The following analysis is based on the combined 2001-2006 data from the continuous National Health and Nutrition Examination Survey (NHANES) conducted by the National Center for Health Statistics (NCHS). The NHANES surveys are multi-stage probability samples of the non-institutionalized U.S. civilian population. Both physical measurement and self-reported height and weight information are collected in the NHANES for the same individuals, with the questionnaire preceding the physical examinations. Physical examinations take place in mobile examination centers and body measurements are based on standard protocols [20]. The overall unweighted NHANES response rates for the interview samples of the three continuous two-year surveys were 84% (2001-2002), 79% (2003-2004), and 80.5% (2005-2006) [21].
