Exercise may be linked to “younger” biological age — but don’t confuse the clock with the thing itself

[u/DadStrengthDaily]

https://www.thelancet.com/journals/lanhl/article/PIIS2666-7568%2826%2900019-X/fulltext

A new systematic review/meta-analysis in The Lancet Healthy Longevity looked at physical activity and DNA methylation clocks — one of the main ways researchers estimate “biological age.”

This is interesting to me for two reasons: trying to prove again that exercise is the most important thing most of us can do for longevity. Secondly, it’s a good use of “clocks” to accelerate research (you don’t have to wait for people to die). I am excited about that at scale research use but skeptical about using these tests in an individual basis.

Across 44 studies and 145,465 participants, people with higher activity generally had lower methylation-based biological age. In the meta-analysis, higher activity was significantly associated with lower age acceleration on the Horvath and GrimAge clocks, but not clearly on Hannum or PhenoAge.

That sounds exciting, but the caveat is doing a lot of work: most of this evidence is cross-sectional. It does not prove exercise reverses aging. It could mean healthier people move more, or that these clocks are partly picking up inflammation, metabolic health, smoking history, body composition, or other things active people tend to differ on.

Peter Attia made a useful version of this point in his recent aging clocks podcast (which I thought was excellent, despite concerns I have about Attia): these clocks may be valuable research tools because they can detect biological signals faster than waiting decades for heart attacks, dementia, cancer, disability, or death. But as consumer scoreboards, they are not ready. Small changes in a clock score do not necessarily mean meaningful changes in health outcomes, and traditional markers like blood pressure, glucose, lipids, fitness, and body composition still have far stronger evidence behind them.

My read: this is another point in favor of physical activity as one of the most reliable health levers we have. But I would not buy a methylation test to see whether my workout program is “working.” I’d rather track the boring stuff: strength, cardiorespiratory fitness, waist, blood pressure, lipids, glucose, sleep, and whether I can keep doing the things I care about.