Metabolic Age

Your Metabolic Age is a single number that says how your body’s everyday health signals compare to what is typical for your age and sex. If your markers are stronger than the average person your age, it reads younger; if they are struggling, it reads older.

It is not a bloodwork test or a medical diagnosis, and it is not a fixed fact about you. It is an honest estimate built from the things you can actually change: how you recover, sleep, move, and eat.

We start at your real age, then nudge it up or down based on how each of your markers compares to its age-and-sex-expected norm:

• Heart-rate variability (HRV), the strongest signal of autonomic fitness. Measured against published age norms.
• Resting heart rate, a lower rate reads younger and fitter.
• Body composition, body fat % when you enter it, otherwise BMI, used gently.
• Sleep, consistently good sleep reads younger.
• Daily activity, habitual movement reads younger.
• Nutrition quality, a consistently high-quality diet reads younger.

Each marker can only move the number so far, and the total is capped, so no single reading can swing your age wildly. The estimate is always anchored to your real age.

HRV varies enormously between healthy people, which is why your daily recovery is scored against your own baseline, not against others. Metabolic Age treats HRV humbly: being within a normal range of your age norm reads neutral, so a perfectly healthy value never makes you "years older".

Until we have enough nights of heart-rate data to be honest, the number stays in a "calibrating" state instead of showing a confident figure. Better to wait than to show a wrong number.

The same things that make you feel good move this number: sleep well and consistently, keep moving, fuel your training, and give your body real recovery days. Because nutrition quality feeds in, what you eat literally shifts your Metabolic Age over time.

Adding your body fat % in the card sharpens the composition read. It is optional and never read from Apple Health.