ESPE Abstracts

Background: Determining fat mass (FM) using methods of body composition analysis is useful in diagnosis and treatment of obese adolescents who undergo life style intervention. The use of dual-energy X-ray absorption (DXA) is time-consuming, potentially harmful and expensive. Alternative methods for accurately estimating FM are needed.

Objective and hypotheses: We evaluated single-frequency arm-to-leg bioelectrical impedance analysis at 50 kHz (sf-BIA) in combination with anthropometry for estimating FM in obese adolescents.

Method: 251 obese adolescents (102 males, aged 11.1–19.9 years and 142 females aged, 9.0–25.8 years) were recruited. Height, weight, sf-BIA resistance (R) und reactance (Xc) were measured. FM was measured by DXA. Using linear regression analysis equations for FM were separately determined for both sexes.

Results: Using BIA and anthropometry for estimation of FM we found an acceptable correlation to FM measured by DXA. Linear regression analysis provides the following equations:

FM (kg)=−347.7×ht (cm)+712.1×wt (kg)−63.20×R (Ω)−196.1×Xc (Ω)+11 127 (male; r² =0.87) and FM (kg)=−158.2×ht (cm)+695.1×wt (kg)+27.86×R (Ω)−7745 (female; r² =0.96).

The differences between individual estimated and measured FM ranged from −7.7 to +7.9 kg in male adolescents and from − 4.8 to +4.8 kg in female adolescents. The influence of R and Xc in both equations was low.

Conclusion: Single-frequency BIA analysis is not adequate to accurately estimate FM in obese adolescents. It may have a value for longitudinal monitoring.