For how we live.
Epigenetic clocks estimate a 'biological age' from DNA methylation. A 2022 study found technical noise alone could shift the result by up to 9 years between replicates of the same sample.
The only long randomised trial of calorie restriction in non-obese adults improved cardiometabolic risk and modestly slowed one measure of biological ageing. Participants never hit the 25% target.
Consumer clocks report an age, an age gap or a pace of ageing. Expert panels agree no single biomarker is sufficient — and clocks have failed to move when an intervention demonstrably worked.
In 276 adults tested at 60, the differences in GrimAge and DunedinPACE were small, their intervals crossed zero, and most of what was there disappeared once smoking was accounted for.
Longevity trials want a measurement that moves in months instead of decades. A Berlin study ranked the candidates, and a four-week diet trial showed what a clock does when nothing much happens.