PhA emerged as a modest marker of body composition dynamics in youth, particularly in males and during adolescence (post-PHV), whereas other raw BIA parameters, particularly RI, XcpI, and Cap, showed even greater promise in both sexes and across development stages.
Key Findings
Results
Phase angle (PhA) was positively associated with changes in multiple body composition components in both sexes over one year.
In females, PhA was positively associated with changes in fat-related components, fat-free mass, extracellular water, fluids and solids, osseous minerals, and muscle tissue (β = 0.088–0.150; P ≤ 0.05).
In males, PhA was positively associated with alterations in most body components (β = 0.098–0.300; P ≤ 0.05).
The study included 562 healthy and on-time matured youth (51.6% females) followed over 1 year.
Raw BIA parameters were assessed with a phase-sensitive 50 kHz BIA device.
Results
PhA associations with body composition were stronger during the post-PHV stage in both sexes.
During post-PHV, PhA associations with body composition were observed in both females (β = 0.149–0.297; P ≤ 0.05) and males (β = 0.185–0.352; P ≤ 0.05).
Similar trends to those of males were observed in both sexes during post-PHV.
PHV (peak height velocity) stage was used as a stratification variable to assess maturation-dependent differences.
Body composition was assessed through dual-energy X-ray absorptiometry and related models.
Results
Other series and parallel BIA parameters exhibited higher explanatory power of body composition changes than PhA.
In females, the magnitude of associations for other BIA parameters ranged from β = |0.099| to |0.429| (P ≤ 0.05).
In males, associations ranged from β = |0.106| to |0.706| (P ≤ 0.05).
The magnitude of associations depended on each raw BIA parameter, sex, and PHV stage.
Both series and parallel BIA parameters were examined.
Results
Resistance adjusted to stature (RI) showed the highest associations with body composition changes in the total sample and during pre-PHV.
RI demonstrated the highest associations among all raw BIA parameters for the total sample and in the pre-PHV group.
RI is a resistance-based parameter normalized to stature.
Associations were analyzed using multiple linear regression by sex and PHV stage.
RI was identified as having 'even greater promise in both sexes and across development stages' compared to PhA.
Results
Parallel capacitive reactance adjusted to stature (XcpI) and capacitance (Cap) showed the highest associations during the post-PHV stage in both sexes.
XcpI and Cap both demonstrated the highest associations with body composition changes during the post-PHV stage.
These associations were observed in both sexes during post-PHV.
XcpI and Cap are listed among the raw BIA parameters that 'showed even greater promise' than PhA.
The post-PHV period corresponds to the adolescent stage of development.
Conclusions
PhA was identified as a modest longitudinal marker of body composition dynamics in youth, with greater utility in males and during adolescence.
Despite cross-sectional evidence supporting raw BIA parameters as informative markers, their longitudinal role was previously unclear.
PhA showed stronger associations in males compared to females across body composition components.
PhA performed better as a marker during the post-PHV (adolescence) stage.
The study is described as a 1-year prospective cohort investigation, providing longitudinal rather than cross-sectional evidence.
Rosa G, Francisco R, Silva A, Lukaski H, Sardinha L. (2026). Changes in raw bioelectrical impedance parameters as markers of body composition in youth: A prospective cohort investigation.. Nutrition (Burbank, Los Angeles County, Calif.). https://doi.org/10.1016/j.nut.2025.113089