Phase Angle Reference Values Measured Using InBody770 in Japanese Individuals With Normal Fluid Balance

Introduction This survey aimed to present reference values for phase angle (PhA) measured using the InBody770 (InBody Japan Inc., Koto City, Tokyo, Japan) in Japanese individuals with normal fluid balance, defined as an extracellular water/total body water (ECW/TBW) ratio <0.4. Materials and methods This retrospective survey analyzed data obtained from 15,999 measurements of Japanese individuals aged eight to 99 years who were assessed using the InBody770 body composition analyzer. Exclusion criteria were unsuccessful InBody measurements due to impedance errors, individuals with multiple measurement records, aged <10 years, those with a body mass index (BMI) ≥40.0 kg/m², and those with an ECW/TBW ratio ≥0.4. The survey included age, sex, height, weight, BMI, skeletal muscle index (SMI), ECW/TBW, and whole-body PhA. Results After applying the exclusion criteria, the final analysis included 2,562 datasets (959 men and 1,603 women). PhA reference values stratified by age, sex, and BMI using the InBody770 were established. PhA generally decreased with advancing age and tended to be higher in individuals with higher BMI and in men. The overall mean PhA was 5.4 ± 0.8° in men and 4.7 ± 0.5° in women. Conclusions The PhA reference values established in this survey using the InBody770 may serve as a basis for advancing research on PhA and for calculating standardized PhA (SPA) values in Asian populations.