Body Mass Index (BMI) lacks precision in the evaluation of fat mass (FM) unlike fat mass index (FMI). The dual-energy x-ray absorptiometry (DXA) is the gold standard for the determination of FM. A higher percentage of fat mass is associated with metabolic alterations. The Relative Fat Mass (RFM) is a new method to calculate the percentage of FM in a practical way. The aim of this study is to comparatively analyze RFM and FM from DXA as a predictors of the percentage of fat mass, in Mexican adults.


Using the prospectively fed database of the ABC Medical Center, an observational study was conducted in 1747 Mexican adults between 18 and 59 years old, who were evaluated between March 2015 to February 2019. FM percentage was obtained by DXA and anthropometric measurements were taken in the standard way. Linear regression was used for comparison between RFM, DXA, FMI and BMI.


Mean age was 40±10 years, 55% were women. Correlation of the total group, women and men respectively were as follows: between RFM and DXA R2= 0.58 (0.40; 0.51) (p <0.001); between BMI and RFM, R2=0.20 (0.72;0.79) (p <0.001); but FMI DXA vs FMI RFM R2= 0.87 (0.88;0.88) (p <0.001).


RFM is not a good predictor of FM percentage in Mexican adults in comparison to DXA, but it has a significant correlation when it is used to determine FMI.