Hi,

You're 45. Or maybe 32. Or 58.
Whatever number is on your ID... it tells you almost nothing about your real health trajectory.

Your chronological age tracks how long you’ve been alive.
But your biological age? That shows how fast your body is actually aging.

And now, we can measure it.

^{Chronological Age Is Outdated}

You and a friend might both be 50.
But one of you could have the biology of a 38-year-old. The other? A 65-year-old trapped in a younger body.

That 25-year biological age gap is the difference between resilience and decline.

The question is: which one are you?

The best part? Unlike your chronological age, your biological age is plastic - you can change it.

^{What Biological Age Really Measures}

Biological age is a composite of aging signals from across your body - DNA, inflammation, metabolism, fitness, immune system, and more.

Here are the most important categories:

1. Epigenetic Age (DNA methylation)

The most accurate biological clock we currently have.
Tracks changes in your DNA’s chemical tags that regulate gene expression.

Validated clocks include:

• Horvath clock

• GrimAge

• PhenoAge

• DunedinPACE (measures pace of aging)

Tests can be done at home using blood or saliva.

2. Telomere Length

Your chromosome “end caps” shorten with every cell division. Shorter = older.
Less precise than methylation clocks but still informative.

3. Inflammation Markers

Chronic low-grade inflammation ("inflammaging") accelerates aging.
Key blood markers: hs-CRP, IL-6, TNF-α

4. Metabolic Health

Glucose dysregulation and poor lipid profiles are major aging accelerators.
Key markers: fasting insulin, HbA1c, triglycerides, HDL, ApoB.

5. Mitochondrial Fitness

VO2 max, lactate threshold, and muscle recovery give you clues about energy resilience.

6. Immune Age

With age, immune function weakens.
Track: CD4/CD8 ratios, naïve T-cells, NK cell activity.

7. Functional Markers

Simple tests like grip strength, walking speed, and VO2 max outperform many lab tests in predicting mortality.

^{What These Metrics Actually Tell You}

1. Are you aging faster or slower than your age?
If you’re biologically younger: great - keep going.
If older: it’s a signal, not a sentence.

2. Which systems are aging fastest?
Newer tests show system-specific scores (metabolic age, immune age, inflammation age).

3. Are your interventions working?
You can’t manage what you don’t measure. Retest in 6-12 months to track progress.

4. What’s your trajectory?
DunedinPACE shows how fast you’re aging:

• 0.8 = aging 20% slower

• 1.0 = aging at average pace

• 1.2 = aging 20% faster

This is powerful feedback.

Next Week: How to Actually Measure It

In Part 2, we’ll break down:

• The best at-home tests to measure biological age

• Which markers you can track with your doctor or wearable

• What results actually mean

• And how to interpret “normal” vs “optimal” in the context of aging

Whether you're curious about epigenetic clocks or just want a practical starting point, we’ll make it clear - and include helpful links if you're ready to try one yourself.

Stay curious,
David
Founder, Longevity Enthusiasts

All insights in this newsletter are based on current longevity science and are written with guidance from leading research. For educational purposes only.

Disclaimer: This newsletter is for educational purposes only. It is not medical advice and should not replace consultation with a qualified healthcare professional.