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 R 2 , 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.