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Utility of different body composition indicators: demographic influences and associations with blood pressures and heart rates in adolescents (Heartfelt Study)

Primary objective: To compare the utility of 10 commonly used body composition indicators (BCIs) in relation to demographic characteristics and cardiovascular risk factors. Research design: A cross-sectional, school sample was studied. Subjects: Three hundred and eighty-four Black, White and Hispanic adolescents 11–16 years of age from Houston, Texas, USA (Heartfelt Study) were studied. Methods: BCIs include impedance and skinfold estimates of fat-free mass (FFM); fat mass (FM) and per cent body fat (PBF); resistance mass index (RMI); body mass index (BMI); and waist and abdomen circumferences. The cardiovascular risk factors (blood pressures/heart rates) are summarized by factor analysis. Sexual maturity was clinically assessed. Results: Two distinct classes of BCIs emerged with respect to demographic influences: (1) RMI, impedance and skinfold estimators, for which sexual dimorphism is evident, and (2) BMI and circumferences, for which it is not. All BCIs were strongly related to general (systolic) blood pressure, but only body fat variables were related to heart rates. Skinfold-derived FM, PBF and mid-body circumferences were the variables most strongly related to cardiovascular risk factors. Conclusions: RMI, impedance or skinfold estimators are necessary for research requiring an accurate description of body composition changes during adolescence and for assessing the role of lean and fat tissue in disease aetiology. A 2–skinfold method is just as effective as the more complicated impedance. Mid-body circumferences are closely related to blood pressures and heart rates, suggesting their importance as indicators of abdominal fat in adolescents.