive biohacks are bunkum.

Prof Luigi Fontana from the University of Sydney, a longevity expert, says people are forking out cash while looking for a “magic pill”.

Fontana, the scientific director of the Charles Perkins Royal Prince Alfred clinic, says social media is full of people selling unproven longevity interventions. In most cases, he says, there is no scientific evidence they work.

Even famous scientists – credible sounding people – have been recruited to claim anti-ageing or metabolic effects from supplements, he says.

“Because these are not medications, so they don’t need to be prescribed, they are not under the regulation [of health authorities] – you can buy them at the supermarket as a supplement, you can do whatever you want,” Fontana says.

“So if you do a lot of marketing on socials, you have a lot of people who’ll buy them for a shortcut, an easy solution, [a] magic pill.”

For some things, such as hyperbaric chambers, there are clinical uses, such as to treat deep burns, he says. But that’s the limit.

“You’re spending a lot of money for unproven interventions – we don’t know if it’s good, bad or neutral.”

Diet, exercise, good sleep, less stress and cutting out alcohol and cigarettes are the only proven strategies to promote healthy longevity.

“Diet is the most powerful intervention to slow down the accumulation of damage,” Fontana says. “A healthy diet with high-quality food, low empty calories, primarily plant-based with lots of different vegetables, beans, fish, nuts, low fat-dairy.”

Intermittent fasting might help you lose weight, he says, but if the food you do eat is junk, you won’t get a good metabolic response.

Fontana says it’s important to do different types of exercise – including endurance, high interval, resistance and flexibility – along with stress reducers such as breathing techniques or mindfulness.

Smoking is bad, and drinking even a little bit each day is “not good”, he says, and definitely increases your cancer risk.

Fontana scoffs at biohacks, and says people are looking for easy solutions to complex problems.

“Based on the science we have, it’s a waste of money.”