Development and validation of equations to estimate the body fat percentage in older adults using anthropometric measurements and portable a-mode ultrasound.

Background & Aims: Considering the importance of accurate methods for assessing body fat in older adults, this study aimed to develop and validate equations for estimating body fat percentage (%BF) using portable A-mode ultrasound (US) and anthropometric data in older adults.

Methods: A total of 149 healthy older adults (≥60 years old) were included in the cross-sectional study. Three-fourths (n = 111) were randomly assigned to the development sample and one-fourth to the validation sample (n = 38). Prediction equations using body mass index (BMI), sex, triceps, subscapular, abdominal, and anterior thigh subcutaneous fat thickness (SFT), and thigh circumference (TC) were generated for the development sample through multiple regression analysis and validated through the validation sample.

Results: Three equations were developed, the first with six parameters (R = 0.78; SEE = 3.05), the second with the same six parameters as the first plus thigh circumference (R = 0.80; SEE = 2.96), and the third with three parameters (R = 0.77; SEE = 3.19). There was no statistical difference between the %BF estimated by the equations developed using portable A-mode US and the %BF estimated by Dual-energy x-ray absorptiometry (DXA) in the development and validation samples. The three equations showed mean errors from 0.16 to 0.27 % and agreement limits from -5.89 to 6.28 %.

Conclusion: The best model had sex, BMI, triceps, subscapular, abdominal, anterior thigh SFT, and TC as predictor variables. The equation with only one US measurement (triceps SFT) could be an option for estimating %BF in clinical practice due to its practicality and quickness.