PAPER Body composition estimates from NHANES III bioelectrical impedance data WC Chumlea 1 , SS Guo 1 *, RJ Kuczmarski 2 , KM Flegal 3 , CL Johnson 3 , SB Heymsfield 4 , HC Lukaski 5 , K Friedl 6 and VS Hubbard 7 1 Department of Community, Health Wright State University School of Medicine, Dayton, Ohio, USA; 2 National Institutes of Health Division of Digestive Diseases and Nutrition, NIDDK, Bethesda, Maryland, USA; 3 Centers for Disease Control and Prevention, National Center for Health Statistics, Division of Health Examination Statistics, Hyattsville, Maryland, USA; 4 Obesity Research Center, St Lukes-Roosevelt Hospital, Columbia University, New York, USA; 5 US Department of Agriculture, Agriculture Research Service, Grand Forks HNRC, Grand Forks, North Dakota, USA; 6 Military Operational Medicine Program, Military Medical Research and Materiel Command, Frederick, Maryland, USA; and 7 National Institutes of Health, Division of Nutrition Research Coordination and Nutritional Sciences Branch, NIDDK, Bethesda, Maryland, USA BACKGROUND: Body composition estimates for the US population are important in order to analyze trends in obesity, sarcopenia and other weight-related health conditions. National body composition estimates have not previously been available. OBJECTIVE: To use transformed bioelectrical impedance analysis (BIA) data in sex-specific, multicomponent model-derived prediction formulae, to estimate total body water (TBW), fat-free mass (FFM), total body fat (TBF), and percentage body fat (%BF) using a nationally representative sample of the US population. DESIGN: Anthropometric and BIA data were from the third National Health and Nutrition Examination Survey (NHANES III; 1988 – 1994). Sex-specific BIA prediction equations developed for this study were applied to the NHANES data, and mean values for TBW, FFM, TBF and %BF were estimated for selected age, sex and racial-ethnic groups. RESULTS: Among the non-Hispanic white, non-Hispanic black, and Mexican-American participants aged 12 – 80 y examined in NHANES III, 15 912 had data available for weight, stature and BIA resistance measures. Males had higher mean TBW and FFM than did females, regardless of age or racial-ethnic status. Mean TBW and FFM increased from the adolescent years to mid- adulthood and declined in older adult age groups. Females had higher mean TBF and %BF estimates than males at each age group. Mean TBF also increased with older age groups to approximately 60 y of age after which it decreased. CONCLUSIONS: These mean body composition estimates for TBW, FFM, TBF and %BF based upon NHANES III BIA data provide a descriptive reference for non-Hispanic whites, non-Hispanic blacks and Mexican Americans in the US population. International Journal of Obesity (2002) 26, 1596 – 1611. doi:10.1038/sj.ijo.0802167 Keywords: body composition; obesity; BIA; NHANES; health surveys Introduction Overweight and obesity are increasing in the US population. 1,2 Excess adiposity is the major weight-related health concern up to the seventh decade of life, but an increased lifespan 3 indicates the importance of lean tissue loss and its association with frailty and sarcopenia in the elderly. 4,5 Fat and lean components of the body including total body fat (TBF), fat-free mass (FFM), and total body water (TBW) are important constituents that link obesity, aging, and chronic disease with subsequent morbidity and mortality. 6–8 There exists little accurate information at present on estimates of TBW, FFM, TBF, and percentage fat (%BF) for the US population as a whole. 9 – 11 Systems capable of reliably quantifying body com- position under controlled conditions, such as bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiom- etry (DXA), have been introduced and subsequently validated over the past two decades. 12,13 This technology and the increasing clinical and research importance of body com- position highlight the need for improved information on population estimates of TBW, FFM, TBF and %BF. Prior surveys and studies of body composition in the US population are based largely on anthropometric data including measures of body weight, stature, skinfold thick- *Correspondence: SS Guo, Lifespan Health Research Center, Department of Community Health, 3171 Research Blvd, Kettering Ohio, OH 45420, USA. E-mail: shumei.guo@wright.edu Received 11 October 2001; revised 15 May 2002; accepted 1 July 2002 International Journal of Obesity (2002) 26, 1596–1609 ß 2002 Nature Publishing Group All rights reserved 0307–0565/02 $25.00 www.nature.com/ijo