Hispanic Adults Demonstrate Lower Fat-free Mass Density Compared To Cadaver Reference Values: A 4-Compartment Model Approach

Hispanics represent the fastest-growing population in the United States, however an understanding of their body composition profiles remains limited, particularly regarding fat-free mass (FFM) characteristics such as density (DFFM), hydration (TBW:FFM), bone mineral (Mo:FFM), and residual mass (R:FFM). Many stand-alone body fat assessment methods rely on assumed constants derived from Caucasian cadaver reference values, potentially compromising measurement accuracy in Hispanic populations. PURPOSE: This study aimed to quantify FFM characteristics in Hispanic adults, compared against cadaver reference values, using a four-compartment (4C) model. METHODS: One-hundred and thirty participants (60 men and 70 women; aged = 28 ± 12 years, 30 ± 11 years; BMI = 28.28 ± 5.20 kg/m2, 27.90 ± 6.32 kg/m2) were assessed for FFM using deuterium oxide (D2O) for total body water, dual energy x-ray absorptiometry (DXA) for bone mineral content, and air displacement plethysmography (ADP) for body density. Differences between the Hispanic cohort and cadaver reference values were compared using one-sample T-tests, and between group differences were analyzed using independent samples T-tests. RESULTS: Large practical differences in DFFM were observed in Hispanic males (1.093 ± 0.007 g/cm3, ES = 0.97) and females (1.093 ± 0.007 g/cm3, ES = 0.92) when compared to the criterion cadaver reference value (1.100 g/cm3). Despite the large differences in DFFM, the discrepancies in TBW:FFM, Mo:FFM, and R:FFM between Hispanic females and cadaver references were considered trivial to small (ES = 0.17-0.22), whereas for males, the differences in TBW:FFM (mean diff = -0.84%), Mo:FFM (mean diff = -0.47%), and R:FFM (mean diff = 1.31%) ranged from small to large (ES = 0.41-0.97). Comparisons between Hispanic males and females revealed trivial-to-moderate differences in FFM characteristics. CONCLUSIONS: These results indicate that body density and hydration-based assessments in Hispanic adults may be negatively impacted by using assumed constants derived from cadaver reference values. Therefore, clinicians using bioimpedance and body density models to evaluate adiposity in Hispanic adults may risk inaccurate measurements and misclassification of obesity, potentially leading to improper assessment of metabolic health. Supported by: SC1GM135099