How Biological Age Became the New Status Symbol

I got a pleasant surprise at my gym last month. According to the latest fitness assessment at Fred Fitness, my biological age had dropped from 36 to 27. Nine years younger! (My actual age is 46.)

Fred Fitness, a new AI-powered gym in Santa Monica, calculates biological age based on four key factors: strength, flexibility, metabolism, and cardio fitness. I’d improved across the board.

Still, when I looked in the mirror, I had the same receding hairline. I wasn’t sure what I’d really changed — or whether any of it mattered.

That’s the strange, slightly thrilling promise of biological age: a number that says you're getting younger, even if your reflection disagrees.

“I was so much older then, I’m younger than that now.” -Bob Dylan

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What is Biological Age?

In the not-so-distant past, you had one age: the number of candles on your birthday cake. Today, you might have three or four—depending on which app, wearable, or lab you’re using.

Welcome to the era of biological age, a metric that aims to measure how well you're aging on a cellular level. These tools use various biomarkers and methods to estimate the functional capacity and health of an individual's tissues and organs.

Apps like Humanity and GeroSense estimate biological age by analyzing data from wearables, smartphones, and even blood tests. Humanity gives you a daily "Humanity Score" to nudge you toward longevity-friendly behaviors.

Direct-to-consumer lab services like Function Health look at blood biomarkers that reflect how efficiently your cells repair damage, maintain function, and defend against age-related decline.

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Is Biological Age the New Six Pack?

The concept of biological age has been around for a long time in scientific research. Now, with today’s consumer health tools, it’s entering the mainstream.

People are sharing their biological age score in group chats, Instagram Stories, and LinkedIn. They’re using hashtags like #AgingBackwards (please don’t do this).

For a certain demographic — think tech founders, venture capitalists, and Equinox members who moonlight as amateur longevity researchers — biological age is more than a health metric. It’s a flex.

Public figures like Bryan Johnson, founder of Blueprint, are openly broadcasting their biological age. I wouldn’t be surprised if some biohackers are sharing their biological age on their dating profiles (“I’m 45 but my VO2 max says I'm 27.")

It’s easy to see the appeal. Biological age sits at the intersection of:

• Science

• Aesthetics

• Wellness culture

• Self-optimization

Biological age is quantifiable, shareable, and social. It signals mastery over your body. It’s a digital-age badge of health capital — no six-pack required.

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What does the Science Say?

Invasive tests that require blood draws or saliva tend to be more accurate than wearables or app-based systems. The most reliable measure of biological age, Klemera and Doubal’s method (KDM), looks at 16 physical and 9 biochemical markers. It has been shown to predict the risk of all-cause mortality over a decade.

Consumer tools for measuring biological age are less reliable:

• Different apps and labs give wildly different results.

• You could "age" or "de-age" by seven years just by switching apps. It’s the biological version of finding good lighting.

• No one knows yet whether slowing biological age scores truly translates into longer, healthier lives — or just better test results.

In my case, I’m pretty sure I didn’t become nine years younger overnight. I didn’t discover the fountain of youth. I just figured out how to game the fitness assessment at my gym.

Then again, precision isn’t really the point. The real value of biological age tracking is motivation.

People see their biological age and start walking more, eating better. Getting better sleep.

Research says graceful aging has more to do with lifestyle than genetics. People who experience high stress, use tobacco and drink alcohol, are socially isolated, lead a sedentary lifestyle and consume a low-quality diet are more likely to develop early-onset illnesses and premature death.

Digital health leaders talk about closed-loop feedback cycles. Just like a smart thermostat adjusts temperature based on your behavior, apps and wearables use your real-time data to nudge you toward healthier patterns.

Biological age tracking can be a powerful driver of adaptive feedback loops that inspire healthy behavior change.

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How it’s Measured

Depending on the method, biological age scoring can be invasive, expensive, or easy enough to track daily.

Here’s how the most common approaches stack up:

1. DNA methylation patterns / epigenetic clocks estimate biological age by examining chemical tags that accumulate on DNA over time, influencing gene expression.

2. Blood biomarker panels assess biological age using panels of blood biomarkers—often including glucose, triglycerides, CRP, cholesterol, liver enzymes, and more.

3. Gut microbiome analysis is based on the gene expression profile of your gut microbiome.

4. Wearables and app-based systems use continuous tracking of lifestyle data—heart rate variability (HRV), sleep quality, resting heart rate, activity levels, and respiratory rate—to estimate biological age.

5. Hybrid approaches may combine several different inputs: Metabolic health, wearable data, nutrition responses, and/or genetic information to deliver biological age scores.

There are also tools like the Heart Age Calculator, which estimates your heart age to assess your risk of a heart attack or stroke.

In general, the more invasive biological age tests (DNA methylation, blood biomarkers) are more accurate than apps and wearables. But even these have limitations. They don’t include clinical variables like blood pressure or glucose metabolism. They haven't been evaluated by independent experts.

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What Really Matters

So, should you get your biological age tested?

Sure — if it motivates you to move more, sleep better, and eat smarter.

But remember: the real markers of a life well-lived aren’t buried in your mitochondria. They’re found in the people you laugh with, the projects you throw yourself into, the mornings you wake up grateful to still be here.

The goal isn’t just to live longer. It’s to live better. So go ahead and enjoy that slice of birthday cake.

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Thank you for reading this week’s edition of Vitamin Z.

Until next time,

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By Daniel Zahler

Hi there and thanks for reading. I created Vitamin Z to share my research on health and wellness, longevity and healthy aging, and ways to optimize cognitive, physical and emotional health. I have interviewed hundreds of doctors and health system leaders to help my clients spot trends and opportunities in healthcare. I am an advisor to Noom, a digital health company helping millions live better longer, and a project leader at GLG, where I advise global business leaders on healthcare innovation.

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