Title of article:

Phenotyping obese subjects: multi-contact electrode bioimpedance system for practical body composition measurement.

Authors: Pietrobelli A, Miller S, Tan YX, Nuñez C, Heymsfield SB.
Poster presented at: Experimental Biology 1999.

Abstract

Objective: Phenotyping for genetic studies of human obesity is important and fatness is a key measurable characteristic. While fatness can be accurately measured using several methods in normal weight or overweight subjects, technical difficulties often arise in moderately or severely obese subjects. The present report describes a new BIA system developed specifically for evaluating total body fat and fat-free body mass (FFM) in subjects with BMI>=30 kg/m2.
Design: Standing obese subjects grip heavy-duty mounted steel electroeds while the plantar surface of their feet maintain electroce contact. The 8-electrode system allows injection of a 50kHz AC current across whole body and then detects corresponding tissue-induced impedance (Z) change.
Results: The system was calibrated by developing a prediction formula with FFM (kg) as dependent and Ht2/Z and age as independent variables in 55 adults with BMI's 18 to 36 kg/m2. FFM was estimated from Siri-3 compartment method based on underwater weighing and 3H2O dilution. The resulting prediction model was: FFM (kg) = 0.51 x Ht2/Z - 0.19 x Age + 15. R2=95; p<001; SEE=3.2 kg (figure). These observations demonstrate the phenotyping potential of a multi-electrode BIA system designed for obese subjects.

fat free mass

Comments and Key points

It has been suspected that leg-to-leg impedance measurements might not be very accurate in very obese people. So this article used a more sophisicated 8-electrode machine, and found no problems in obese people.

 

References

  1. http://www.tanita.com/professional/abstracts/abstract_main.html

Review & comments by Steven B. Halls, MD, Last edited 26-May-2008 Copyright.

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