Bioimpedance study of body composition and phase angle in children, adolescents and adults of the Federal Territory Sirius

Background/Objectives: The collection of regional anthropometric and body composition data is essential for medical and epidemiological research, as it allows for the customization of prevention and treatment strategies based on the specific characteristics of different populations. This study aims to investigate sex- and age-related variations in weight-height indices, body composition, and phase angle among the population of the Russian Federal Territory Sirius using bioelectric impedance analysis data. Subjects/Methods: In a non-clinical, cross-sectional study (2021–2024) conducted during community sports, recreational, and cultural events, 3,258 apparently healthy participants (1,915 males; 1,343 females), aged 4–60 years, were assessed with the InBody 770 (Biospace Co., Ltd., Seoul, Republic of Korea). Centiles were derived using the LMS method (GAMLSS/RefCurv). For ages 5–19 years, WHO BMI-for-age SD (z-score) overlays were used; national percentile overlays were examined descriptively. Results: Height peaked at ~20–21 years and declined thereafter; weight/BMI trajectories showed earlier stabilization in females. Absolute SMM rose into early adulthood and BF increased with age, with clear sex dimorphism, with boys showing greater SMM accrual and girls greater fat accumulation during puberty. Relative SMM (%SMM) inflected earlier in females (~14–15 years) than males (~20 years); PA was higher in males, peaking earlier in females (15–17 years) than males (20–25 years) and declining thereafter. Across adulthood, a gradual lean-to-fat shift was evident in both sexes. Two prespecified contrasts illustrated the magnitude of effects: adolescents — %SMM higher in males by 6.10 percentage points (95% CI 5.46–6.74; p < 0.0001); young adults — PA higher in males by 1.20° (95% CI 1.09–1.31; p < 0.0001). Conclusions: The first regional centiles for anthropometry, BIA-derived body composition, and phase angle (PA) in the Federal Territory Sirius show earlier %SMM inflection in females, higher PA in males with an age-dependent decline, and an adult lean-to-fat shift in both sexes. These references support screening, counseling, and age- and sex-specific program design in clinical care, public-health surveillance, and sports science; they also enable electronic health record (EHR)–integrated decision support (regional z-scores and alerts), provide benchmarks for cross-device BIA calibration, and inform AI/ML applications (personalized normative modeling and domain-adapted risk prediction).