P591 - COMPARATIVE ANALYSIS OF BODY COMPOSITION USING THE THREE-COMPARTMENT MODEL: BIOELECTRICAL IMPEDANCE VERSUS STABLE ISOTOPE DILUTION IN HEALTHY JAPANESE ADULTS

P591

COMPARATIVE ANALYSIS OF BODY COMPOSITION USING THE THREE-COMPARTMENT MODEL: BIOELECTRICAL IMPEDANCE VERSUS STABLE ISOTOPE DILUTION IN HEALTHY JAPANESE ADULTS

K. Shiose^1,*, R. T. Tomiga², Y. Higaki²

¹Faculty of Education, University of Miyazaki, Miyazaki, ²Faculty of Sports and Health Science, Fukuoka University, Fukuoka, Japan

Rationale: The three-compartment (3C) model assesses body composition by dividing it into fat mass (FM), total body water (TBW), and residual mass, thereby providing a comprehensive understanding of the body’s condition. TBW is typically measured using the stable isotope dilution method (IDM) in the 3C model but can be more easily estimated using bioelectrical impedance analysis (BIA); therefore, in this study, we compared body composition estimates obtained using IDM and BIA.

Methods: Fifty-seven healthy Japanese men (age: 21±2 year; body mass index: 21.5±2.2 kg/m²) participated in this study. Body density was determined using densitometry. TBW was measured using both IDM and BIA, and each value was separately incorporated into Siri’s 3C model equation with body density. Accordingly, fat mass (%FM) and fat-free mass (FFM) were calculated using the TBW obtained from either IDM (%FM_IDM, FFM_IDM) or BIA (%FM_BIA, FFM_BIA). Paired t test, Pearson’s correlation analysis, and Bland–Altman analysis were used to evaluate the relationships and differences between the body composition values.

Results: No significant differences were observed between %FM_BIA and %FM_IDM (17.6±4.9% vs. 17.9±4.8%) or between FFM_BIA and FFM_IDM (52.7±5.8 kg vs. 52.4±5.3 kg). %FM_BIA and FFM_BIA were strongly correlated with %FM_IDM and FFM_IDM, respectively (%FM: r=0.88; FFM: r=0.97; all p<0.01). Bland–Altman analysis revealed a mean bias of −0.4% for %FM (95%LOA: −3.9% to 3.2%) and 0.3 kg for FFM (95%LOA: −2.0 to 2.6 kg). A small proportional bias was observed for the FFM_BIA (slope=0.09, p=0.014).

Conclusion: In the 3C body composition analysis, substituting BIA for IDM in TBW measurements yielded %FM and FFM estimates with minimal error. Consequently, BIA offers a practical alternative for implementing the 3C model in body composition assessment.

Disclosure of Interest: None declared