From Woman's World · Hanna Wickes · · 1m 30s
Katy Perry says she's 33. Her body, anyway
Biological age tests are everywhere now, so here is what the science behind them can and cannot tell you.
In brief
Biological age tests are everywhere now, so here is what the science behind them can and cannot tell you. A biological age number is a snapshot of one slice of your biology, not a prediction of how long you will live. Originally reported by Woman's World.
From the lab to Instagram
Biological age tests used to live in research labs. Now they ship as at-home kits and show up in celebrity posts, with Katy Perry telling followers hers is 33.
Two different clocks
Chronological age counts calendar years. Biological age estimates how fast your body is aging next to peers born the same year, so a 60-year-old scoring 55 has a body resembling the average 55-year-old's.
“Biological age is real. There's a difference between your chronological age and your biology”
Reading tags on your DNA
Most aging clocks measure DNA methylation, where methyl groups attach to DNA over time and alter the cytosine base. More methylation at certain sites points to faster aging.
“You can use methylation to measure time in all cells that contain DNA”
What speeds the clock up
Steve Horvath spent over a decade at UCLA chasing this. Smoking, poor diet and inactivity all pushed the epigenetic clock forward in his research.
“pretty much any lifestyle factor that is bad for you”
Each test sees one slice
GrimAge reads blood methylation and flags cognitive decline risk. iAge tracks chronic inflammation, GlycanAge measures immune function, microbiome clocks estimate gut aging. You get a number, not a lifespan.
“At this point, if you want to do it, it must be based on curiosity”
The numbers wobble
Results shift within a single day. German soccer players tested right after a match looked far younger in a 2025 study, then returned to baseline hours later. Retest at the same time of day.
“Even if we optimize everything, it's [only] the rate of change which is modifiable”
The one thing
A biological age number is a snapshot of one slice of your biology, not a prediction of how long you will live.
