Body fat estimations by electrical impedance and infra-red interactance

Area of Science:

• Physiology
• Anthropometry
• Biomedical Engineering

Background:

• Accurate body fat estimation is crucial for health assessment and epidemiological research.
• Hydrodensitometry (underwater weighing) is a criterion method but impractical for field studies.
• Electrical impedance and infra-red interactance offer potentially more accessible alternatives.

Purpose of the Study:

• To evaluate the validity of three electrical impedance devices and one infra-red device for body fat estimation.
• To compare these methods against hydrodensitometry as the criterion standard.
• To determine the suitability of these methods for epidemiological fieldwork.

Main Methods:

• Comparison of three electrical impedance analyzers (RJL Systems, Berkeley Medical Research, Spacelabs) and one infra-red analyzer (Futrex 5000).
• Hydrodensitometry was used as the criterion method for validation.
• Five distinct population groups were assessed, including obese women, athletic adults, slightly obese individuals, normal women, and normal children.

Main Results:

• All tested methods demonstrated highly significant correlations with hydrodensitometry.
• Individual electrical methods showed varying percentage differences from hydrodensitometry across groups (ranging from 1.1% to 56.0%).
• Significant mean differences between an impedance method and hydrodensitometry were found in only two of the tested groups.

Conclusions:

• Electrical impedance methods (excluding one specific device) appear to be reasonably valid alternatives to hydrodensitometry for body fat assessment.
• These methods are particularly suitable for large-scale epidemiological studies due to their practicality.
• Limitations of hydrodensitometry itself should be considered when interpreting results.