Development and validation of new anthropometric equations to estimate fat mass in young adult men and women.

BACKGROUND AND AIM: Anthropometric equations are widely used to estimate fat mass (FM). This study aimed firstly to develop and validate new anthropometric equations for estimating FM using dual-energy X-ray absorptiometry (DXA) as reference method in apparently healthy young adults. Then, we aimed to compare their accuracy with previously published two-component-based models. METHODS AND RESULTS: Five hundred fifteen adults (60% men, 40% women; age 24.2 ± 6.0 years, range 18-45; BMI 23.6 ± 3.1 kg m-2, range 16.2-36.0) underwent standardized anthropometric assessment according to International Society for the Advancement of Kinanthropometry (ISAK) guidelines, including measurement of eight skinfolds, and whole-body DXA. Participants were randomly divided into a development sample (n = 344) and an independent validation sample (n = 171). Two multiple-regression models were developed: a comprehensive equation based on all eight skinfolds and a simplified equation based on a four-skinfold protocol. Model performance was evaluated using R2, standard error of estimate (SEE), mean absolute error (MAE), root mean square error (RMSE), and Bland-Altman analysis. In validation, the 8-skinfold and 4-skinfold equations explained 82% and 80% of the variance in DXA-derived FM, respectively, with low prediction error (MAE 2.23-2.37 kg; RMSE ≤3.03 kg) and no significant bias versus DXA (p > 0.25). In contrast, all previously published equations showed significant bias (p < 0.001), consistently underestimating FM. CONCLUSIONS: DXA-referenced equations derived from standardized ISAK anthropometry demonstrated improved agreement and lower systematic bias compared with traditional two-component-based models.