Expert Answer
Are biological age tests accurate?
Quick Answer
Not as a prediction of how long you will live. Steve Horvath, who built the GrimAge clock, told Rhonda Patrick that a GrimAge 10 years below your calendar age does not mean 10 extra years of life. Attia agrees. Hyman and Johnson still track the tests as a personal trend line, which is the narrower job the panel supports.
What Researchers Say
Her channel has carried both sides. She hosted Steve Horvath, who developed the epigenetic clocks, and in 2026 hosted immunologist Derya Unutmaz, who argues the clocks are run on a blood draw and therefore read the cell populations in that sample rather than the whole organism. His alternative is functional: VO2 max, muscle strength, and walking capacity.
“these are all phenotypic like you don't even have to probably withdraw a blood just measuring the ability of uh of an elderly person uh can they walk uh better you know 100 meters than they used to”
Dr. Derya Unutmaz, on Rhonda Patrick's show, on the record @ 124:38
Rejects the idea that any single blood-based marker predicts remaining years of life, and argues physical performance separates people far better. His position is that a flattering test result is not evidence of a longer life.
“if you get a biological test at the age of 50 that says you are 25 before you give yourself high fives ask yourself the following question does that really mean that you're going to live another 55 years”
Peter Attia, on the record @ 2:58
Runs the tests on himself and reports his own results on air, while openly asking whether the clocks are reliable enough to trust his own improvement. He treats them as one input among DEXA, inflammation panels and standard labs.
“I went back even though I got two years older now I'm 64 on the same test I went to from 43 when I was 62 to 39 When I'm 64”
Mark Hyman, on the record @ 11:45
The Blueprint program is built on tracked biological age and pace of aging as the primary outcome measure. Note the on-air claim is made by a team member describing Johnson's results, not by Johnson himself.
“actual biological age um is probably that's probably our best best metric right now and we're continuing to slow the speed of aging um so down to like less than what uh 0.5”
A Blueprint team member, on Bryan Johnson's show, on the record @ 30:29
Has hosted guests on both sides, including David Sinclair on accessible biological age testing and Michael Snyder on the clocks' lack of actionable detail, without stating a position of his own in the analyzed videos.
Detailed Answer
The honest answer depends on what you are asking the test to do. As a prediction of your lifespan, the people who built these clocks say plainly that it does not work. As a repeated measurement of your own trend over years, two of the five experts use them that way and defend it.
The strongest statement comes from the person with the least incentive to make it. Steve Horvath developed the epigenetic clocks, and on Rhonda Patrick's show he asked listeners not to read a result as a life expectancy: "please do not translate that age estimate in your mind into an estimate when you will die… if your grim age is 10 years younger than your calendar age, it does not mean you will now live 10 years longer than the average person" (50:34). What GrimAge actually measures, he explains, is the instantaneous risk of dying in the next year relative to people of the same age and sex.
Attia lands in the same place from a different direction. His framing is that no single blood-based marker predicts remaining years well, and that a test telling a 50-year-old they are 25 is not a promise of another 55 years. He points people back to physical performance — VO2 max, strength, balance — because those show large, measurable gradations between people of the same age.
In 2026 an immunologist added a mechanical objection. Derya Unutmaz, who researches aging, told Patrick that the clocks are typically run on a blood draw, so what they read is the methylation state of the cell populations in that tube. Your immune cell mix shifts with infection, stress, training and sleep, and the number moves with it. His alternative is functional and cheap: whether an older person can walk 100 meters better than they used to.
The other side is real and worth stating fairly. Hyman tracks his own methylation age and has reported it moving from 43 to 39 across two chronological years, and Johnson's Blueprint program treats tracked biological age and pace of aging as its primary outcome. Both are using the test as a trend line on one person over time, which is a much narrower claim than "this is your biological age."
That distinction is where the panel actually converges. Comparing your number to a friend's, or reading it as years of life banked, is the use the evidence does not support — and the use most consumer marketing implies. Watching your own number move, alongside markers that are free to measure, is the use nobody in this set argues against. This page is educational synthesis of what these experts said on video, not medical advice.
Related Questions
Can a biological age test tell you how long you will live?
No. Steve Horvath, who developed the GrimAge clock, specifically asks people not to read a result that way — a GrimAge 10 years below your calendar age does not mean 10 extra years of life. He describes GrimAge as a measure of your risk of dying in the next year compared with people of the same age and sex.
Why do two biological age tests give different results?
Different clocks track different markers — inflammation, metabolic health, mortality risk — so they are not measuring one shared quantity. Derya Unutmaz adds that a blood-based clock reads the cell populations in that sample, and your immune cell mix shifts with infection, stress, training and sleep.
What do the experts measure instead?
Physical performance. Attia points to VO2 max, strength and balance because they separate people of the same age dramatically. Unutmaz uses the same category, down to whether an older person can walk 100 meters better than before. These are free to measure and repeatable at home.
Is there any use for an epigenetic age test?
As a trend line on yourself, tracked over years, yes — that is how Hyman and Johnson use them. Hyman has reported his own methylation age moving from 43 to 39 while he aged two years chronologically. The weak use is comparing your number to someone else's or reading it as banked lifespan.
Do all five experts agree about biological age tests?
No, this is one of the more contested topics in the set. Attia rejects them as lifespan predictors, Patrick has aired both the clocks' inventor and a critic, Hyman and Johnson use them as personal trend lines, and Huberman has not stated a position of his own in the analyzed videos.
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