Prediction equations for fat and fat-free body mass in adolescents, based on body circumferences

Background: Fat mass (FM) and fat-free body mass (FFB) are important parameters for assessing nutritional status, since they are associated with higher prevalence of excess body fat and malnutrition worldwide. Aim: To develop prediction equations for fat and fat-free body mass in adolescents using body circumferences. Subjects and methods: This cross-sectional study included 218 adolescents (10-16 years) with normal weight as defined by body mass index. FMPred and FFBPred were estimated using stepwise multiple linear regression, considering age and body circumferences. Response variables, FMBIA and FFBBIA were estimated using bioelectric impedance analysis (BIA). The accuracy of the prediction equations was evaluated using the coefficient of determination (R-2) and Akaike's Information Criterion (AIC). Results: The best prediction equations for males were FMPred = -7.114 - 0.592(age) - 0.958(wrist) + 0.191(hip) + 0.295(abdomen); R-2 = 0.552; AIC = 416.04 and FFBPred = - 52.180 + 1.913(age) + 1.954(wrist) + 1.635(forearm); R-2 = 0.869; AIC = 578.24. For females, the best equations were FMPred = -17.580 - 0.678(wrist) + 0.221(abdomen) + 0.241(hip) + 0.202(proximal thigh) - 0.228(calf); R-2 = 0.838; AIC = 415.36 and FFBPred = -31.066 + 0.90(age) + 1.090(wrist) - 0.139(abdomen) + 0.326(hip) + 0.632(calf); R-2 = 0.878; AIC = 512.48. Conclusion: The equations developed to estimate fat body mass in females and fat-free body mass in both genders had high adjusted coefficients of determination and are therefore preferable to those derived using BIA.