Relative validity of different methods to assess body composition in apparently healthy elderly women

Body composition was assessed by means of densitometry, anthropometry and bioelectrical impedance in 28 healthy, elderly females, aged 67-78 years. Underwater weighing was used as the reference method. Mean body mass index (BMI) was 26.3 +/- 3.4 kg/m2. Body fat percentage from body density was 39.6 +/- 5.6%. The fat-free mass (FFM) from body density was 41.0 +/- 5.4 kg. Mean predicted FFM using different prediction formulas from the literature ranged from 38.8 +/- 4.2 to 46.3 +/- 5.3 kg. The differences between FFM from densitometry and FFM using either prediction equation were highly correlated, thus part of the difference is probably due to an error in the reference method. The different prediction equations revealed rather good relative validity, compared to the densitometric method, with the exception of equations based on skinfold measurements developed in younger reference populations. Age-specific prediction equations based on BMI and bioelectrical impedance measurement may be used to assess body composition in the elderly. Prediction equations using skinfold thickness measurements are less appropriate for this purpose.