Reliability and validity of bioelectrical impedance in determining body composition

Area of Science:

• Exercise Physiology
• Body Composition Analysis
• Anthropometry

Background:

• Accurate body composition measurement is crucial for health and performance assessment.
• Standard anthropometric methods and newer bioelectrical impedance analysis (BIA) are commonly used.
• Understanding the reliability and validity of BIA compared to established methods is essential.

Purpose of the Study:

• To evaluate the reliability and validity of bioelectrical impedance analysis (BIA) for body composition.
• To compare the accuracy of BIA with standard anthropometric methods (skinfold and hydrostatic).
• To assess BIA's correlation with body mass index (BMI).

Main Methods:

• Bioelectrical impedance analysis (BIA), skinfold measurements, and hydrostatic weighing were performed on 68 men and 120 women.
• Reliability was assessed using Generalizability theory, considering day-to-day and intertester error.
• Cross-validation involved correlating BIA-derived percent fat with hydrostatic measurements and BMI.

Main Results:

• BIA, skinfold, and hydrostatic methods demonstrated high reliability (Rxx = 0.957-0.987).
• BIA's cross-validation correlations (0.71-0.76) were significantly lower than sum of seven skinfolds equations (0.88-0.92).
• BIA accuracy was comparable to BMI (correlations 0.74-0.75), with height and weight explaining most variance.

Conclusions:

• While reliable, BIA is less accurate for body composition than skinfold methods.
• BIA's validity is comparable to BMI, suggesting its utility when more advanced methods are unavailable.
• Height and weight are significant predictors in BIA models for body composition.