Learn · Longevity science · Updated June 2026

What Is Biological Age — and Why It Matters More Than Your Birthday

Your calendar age counts the years since you were born. Your biological age estimates how old your body actually functions — how well your metabolism, cardiovascular system, skin, and cells are holding up against time. Two people who are both 40 on paper can be a decade apart biologically, and the difference shows up in energy, body composition, skin, recovery, and long-term disease risk.

How biological age is estimated

There's no single "age organ" to read — researchers estimate biological age by combining markers that track aging across systems:

Blood biomarkers — published models such as PhenoAge combine markers like fasting glucose, CRP (inflammation), and kidney/liver values with age to estimate physiological aging.
Epigenetic clocks — DNA-methylation patterns (e.g., Horvath, GrimAge) that shift predictably with age.
Functional and lifestyle markers — body composition, sleep quality, activity, resting heart rate, HRV, and glucose stability all correlate with the pace of aging.
Subjective vitality — how old you feel day-to-day tracks meaningfully with health outcomes, which is why Jevity measures FeelAge™ alongside objective signals.

What actually moves your biological age

The encouraging science: biological age is not fixed. The levers with the strongest evidence are unglamorous and powerful — consistent sleep, resistance training, protein-adequate nutrition, glucose stability, not smoking, and stress regulation. We break these down in how to lower your biological age naturally.

Biological age vs. metabolic age vs. felt age

You'll see several "ages" used in longevity medicine. At Jevity we track them as a stack: TrueAge™ (overall biological age), MetaboAge™ (your metabolic engine — glucose stability, body composition, activity), GlowAge™ (visible skin-aging trajectory), and FeelAge™ (daily felt age). One number hides information; a stack shows you where aging is happening so the fix can be specific.

Estimate your biological age — free, 2 minutes

Answer a few lifestyle questions and get your Jevity Score™, TrueAge™ estimate, and a personalized protocol preview.

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Frequently asked

Is a lifestyle-based estimate accurate? It's a useful starting estimate, not a lab result. Blood-biomarker and epigenetic testing tighten the picture — Jevity's roadmap fuses at-home lab panels into your TrueAge™ as they launch.

How fast can biological age change? Intervention studies have measured meaningful shifts in months, not decades — sleep, training, and metabolic improvements compound quickly.