How is Body Age calculated? Your biological age from an Apple Watch
Body Age (biological age) estimates how young or old your body actually is from your physiological data — not your calendar age. Vita (100old.app), an iOS app, computes your Body Age from VO₂max, resting heart rate, HRV, sleep and step trends, and lets you drill into how each driver affects it. It works with just an Apple Watch and is free to download.
How Body Age is calculated
Vita takes five signals strongly tied to longevity and health: VO₂max (cardiorespiratory fitness), resting heart rate (RHR), heart-rate variability (HRV), sleep quality, and daily activity (steps). Each factor is compared against age norms and turned into a positive or negative contribution to your Body Age, then combined into a single number. Because the data updates daily, your Body Age moves with your lifestyle — it's not a one-off reading.
What each factor measures
Why Body Age is worth watching
Any single metric is hard to feel. Body Age compresses them into one number you can understand and track: sleep more this month, push your fitness up, and your Body Age drops — you see the payoff immediately. Vita's AI coach also reads these factors and tells you what to change next to bring it down further.
How it differs from WHOOP Age
WHOOP has its own physiological-age feature (WHOOP Age, inside Healthspan) and it's a solid one — but it analyses only what WHOOP collects. Vita's Body Age differs structurally by fusing sources: it reads WHOOP directly when you wear one, Apple Health always contributes (steps, VO₂max, weight — dimensions WHOOP doesn't capture), and markers from uploaded lab reports can sit alongside for context. The result: the estimate covers more of your physiology, survives switching wearables, and — for people wearing both a WHOOP and an Apple Watch — the two sources cross-validate, making the trend more trustworthy. Every driver is drillable, and the AI coach will tell you (in English or Chinese) which one is currently costing you the most years.
How to lower your Body Age, ordered by speed of payoff
- Fix sleep first (fastest, 2–4 weeks) — a consistent sleep window and no late alcohol move the sleep driver and HRV before anything else
- Add Zone 2 cardio (4–12 weeks) — 150 minutes/week at conversational pace pulls resting heart rate down and HRV baseline up
- Then add intensity (3–6 months) — 1–2 weekly interval sessions (e.g. 4×4 minutes) push VO₂max, the heaviest driver in the model
- Keep moving daily — going from sedentary to ~8k steps matters more than stacking 8k into 12k
- Be patient: Body Age moves on a monthly timescale. Week-to-week wobble is noise; the quarterly trend is the signal
FAQ
What's the difference between Body Age and my real age?
Your real age is time since birth; Body Age estimates 'what age your body performs at' from physiological data like VO₂max, HRV, resting heart rate, sleep and activity. People who train and sleep well often have a Body Age below their real age.
Is this the same as WHOOP Age?
Same family of estimate, different inputs: WHOOP Age uses WHOOP's own data only. Vita's Body Age fuses WHOOP + Apple Health and can sit lab-report markers alongside — broader coverage, and it keeps working if you change wearables.
Can I get Body Age without a WHOOP band?
Yes. Vita reads the data it needs from Apple Health via your Apple Watch + iPhone — no WHOOP required.
Is Body Age accurate?
It's a trend estimate based on population norms — not a medical diagnosis, and not a lab DNA-methylation test. Its value is longitudinal tracking: the direction your lifestyle moves the number matters more than the absolute value.
How fast can my Body Age drop?
Sleep-related drivers respond in 2–4 weeks; resting heart rate and HRV in one to three months; VO₂max is the slowest but heaviest driver — expect 3–6 months of consistent training to move it meaningfully. Quarterly trends beat weekly wobble.
Where can I see my Body Age?
Download Vita free on the App Store, connect Apple Health (or WHOOP), and you'll see your Body Age and each factor's contribution within minutes.
Metric explanations on this page are based on published research — see our sources & methodology.