What waist_circumference measures
waist_circumference is the latest waist measurement on the day, in metres.
| Field | waist_circumference |
|---|---|
| Unit | Metres |
| Reported | On days with a reading. The latest reading of the day is kept. |
| Window | Midnight to midnight, profile local time |
| Wearable required | No |
| API | GET /api/v1/profile/biomarker/{externalId}?categories=body&types=waist_circumference plus a date range |
| Webhook | BiomarkerCreatedIntegrationEvent. Entries update in place, upsert on id. |
It is a point-in-time reading with periodicity none. Take the most recent entry as the current value.
Data sources
| Platform | Record | Notes |
|---|---|---|
| iOS, HealthKit | waistCircumference | Manual entry in the Health app, or a measurement app that writes it |
| Android, Health Connect | Not read | |
| Direct integrations | Provider-dependent | |
| Phone only | Manual entry on iOS |
How Sahha calculates waist_circumference
- Pick one source for the day within the body category.
- Keep the latest reading from that source on the day, converted from centimetres to metres.
Absence means no reading that day.
Interpreting the value
It is the cheapest useful body composition proxy. Waist circumference tracks visceral fat better than BMI and needs only a tape measure [1]. Change over months is the signal.
Measurement technique dominates. Level of the tape, breath, and time of day change it by centimetres. A feature that collects it should show the user how to measure.
Related scores and insights
Waist circumference is not a score factor and has no trend or comparison insight.
Use cases
A monthly measurement prompt with a trend. Ask on the first of the month, show the last six values. Sparse by design.
GET /api/v1/profile/biomarker/{externalId}?categories=body&types=waist_circumference&startDateTime=2026-03-03&endDateTime=2026-09-03Waist-to-height ratio. Divide by the latest height for a single number that guidelines increasingly prefer to BMI. Both inputs are in metres.
Limitations
- iOS only, and manual.
- Point in time. Do not aggregate across days.
- Absence is not zero.
Related guides
- Weight, height, and BMI for the height used in the ratio
- Body fat for the scale-based composition fields
- Data dictionary in the developer docs
References
- Ross R, Neeland IJ, Yamashita S, et al. Waist circumference as a vital sign in clinical practice: a consensus statement from the IAS and ICCR Working Group on Visceral Obesity. Nature Reviews Endocrinology. 2020;16(3):177-189. https://doi.org/10.1038/s41574-019-0310-7