Epigenetic clocks: how old is your body really?

You have two ages. One is on your driver’s licence. The other is written in your DNA. And they are probably not the same.

What I’m talking about is biological age. The way your cells are actually ageing, measured through something called epigenetic clocks. There’s a new class of tests that look at DNA methylation patterns and tell you how fast you’re ageing at the cellular level. They’re turning out to predict disease and longevity better than simply knowing how old you are.

The interesting part: the things that slow your biological age aren’t secrets. They’re the same basics everyone talks about but most people don’t actually do.

How the clocks work

Your DNA sequence is fixed from birth. But DNA doesn’t just sit there like a static blueprint. Chemical tags called methylation marks are constantly being added to and removed from specific sites on the genome in response to how you live. What you eat. How much you move. How well you sleep. Whether you’re chronically stressed.

Think of methylation as sticky notes on your genes, turning them up or down based on your body’s experience. Crucially, the marks are reversible. You can change them.

By looking at specific patterns of methylation across hundreds of sites, scientists can estimate how old someone’s cells actually are. That estimate doesn’t always match chronological age. Some people have cells that look younger than their years. Others look significantly older. The difference correlates with health outcomes and with how long people actually live.

What the 2025 comparison of 14 clocks shows

A major 2025 study published in Nature Communications compared 14 different epigenetic clocks against 174 disease outcomes across 18,859 individuals.¹ The best-performing clocks predicted 10-year onset of specific diseases (cardiovascular disease, type 2 diabetes, chronic kidney disease, cognitive decline) and overall mortality above and beyond chronological age alone.

This is meaningful for research. Your established clinical risk factors , blood pressure, cholesterol, smoking history, fitness level. Still drive treatment decisions at the individual level. But as population-level predictors, the second-generation clocks (GrimAge, PhenoAge, and particularly DunedinPACE) outperform chronological age.

DunedinPACE: the pace-of-ageing clock

One clock in particular stands out. DunedinPACE was developed from the Dunedin longitudinal study in New Zealand, which has tracked a cohort of over a thousand people from birth into their forties.²

Unlike most clocks, which estimate biological age at a single time point, DunedinPACE measures the pace of ageing. How fast are your cells ageing right now, relative to your chronological age?

• Score of 1.0 = ageing at chronological pace.
• Score of 1.2 = ageing 20% faster than chronological time.
• Score of 0.8 = ageing 20% slower.

Two people at the same chronological age can have very different pace scores. A 60-year-old with a score of 1.2 has cells ageing like someone in their early 70s. The same 60-year-old with a score of 0.8 is ageing more like someone in their late 40s.

That spread, at identical chronological ages, is part of why some 70-year-olds run half marathons and others struggle with stairs. Biology isn’t destiny. But it is keeping score.

What accelerates epigenetic ageing

This is the part where the research becomes useful, because the answers aren’t surprising.

• Smoking. Accelerates methylation ageing in respiratory tissues and overall pace substantially. The effect is dose-dependent and begins to reverse after quitting.
• High BMI. Chronically elevated body fat drives low-grade inflammation that leaves a methylation signature of accelerated ageing.
• Elevated blood glucose. Insulin resistance and diabetes show up in the methylation data as accelerated ageing.
• Uncontrolled hypertension.
• Chronic inflammation. The common pathway many of the above converge on.

The same general risk factors that drive cardiovascular disease, dementia, and metabolic disease also accelerate epigenetic ageing. That’s not a coincidence. It’s the mechanism.

What slows it

Equally unsurprising:

• Regular exercise, particularly a combination of resistance training and cardiorespiratory work.
• Good sleep, both duration and consistency.
• Stable blood sugar from a diet of mostly minimally processed foods.
• Managed chronic stress. Not eliminated. Just managed.
• Strong relationships and social connection.
• Adequate nutrition with sufficient protein, especially with age.

None of this is new. What the epigenetic research adds is a mechanism: the basics show up at the cellular level. Methylation patterns shift in response to behaviour within weeks to months. The clock isn’t broken. It’s responsive.³

Should you get an epigenetic age test?

The commercial market for epigenetic testing is growing. Here’s my honest position as a clinician: the science is real, the clocks are predictive, but they are still primarily research tools. We’re not yet at the point where a single test result should guide your treatment decisions.

If you got a test saying your biological age was five years higher than your chronological age, what would you actually do differently? Quit smoking if you smoke. Exercise more. Sleep better. Manage weight and blood pressure.

The honest answer is: exactly what you should be doing anyway. Your clinical markers already tell you most of what an epigenetic test would. The test doesn’t change the advice.

That said, the tests might be genuinely motivating for some people. Seeing that your lifestyle changes are moving your biological age down can be powerful feedback. If you find that motivating, go ahead. Just know it’s not required information.

A note on supplements marketed as “anti-ageing”

There is growing interest in supplements claiming to optimise epigenetic ageing. Methylation donors. NAD precursors. Sirtuin activators. Some of these compounds are genuinely interesting in early research, particularly the NAD metabolism work.

But the honest position right now is that the evidence for their effect on human epigenetic ageing is still developing, and none of them come close to the effect size you get from consistent exercise, quality sleep, and not smoking.

By all means watch the research. But the fundamentals still outperform the supplements at this stage, and likely will for a long time.

The bottom line

Your cells are ageing. That’s biology. The rate at which they age is something you have genuine control over.

If you’re sleeping well, moving regularly, managing stress, eating real food, and maintaining stable weight and blood pressure, your biological age is probably lower than your chronological age. The epigenetic research simply gives us a mechanism to explain why the basics work.

Pick one thing. Sleep consistency, or movement, or nutrition. Start there. Your cells are paying attention.