Is waist circumference per body mass index rising differentially across the United States, England, China and Mexico?

BACKGROUND/OBJECTIVES: Little is known about whether waist circumference (WC) has increased disproportionately relative to body mass index (BMI) around the world. SUBJECTS/METHODS: Data came from the US National Health and Nutrition Examination Survey (1988-1994 and 2007-2010), Health Survey for England (1992-1993 and 2008-2009); the Mexican Nutrition Survey (1999) and the Mexican National Health and Nutrition Survey (NHNS 2012); and the China Health and Nutrition Survey (1993 and 2011). Country-and sex-stratified (for the United States, also race-/ethnicity-stratified) multivariable linear regressions were used to estimate mean difference in WC over time relative to BMI at specified overweight and obesity cutoff points, adjusting for age and survey year. RESULTS: Although mean WC and BMI shifted upward over time in all age-sex subpopulations in all four countries, trends in overweight prevalence were less consistent. However, WC relative to BMI increased at varying magnitudes across all countries and subpopulations, except US Black men. The magnitude of increase was largest for women in the youngest age group (20-29 years), particularly for women in Mexico (+6.6 cm, P<0.0001) and China (+4.6 cm, P<0.0001) (holding BMI constant at 25 kg/m(2)). For men, the increase was primarily evident among Chinese men (+4.8 cm, P<0.0001). CONCLUSIONS: WC has increased disproportionately over time relative to overall body mass across the United States, England, Mexico and China, particularly among young women, with the largest increases occurring in the middle-income countries of Mexico and China. These patterns are potentially a cause for concern especially for countries undergoing rapid economic and nutritional transitions.