Biological Age: What We Learned from Testing Our Members

Your driver’s license says one number. Your blood says another.

Biological age testing measures how fast your body is actually aging — not based on when you were born, but based on how your organs, cells, and metabolic systems are functioning right now. Two 50-year-olds can have wildly different biological ages depending on their cardiovascular health, metabolic function, inflammation levels, and organ performance.

We calculated biological age for every member of Protocol’s practice. Across our full cohort, the average biological age was 3.8 years younger than chronological age. And 72% of members were biologically younger than their calendar age.

How we measured it, what the numbers mean, and — just as important — what they don’t.

What We Measured and How

Protocol uses the Levine PhenoAge algorithm, published in the journal Aging in 2018 and validated on two large national health surveys (NHANES III and NHANES IV) with mortality follow-up data. Despite the paper’s title referencing “epigenetic biomarker,” PhenoAge is not a DNA methylation test or an epigenetic clock. It’s a blood biomarker composite — a mathematical model built from nine routine lab values plus your chronological age.

The nine inputs:

1. Albumin — liver function and nutritional status
2. Creatinine — kidney function
3. Glucose — metabolic health
4. C-reactive protein (CRP) — systemic inflammation
5. Lymphocyte percentage — immune function
6. Mean cell volume (MCV) — red blood cell size, reflects nutritional and bone marrow health
7. Red cell distribution width (RDW) — variation in red blood cell size, an independent mortality predictor
8. Alkaline phosphatase — liver and bone health
9. White blood cell count — immune activity and inflammation

The algorithm combines these nine values with your chronological age to produce a single number: your estimated biological age. The model was originally trained to predict mortality — it identifies the combination of biomarker values that statistically predict how long a person is likely to live, independent of how old they are by the calendar.

A biological age lower than your chronological age means your biomarker profile looks like someone younger. Higher means the opposite.

Why These Nine Markers

PhenoAge works because it captures multiple systems at once. Glucose reflects metabolic health. CRP reflects inflammation. Albumin and alkaline phosphatase reflect liver function. Creatinine reflects kidney function. Lymphocyte percentage and white blood cell count reflect immune status. MCV and RDW reflect hematological health.

No single marker tells you much about how fast you’re aging. But the pattern across all nine — how your metabolic, inflammatory, hepatic, renal, immune, and hematological systems are performing together — produces a composite picture that predicts mortality better than chronological age alone.

That’s the logic: aging is not one process. It’s dysfunction accumulating across multiple organ systems. A test that captures dysfunction across nine systems will be more informative than one that measures only one.

What We Found Across Our Members

Most members had all nine biomarkers available for the full PhenoAge calculation. The remainder used a simpler fallback algorithm (Klemera-Doubal method) based on whichever biomarkers were available.

Across our full cohort:

• Average biological age gap: -3.8 years (biologically younger than chronological age)
• 72% of members had a biological age lower than their chronological age
• The remaining 28% were biologically older — their biomarker profiles resembled someone older than their calendar age

The range was wide. Some members were biologically 8-10 years younger. A smaller number were 2-4 years older. The average of -3.8 years masks real individual variation, which is the point: biological age is specific to you, not a population average.

What This Means — and What It Does Not

The caveats matter here, and we include them because intellectual honesty builds more trust than cherry-picked wins.

What we can say: The average Protocol member has a biomarker profile consistent with someone 3.8 years younger than their chronological age, as estimated by a validated, peer-reviewed algorithm.

What we cannot say:

• We cannot claim Protocol caused this result. This is cross-sectional data — a snapshot of where members are now, not a before-and-after comparison. We don’t have pre-membership biological age calculations for most members. Some of this -3.8 year gap likely existed before they joined.

• We cannot claim members will live longer. PhenoAge was validated against mortality data in large population studies. But we have no mortality data on our own members (thankfully). A younger biological age is associated with lower mortality risk in research populations, but we can’t extend that claim to our members specifically.

• This is a self-selected population. People who seek out a health optimization practice and pay for ongoing membership are, on average, more health-conscious, wealthier, and more educated than the general population. All three factors independently predict better health outcomes. The -3.8 year average reflects both what Protocol does and who Protocol attracts.

We report this number because it’s real, it’s ours, and it’s useful. We caveat it because claiming more than the data supports erodes trust — and trust matters more than impressive statistics.

Why Biological Age Matters for You

Even with those caveats, biological age testing answers a question that no single lab value can answer on its own: across your major organ systems, how is your body performing relative to your age?

