If exercise supports healthy aging, you might expect its effects to appear on a biological age test.
Research suggests that they sometimes do.
But there is an important complication: different epigenetic clocks do not always give the same answer.
That is exactly what researchers found when they examined physical activity and biological age across dozens of studies.
What is epigenetic age?
As we grow older, patterns of chemical modifications called DNA methylation change throughout our genome.
Scientists can analyse selected patterns and use mathematical models known as epigenetic clocks to estimate aspects of biological aging.
If an epigenetic measure indicates more advanced aging than expected for someone’s chronological age, this is often described as epigenetic age acceleration.
If it indicates less advanced aging, the profile may be considered more favourable.
But there is not just one epigenetic clock.
Researchers have developed different clocks using different sets of biological information and for different purposes.
What happens when physical activity is compared with these clocks?
A large 2026 systematic review examined 44 studies involving more than 145,000 participants.
Across the studies, higher physical activity was generally associated with lower DNA methylation age, although many individual results were not statistically significant.
When researchers combined comparable data in a meta-analysis, an interesting pattern appeared.
Higher physical activity was significantly associated with lower age acceleration measured by:
* Horvath * GrimAge
But there was no statistically significant association for:
* Hannum * PhenoAge
So which result is correct?
Potentially, all of them.
Different clocks measure different aspects of aging
The term “biological age” can make it sound as though there is one hidden age inside your body waiting to be measured.
Biology is more complicated.
Epigenetic clocks are built using different DNA methylation patterns and statistical methods. Some were developed primarily to estimate chronological age, while newer approaches incorporate biological signals related to health outcomes and mortality.
This means two clocks can respond differently to the same lifestyle factor.
A change detected by one clock therefore should not automatically be expected to appear on every other biological age measure.
Why was GrimAge particularly interesting?
The association between physical activity and epigenetic age acceleration was stronger for GrimAge than for the Horvath measure in this analysis.
That is interesting because GrimAge was developed to capture biological information associated with mortality and age-related health risks.
The finding is consistent with the broader evidence that physical activity is strongly connected with long-term health.
But it does not prove that exercise directly changes GrimAge or slows the underlying aging process.
The studies included in the combined analysis were cross-sectional, so they cannot establish cause and effect.
What does this mean if you take a biological age test?
A biological age result should be interpreted in context.
If you become more physically active but one particular biological age score does not improve, this does not mean that exercise is failing to benefit your health.
Equally, an improvement in one epigenetic clock should not automatically be interpreted as proof that your entire body is aging more slowly.
Biological age biomarkers can provide useful information, but they represent particular aspects of a much more complex aging process.
For healthy aging, established clinical measures — including cardiovascular risk, metabolic health, physical fitness, muscle strength and functional capacity — remain important alongside emerging biological age technologies.
Based on Research
Shan J, Tay JH, Wang W, et al. Physical activity and biological age measured by DNA methylation clocks: a systematic review and meta-analysis. The Lancet Healthy Longevity. 2026.
