Open composite index methodology

Some of our tools are open composite indices, single 0 to 100 scores built from several inputs. The whole point is that they are transparent: we publish the inputs, how each is scored, the weights, and the evidence behind them. You can reconstruct any score yourself. That openness is the opposite of the hidden scores inside proprietary wearables and testing services.

How a score is built

1. Sub-scores (0 to 100). Each input becomes a 0 to 100 sub-score where higher is always more favourable, via a documented, clamped linear mapping between stated anchor points.
2. Weights and evidence tiers. Weights sum to 100%. Every input is tagged T1 (strong, outcome-linked evidence), T2 (moderate/surrogate) or T3 (mechanistic). No single input exceeds ~30%, and a weak (T3) input never outweighs a strong (T1) one.
3. Aggregation.The index is the weighted average of the sub-scores. Some tools also show a centred “pace” number, which is just a display transform of the same index.
4. Missing data. Leave an input blank and the weights renormalise across what you provided, with a reduced-confidence flag. We never substitute a value that flatters or penalises you.

What these scores are not

A composite index here is a transparent tool for self-tracking. It is not a medical test and has not been validated against health outcomes. No index outputs a mortality estimate, life-expectancy figure or disease probability; body- composition inputs are capped and never dominate; and none produces medication or supplement advice. A low sub-score points to a modifiable lever. It is never a judgement on you.

Versioning & changelog

Weights and mappings are part of the public contract: they never change silently. Every change bumps the version and is recorded here.

• Metabolic Fitness Index v2.0.0 (2026-08-09), rebuilt on a standard blood panel. v1 ran on the CGM consensus metrics — time in range, glucose variability and GMI — and required all five inputs, so a reader without a continuous glucose monitor received no score at all. v2 replaces those three with HbA1c, fasting glucose and a HOMA-IR term from fasting insulin, adds the triglyceride:HDL ratio, and keeps waist-to-height and resting heart rate. GMI is itself a CGM-derived estimate of HbA1c, so the swap is to better evidence of the same quantity rather than a substitute for it. The index now needs any three of its six inputs and renormalises across what is present, per §4.5. The triglyceride:HDL anchors are sex-specific (1.7 mmol/L for men, 0.9 for women): the familiar 3.0–3.5 figures are mg/dL, and one shared anchor would misread every woman. See the tool page for the full weights and anchors.
• Metabolic Fitness Index v1.0.0 (2026-07-22), initial release. Superseded by v2.0.0 above.
• Pace of Aging Index v1.0.0 (2026-07-22), initial release. Cardio fitness (VO₂max) is an optional input pending a verifiable fitness-age source; grip and HRV are optional too. See the tool page.
• Recovery Readiness Index v1.0.0 (2026-07-22), initial release. Weights adjusted from the proposed HRV 40% to HRV 30 / resting HR 25 / sleep 25 / breathing 20 to respect the 30% single-input cap. See the tool page.