When it comes to health, how important is our biological age?

Is 50 the new 30? Or is 80 the new 60? If you’re Bryan Johnson’s penis, 47 is the new 18.

The Californian tech millionaire’s quest to defy ageing has so far cost more than $US4 million and led him to swallow 111 pills every day, have dinner at 11am, practise his daily Kegels, undergo medical procedures including human growth hormone therapy, testosterone therapy, light therapy and blood transfusions, and sleep with “a tiny jetpack attached to his penis” to monitor his nighttime erections.

His return on investment has given him, he says, the bones of a 30-year-old, the heart of a 37-year-old and “the erection of an 18-year-old”, whatever that means.

Johnson’s obsession is emblematic of a broader interest in biological age: the heath metric du jour for those chasing the fountain of youth.

Turning back the biological clock? Bryan Johnson.Credit: Bloomberg Businessweek

“It’s a number that we all can relate to,” says nutritionist and exercise scientist Amelia Phillips, whose programs focus on healthy ageing. “And so if you are being told that you’re biologically younger or the opposite, it has quite a strong emotional response.”

We all know people who appear and act younger or older than their years. But, what does biological age really mean? How is it measured? To what extent can it be reversed? And what can it really tell us about the state of our bodies and our health?

What is biological age, and how is it measured?

While chronological age measures how long we’ve been alive, biological age refers to the accumulated damage to various cells that results from genetics, lifestyle, nutrition and the presence of diseases or medical conditions.

Its definition remains vague: “Biological age is a concept used loosely and with little objectivity to describe a shortfall between a population cohort average life expectancy and the perceived life expectancy of an individual of the same age.”

In other words, the idea is based on averages across certain populations at certain ages, not on accurately assessing individuals.

Also, there is no universal way of measuring it. There are different tests using different metrics – including inflammation, DNA methylation to assess epigenetic changes, online calculators or markers of BMI or cholesterol – to calculate our so-called biological age.

Depending on the test and how it is interpreted, you could be given an entirely different age each time. And only looking at one or two metrics gives a limited snapshot of our overall health, says molecular biologist Dr Tina Bianco-Miotto, of the University of Adelaide.

Biological age refers to the accumulated damage to various cells that results from genetics, lifestyle, nutrition and the presence of diseases or medical conditions.Credit: Marija Ercegovac

For instance, if you take a test that only measures markers of inflammation, which are associated with ageing, it doesn’t take into consideration your lifestyle, genetics, family history, environment or other factors that can also contribute to your health and ageing at a cellular level.

“What if you’ve decreased your inflammation but increased your oxidative stress?” asks Bianco-Miotto. “When you’re only testing one component, you get an unfair picture.”

And, says Phillips, the tests don’t differentiate between inflammation from an infection or chronic inflammation, which lingers for months or years and can cause collateral damage to organs and tissues throughout the body resulting in premature ageing and, potentially, a range of illness.

Another concern is the lack of transparency about how companies are making their calculations, says Dr Carissa Bonner, a behavioural scientist at the University of Sydney, who calls them “black box algorithms”.

Given “we’re nowhere near” personalised nutrition, Bianco-Miotto wonders how companies claim they can predict your biological age (and the best diet for your body) based on your DNA.

“If it’s a company looking to make money from follow-up services, they have an incentive for you to think you have a health problem,” Bonner says. “You also need to be careful about who owns the data you provide to these companies and where your personal health information might end up. Read the fine print.”

What can biological age tell us?

Professor Luigi Fontana, scientific director of the University of Sydney’s Charles Perkins Centre, says the various tests currently on the market are not accurate. However, he adds that in the next five or 10 years, they may be.

So, is there any benefit to getting your biological age tested? It depends.

“It’s that kind of snapshot in time, and it is a peek under the hood, but it is an important piece of a broader puzzle,” says Phillips. “It really becomes helpful if you are tracking over time where it’s like, ‘I’ve gone and made these couple of lifestyle tweaks, and I’ve retested, and I can see those markers have normalised.’”

Having feedback that reinforces positive lifestyle changes can be highly motivating, Phillips says.

“I guess it can create consistency and adherence to programs because they’re seeing that these small changes are actually making a difference.”

Bianco-Miotto agrees that if it motivates behaviour change, there is some value, though there is little evidence that these tests do that.

And although many decisions in our lives are dictated by chronological age, including fertility and when we have important health checks, the science is not yet there to personalise these based on biological age.

“Although some people may want to be younger, there is no changing how old we actually are,” Bonner says. “The short answer is your chronological age is probably a more reliable indicator of health risks than current measures of biological age.”

She adds that there is interesting research emerging in biological ageing, by measuring telomere length, for instance, but the technology is not quite there yet.

“You don’t really need an expensive test to tell you whether your lifestyle is healthy or not, and tests to assess your risk of specific diseases based on blood markers should be guided by a health professional,” Bonner says. “So the best place to start is your GP.”

‘Although some people may want to be younger, there is no changing how old we actually are.’

Dr Carissa Bonner, behavioural scientist

Can we slow, or reverse, our biological age?

Fontana says there is no doubt we can slow down biological ageing.

But it’s by doing things much less exciting than jetpacks, transfusions or experimental therapies – it’s by exercising regularly (a mix of training strength, speed, stability and aerobic efficiency), quitting smoking, focusing on cultivating and maintaining quality relationships, drinking less, prioritising sleep, having sex, managing stress and exposure to the sun, as well as eating a little less and consuming a Mediterranean-style diet of mostly plants, good fats and minimally processed foods.

By changing our behaviour, we can alter the activity of our genes.

For instance, people who smoke have lower DNA methylation levels (where a chemical group is added to the DNA, changing the gene’s behaviour) in certain genes than non-smokers. By quitting smoking, the changes ultimately reverse.

Biological ageing can be slowed down, mainly by committing to healthy habits.Credit: iStock

Longevity researchers are working on reversing age at a biological level, by tinkering with gene expression, but it remains fraught with issues. Some experts believe that if and when they fine-tune the approach it will more likely be used to treat certain health problems, rather than turning back time in our whole body.

As for Bryan Johnston, Bianco-Miotto reminds that genetics is at play as much as his behaviours: “If 100 people did exactly what he did, we wouldn’t all get the same answers.”

A good life is as important as the youthful life, she adds. “If you want to spend all day, every day focused on that aspect of ageing and restricting what you eat and exercising, you probably would be considered younger, but it wouldn’t be sustainable for the majority of us.”

And, there is no scientific evidence so far that we can reverse biological age, Fontana says: “It’s a marketing strategy.”

Johnson, he suggests, has an ego as sizeable as his bank account, and his outlandish and highly publicised pursuit has been a “very well-crafted strategy to sell something”.

Indeed, this year Johnson announced he was launching “the most nutritious program in history”. For US$121 ($182) you can buy a pack of Blueprint “Super Veggie ready-to-mix spread”, which contains carrots, broccoli, cauliflower and some mixed mushrooms and cocoa powder. Or for US$92 you can buy a couple of bottles of extra virgin olive oil.

It might not reverse your age, but it could well set your savings back several years.

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