Sex differences in the secular change in waist circumference relative to body mass index in the Americas and England from 1997 to 2020.

Objective: To quantify changes over time in waist circumference (WC) relative to body mass index (BMI) by sex in the Americas (U S, Mexico, Chile, Peru) and England.

Methods: Data from adults aged 25-64 years between 1997 and 2020 was analysed; US data was stratified by racial-ethnic groups. Sex-specific BMI and WC means, and obesity and abdominal obesity prevalence, were compared between the first and last surveys. Using data from all survey years, secular changes across the BMI and WC distributions were estimated applying quantile regression models. BMI was added as a predictor of WC to estimate secular changes in WC relative to BMI. Interaction terms were included in all models to evaluate differences by sex.

Results: BMI and WC (except Peru) showed larger secular increases at the upper-tails of the distributions in both sexes. Increases at the 50 and 75 WC centiles relative to BMI were more pronounced in women than in men, with larger increases in US non-Hispanic whites and in England. In men, increases in WC independently of BMI were most evident in Mexico.

Conclusions: Disease risk associated with visceral fat, is potentially underestimated by national surveillance efforts that quantify changes only in BMI.