That matters because the individual lab values that feed into PhenoAge are the same ones that predict disease. Elevated CRP predicts cardiovascular events. High fasting glucose predicts diabetes. Declining kidney function (rising creatinine) predicts renal disease. Abnormal liver enzymes predict hepatic disease. Elevated RDW predicts all-cause mortality even when every other lab looks normal.

Most annual physicals report these values individually, with binary “normal” or “abnormal” flags based on reference ranges. A CRP of 1.8 mg/L is “normal.” A fasting glucose of 99 mg/dL is “normal.” An albumin of 3.8 g/dL is “normal.” But all three together, in a 45-year-old, paint a picture that none of them paints alone. The composite tells you something the individual parts don’t.

That’s what biological age testing does. It takes nine data points your annual physical already collects (or should collect) and combines them into a single metric: your body is aging faster than expected, slower than expected, or right on track.

How We Use Biological Age at Protocol

Biological age is part of every member’s annual reassessment. It does three things:

1. Baseline context. When a new member joins, their biological age gives us an immediate signal about which systems are contributing to faster or slower aging. A member whose biological age is 5 years older than their chronological age likely has specific biomarkers driving that gap — maybe elevated CRP from chronic inflammation, maybe rising glucose from early insulin resistance. The calculation points us toward which protocols to prioritize.

2. Longitudinal tracking. As members complete protocols and improve specific biomarkers, their biological age should reflect those changes. If a member brings their CRP from 3.2 down to 0.8 through sleep optimization and dietary changes, that improvement shows up in the next calculation. It’s one way to measure whether the work is producing aggregate results, not just improvements in isolated numbers.

3. Motivation. “Your ApoB dropped from 130 to 78” is clinically meaningful but abstract for most people. “You are biologically 4 years younger than your age” is clinically meaningful and immediately understandable. Both matter. The second one tends to stick.

What Actually Moves Biological Age

Biological age is not a mystery. It’s a mathematical output of nine measurable inputs. If you want to move it, you move those inputs:

• Reduce inflammation (lower CRP) — sleep consistency, dietary modification, weight loss, stress management, and when indicated, statin therapy (which has anti-inflammatory effects independent of lipid lowering)
• Improve metabolic health (lower glucose) — the interventions from Protocol’s Metabolic Health protocol: meal sequencing, post-meal movement, resistance training, and CGM-guided dietary changes
• Protect kidney function (stable creatinine) — hydration, blood pressure management, avoiding nephrotoxins
• Support liver function (optimize albumin, alkaline phosphatase) — reduce alcohol, address fatty liver, ensure adequate protein intake
• Strengthen immune function (optimize lymphocyte percentage, WBC) — sleep, exercise, stress management, adequate nutrition

None of these are exotic interventions. They’re the same evidence-based protocols that improve individual biomarkers — they just also happen to improve the composite score that predicts how fast you’re aging.

The members in our practice who are 5-10 years biologically younger are not doing anything radical. They’re consistently managing their cardiovascular risk (ApoB below target), metabolic health (HOMA-IR in the optimal range), inflammation (CRP below 1.0), and body composition (adequate lean mass, low visceral fat). The fundamentals, executed with specificity and tracked with real data.

How to Get Your Biological Age Tested

If you want to calculate your own PhenoAge, you need the nine blood biomarkers listed above from a single blood draw. Most standard lab panels include some of them (glucose, creatinine, albumin, WBC). A few are less commonly ordered on routine panels (CRP, lymphocyte percentage, RDW, alkaline phosphatase, MCV). All are inexpensive — the full set costs $50-100 if ordered through a direct-to-consumer lab.

Several online calculators will compute PhenoAge from these inputs. The original algorithm is published and freely available.

The challenge isn’t the calculation. It’s interpretation — understanding which biomarkers are driving your result, which ones are modifiable, and what specific interventions will move them. A number without context is just a number. A number with a plan attached to it is actionable.

That’s the difference between getting a biological age result from an online calculator and getting one as part of a structured assessment. The number is the same. What you do with it determines whether it matters.

The Numbers Behind Our Numbers

We’re transparent about our data because that’s how evidence-based practice works. The full picture from Protocol’s dataset:

• ApoB optimal attainment: 27% at intake, 69% during membership — the full ApoB story
• Biological age: -3.8 years average, 72% biologically younger
• Cardiovascular risk: 95% maintained or improved on age-adjusted scoring
• A1c: flat — we cannot claim improvement (why honesty about this matters)

Real results include the numbers that moved and the ones that didn’t. We share both because you deserve to make decisions based on complete information, not a curated highlight reel.

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Ready to find out where you stand? Protocol’s Foundation Assessment measures what your annual physical misses — ApoB, HOMA-IR, DEXA body composition, VO2 max — and builds a specific action plan from the data.

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