SKELETAL DIFFERENCES BETWEEN BLACK-AND-WHITE MEN AND THEIR RELEVANCE TO BODY-COMPOSITION ESTIMATES

Skeletal differences exist between closely matched Black and White wom en, although it is unknown if similar differences also exist between B lack and White men after controlling for age, body weight, and stature . The aim of this study was twofold: to test the hypothesis that Black men have greater bone mass, higher bone mineral density, and longer l imbs compared to White men of similar age, weight, and height; and sec ond, to establish if ethnic variation in skeletal characteristics has an impact on the models upon which three widely used methods for estim ating total body fat are based. Twenty-four healthy Black men were mat ched by age(+/-5 years), height(+/-3 cm), and weight(+/-2 kg) to 24 he althy White men. Skeletal characteristics and body composition were st udied using anatomical and compartment estimates derived by anthropome try, (H2O)-H-3 dilution, hydrodensitometry, whole-body K-40 counting, and dual photon systems. Black men had greater bone mineral mass (P = 0.007), higher bone density (P = 0.054), longer femurs (P = 0.002), lo nger anthropometric arm and thigh lengths (P = 0.001 and P = 0.002, re spectively), lower spine to femur ratio (P = 0.004), and similar spine length (P = 0.271) compared to White men. Total body fat and fat-free body mass (FFM) were estimated in the men using a four-compartment mo del. Black and White men had similar total body fat, K (TBK), water (T BW), and FFM. Density of FFM and TBK/FFM were also similar between Bla ck and White men, suggesting that current two-compartment hydrodensito metry and TBK models for estimating fat may not require adjustments fo r ethnicity. The TBW/FFM ratio, which is the main assumed steady-state relation for the two-compartment TBW method of estimating fat, was mo destly increased (P = 0.05) in Black men x ($) over bar +/- SD, 0.744 +/- 0.018) compared to White men (0.732 +/- 0.021). These results conf irm that Black and White men differ significantly in some skeletal cha racteristics and these differences have implications in the study of b oth osteoporosis and human body composition. (C) 1994 Wiley-Liss, Inc.