AGE-RELATED VARIABILITY IN BODY-COMPOSITION METHODS FOR ASSESSMENT OFPERCENT FAT AND FAT-FREE MASS IN MEN AGED 20-74 YEARS

Introduction: assessing body composition is important because of the a ssociation between excess body fat or obesity and the increased risk f or coronary artery disease, diabetes, hyperlipidaemia and hypertension . Methodological differences among indirect body composition technique s are a source of variability that can affect estimations of fat-free mass (FFM) or percent fat, especially for different age groups. Purpos e: this study examined the effect of age on the estimation of body com position by three methods based on the two-component model. One hundre d and fifty-three men were placed into 5-year age groups from 20-24 to 70-74 years. Body composition was assessed by hydrodensitometry (unde rwater weighing; UWW), K-40 spectroscopy (K40) and anthropometry. Resu lts: day-to-day reliability was excellent for each method. Correlation coefficients between methods, independent of age, ranged from r = 0.7 1 (K40 and UWW) to r = 0.83 (UWW and anthropometry) for % fat and from r = 0.76 (K40 and anthropometry) to r = 0.90 (UWW and anthropometry) for FFM. Correlations between techniques weakened and showed greater v ariability as age increased. UWW produced the highest % fat and lowest FFM for the different age groups, while K40 and anthropometry yielded similar body composition values. AU three methods detected age-relate d differences in % fat; however, only UWW determined a significant age effect in FFM. The greatest discrepancies between the methods occurre d for the oldest age groups (60-74 years), but noticeable differences began occurring after the age of 40. Conclusions: each method produced reliable data. Care should be taken when choosing any method based on the two-component model, especially when different age groups are bei ng examined, since estimating % fat and FFM is dependent on the age-re lated chemical composition of an individual and the limitations of eac h method.