How Old Are You, Really?

Right now everyone wants to know their biological age. The wearables sell it, the clinics sell it, the supplement companies sell it. People walk in genuinely rattled that an app told them their "true age" is seven years north of their driver's license.

I understand the appeal. It's a more interesting question than how many times you've circled the sun.

But you don't have one age. You have at least four — chronological, biological, functional, and emotional — and the inconvenient truth is that they rarely line up. I've met very old people who never grew into adults. I've met very young people who grew up far too early.

Premature growth comes at a cost. When life advances you a few stages before you've collected the tools, it's stressful. You're operating heavy machinery without the manual. It's hard being a child whose parents depend on them, and most of us bump into a milder version of this the day we have kids of our own. We still feel like children, handed the job of raising adults.

Here's the part nobody markets to you. The age everyone is chasing — the biological one on your wrist — is the least useful of the four. The two that actually shape your life are the two nobody sells you a subscription for.

Chronological Age

There isn't much to say here. You count the years from the day you were born to today. Done.

It's the only one of the four you can't argue with, and the only one that's honestly measurable. Everything after this gets fuzzier.

Biological Age

The moment you start talking about biological age, you've quietly left the world of things that can actually be measured. What you're really buying is a proposed assumption about how efficiently your cells are running.

Most of the epigenetic clocks look at your methylation state. Methylation is the act of tacking on a methyl group — a single carbon unit — to your genetic material. The underlying question these tools are reaching for is your personalized rate of aging, not just the static number. Then there are the omics, which are having a moment: the transcriptomic (gene expression), the proteomic (plasma protein levels), the metabolomic (circulating metabolites), and the glycomic (based on glycosylation, which adds a sugar group to a molecule).

Strip away the branding and the theme across all of them is the same: inflammation, metabolic regulation, and tissue-level damage. Damage shows up in the repair signatures.

The short answer is that none of these are useful clinically. Not yet, and not for you specifically. I see patients tie their entire sense of health to whatever number their device coughs up that week, which is a strange thing to outsource to a wristband. One of the quieter problems is repeatability. A test that's scientifically worth anything should give you roughly the same answer twice. Specialized tests — age tests very much included — often don't.

I want to be careful not to throw the baby out with the bathwater. The markers feeding these clocks are real, and managing them matters. Inflammation, blood sugar, and metabolic health are worth your attention. It's the composite score I'd hold loosely. Think of the biological age number as a stock ticker you've started checking ten times a day — entertaining, volatile, and almost entirely disconnected from whether the underlying business is sound.

Functional Age

This one I actually like.

The U.S. Army runs a test now called the AFT, with defined performance standards across a battery of physical events, broken out by age and sex. You can borrow the logic to build yourself a functional age: find the youngest age bracket whose standards you can still hang with. If you're forty and performing like the twenty-five-year-old column, that tells you something a methylation panel can't. I'd argue the comparison is even more honest if you benchmark against an active population rather than the general one, since the general baseline has quietly gotten very low.

I think these functional tests are a far better gauge of where someone really stands. We tend to overemphasize whatever we already enjoy. Most people are either lifters or runners, and they'll defend their camp to the death. The answer is that you need both. You need enough strength to keep your quality of life as you age, and you need cardiovascular fitness to keep the vascular system — and everything downstream of it — in working order. Pick one and you've optimized half a person.

Emotional Age

Call it emotional age or psychological maturity; they're the same idea, and it's the one we neglect most.

There's an old archetypal progression people use — child, warrior, king or queen, and finally the wise elder. What you notice in real life is that nobody marches cleanly up that ladder. People progress and regress, sometimes within the same afternoon. When someone gets emotionally hijacked, their maturity drops a stage or two and they start making impulsive calls instead of asking what the best decision is on the odds. Emotion is the enemy of probabilistic thinking, and probabilistic thinking is most of the game.

Emotional age tracks closely with someone's knowledge base, which is good news, because knowledge is something you can build. Travel, books, hard conversations, reading widely, trial and error in your own life, a willingness to tinker — these are the inputs. There's no shortcut and no supplement.

It's not unusual to meet people in their nineties who are still full of life and unmistakably playful. I'd argue playfulness is the single clearest marker of genuine youth. Watch for the moment someone loses it. As people surrender that playfulness, they go dry and stale, regardless of what their birth certificate or their wearable says.

None of this is an argument against aging. There's enormous value in lived experience and in knowledge accumulated over decades. Some of my favorite conversations are with people who have navigated the full catalog of life's challenges and come out the other side still standing. Watching someone walk gracefully despite everything they've carried is, frankly, one of the more motivating things I get to see.

3-Point Summary

• You have four ages, not one, and they rarely agree. Chronological is the only honestly measurable number. Biological, functional, and emotional drift apart from it and from each other, which is why you can meet an old man who never grew up and a young woman who grew up too soon.

• The trendy age is the least useful one. Biological age clocks repackage real markers — inflammation, metabolic health, tissue damage — into a single score with poor repeatability and no clinical utility. Manage the markers; hold the score loosely.

• The two ages nobody sells you are the ones that matter. Functional age, measured by what your body can actually do, and emotional age, built through experience and preserved through playfulness, tell you far more about how you're really aging than any wristband.

3 Practical Takeaways

1. Test your function, not your wrist. Pick a couple of honest physical benchmarks — a loaded carry, a timed run, a strength standard for your age — and see which age bracket you'd actually hold your own in. Then train both ends: lift for strength, run for your vascular system. You need both, not the one you already like.

2. Treat the biological age number as entertainment, not a verdict. If you want to move it, ignore the readout and work the fundamentals underneath it — sleep, blood sugar, inflammation, movement. Don't let a volatile score on a device dictate how you feel about your health.

3. Protect your playfulness. Emotional age is the one fully in your hands. Keep reading, keep traveling, keep tinkering, keep having the hard conversations — and notice when stress is dragging you down a maturity stage and into an impulsive decision. The people who stay young are the ones who never stop playing.