Sex and ethnic differences in validity of self-reported adult height, weight and body mass index

Abstract

Objectives: Describe self-reported and measured height, weight, and body mass index (BMI) stratified by sex and ethnicity in the United States, explore ethnic variations in the likelihood of under-reporting BMI, and investigate pathways linking race/ethnicity to the underassessment of BMI. Design: An observational study. Setting: The entire United States. Patients or Participants: Data were from the 2007-2008 National Health and Nutrition Examination Survey, a nationally representative sample of non-institutionalized civilian Americans. Main Outcome: Objectively measured and subjectively reported BMI. Measures: Independent variables include race/ethnicity (non-Hispanic Whites, non-Hispanic Blacks, Hispanics, and others), sex, age groups (age 20-29, 30-49, 50-69, and ≥70), marital status (currently married vs other marital categories), education (less than high school, high school graduate or equivalent, some college, college graduate or above), and poverty income ratio (PIR). Results: This study confirmed that the use of reported BMI led to underestimates of the population prevalence of overweight and obesity due to the general tendency towards over-reporting height and under-reporting weight. Women were more likely than men to under-report BMI. And Whites were more likely than Blacks and Hispanics to underreport BMI. Other factors positively associated with higher likelihood of under-reporting of BMI included overweight and obese weight status, aged ≥60 years, and college education. Among women, family income was an additional positive covariate. Conclusions: The results from this study underscore the need for frequently monitoring ethnic differences in validity of reported BMI and highlight the care which needs to be taken in making comparisons across sociodemographic groups based on reported BMI.