What is biological age, and how is it different from your real age?

There are three broad families of biological-age estimates, at very different price points. Epigenetic clocks (DNA-methylation tests like Horvath/GrimAge-style panels) are the research gold standard — a lab test from a blood or saliva sample, typically $200–500 a run. Blood-biomarker ages (like PhenoAge-style calculations) derive an age from standard lab markers such as glucose, CRP and albumin. And wearable-based estimates — the family Vita, WHOOP Age and Garmin Fitness Age belong to — infer an age from physiological performance: VO₂max, resting heart rate, HRV, sleep and activity, each compared against age norms. Wearable estimates are the least clinical but the only ones that update daily and cost nothing extra — which makes them the practical choice for tracking direction.

The levers are unsurprising but their speed differs:

• Cardio fitness (VO₂max) — the heaviest driver in most models; months to move, worth the most
• Resting heart rate & HRV — respond in weeks to consistent aerobic work, sleep and less alcohol
• Sleep quality and consistency — the fastest lever; a few good weeks show up quickly
• Daily activity (steps) — a steady contributor; going from sedentary to 8k steps matters more than 8k→12k
• What doesn't work: supplements and biohacks with no effect on the underlying markers won't move a measurement-based age

WHOOP's Healthspan feature (WHOOP Age) estimates physiological age from WHOOP's own data — sleep, strain, heart-rate metrics — and it's a solid implementation of the wearable family. Vita's Body Age belongs to the same family with one structural difference: it fuses sources. It reads WHOOP data when you have one, Apple Health always, and lets clinical markers from uploaded lab reports sit alongside — so the estimate survives switching wearables and reflects more of your physiology. Neither replaces an epigenetic clock for research-grade precision; both beat any lab test for day-to-day feedback, because you can watch the number respond to how you actually live.

Vita's Body Age combines VO₂max, resting heart rate, HRV, sleep and step trends into a single number, and lets you drill into each driver's contribution — current value, 6-month average, and how much it adds or subtracts. Because it updates with your data, you can watch better training and sleep make your body "younger" over time, and the AI coach can tell you which driver is currently costing you the most years.