NHANES (CDC) — derived WHtR percentiles
About this reference
No published study provides sex- and age-stratified WHtR percentile tables for US adults. NHANES collects both waist circumference (BMXWAIST) and standing height (BMXHT) in the body measures examination. FitnessNorms derived WHtR percentiles by downloading public XPT microdata files for three NHANES blocks, merging body measures with demographics, and computing weighted empirical quantiles (P5, P25, P50, P75, P95) for each sex × 5-year age bracket from 20–24 through 80+. Three cycles were pooled to improve tail stability: 2015–2016 (BMX_I / DEMO_I, weight WTMEC2YR), 2017–March 2020 (P_BMX / P_DEMO, weight WTMECPRP — the CDC-prescribed pre-pandemic weight), and 2021–2023 (BMX_L / DEMO_L, weight WTMEC2YR). Pooling used equal-cycle weighting (each cycle's MEC weight divided by 3), which is a FitnessNorms design choice made after comparing the 2021–2023-alone table against the pooled table. The two tables showed no cell with a median difference exceeding 0.02, and no structural discontinuity was detected across the pandemic break, making pooling defensible for WHtR. The 2021–2023-alone output is retained as an internal sensitivity check. Weighted quantiles were computed using linear interpolation on the empirical cumulative distribution (analogue of Type 7). Sampling weights were applied to produce weighted percentile estimates; survey-design standard errors were not computed (this is an internal derivation, not a peer-reviewed publication).
Known limitations
- US population only — percentiles reflect the US adult population, which has one of the highest obesity rates globally. US WHtR medians are systematically higher than reference values from leaner populations such as Colombia or parts of East Asia.
- This is an internal derivation by FitnessNorms from CDC public microdata, not a peer-reviewed publication. Weighted empirical quantiles are used; survey-design-correct standard errors are not reported.
- Equal-cycle pooling (dividing each cycle's weight by 3) is a FitnessNorms design choice. CDC does not prescribe a pooling method for this specific combination of releases, particularly across the pandemic break.
- RIDAGEYR is top-coded at 80 in NHANES public data; the 80+ bracket includes all participants aged 80 and over.
- Cross-sectional design: values reflect population averages at the time of survey, not individual trajectories.