Comparison of clinical body composition methods in people taking weight-inducing atypical antipsychotic medications
Asia Pac J Clin Nutr 2008;17 (4):573-579 573
Jenny-Kay Sharpe PhD1,2 , Nuala M Byrne PhD2, Terry J Stedman FRANZCP1, Andrew P Hills PhD2
1The Park – Centre for Mental Health, Treatment, Education, Research, Queensland, Australia 2Institute of Health and Biomedical Innovation, ATN Centre for Metabolic Fitness, Queensland University of Technology, Queensland, Australia.
The purpose of this study was to compare the accuracy of clinical methods to estimate body fat (%BF) in people who take weight-inducing atypical antipsychotic medications. Forty-seven people (35 males, 12 females) with previously diagnosed psychotic illness who had been taking atypical antipsychotic medications for more than 6 months took part in this study. Percentage body fat was estimated using bioelectrical impedance analysis (BIA) and anthropometry from previously published prediction equations and compared with that measured using the deuterium dilution technique which served as the criterion measure. Bland-Altman analyses were used to assess the agreement between measures. In the males, %BF determined using BIA with the Lukaski equation was the only clinical method with mean differences that were not significant from criterion values. While in the females, %BF determined from BMI was the only method that was significantly different from the criterion values. All of the methods of estimating %BF except Watson equations provided consistent estimates across the weight range. Therefore, this study suggests that in a group of people who predominantly had schizophrenia and were taking atypical antipsychotic medications, BIA using the equation of Lukaski was the best indicator of %BF, although on an individual basis the accuracy was poor. BMI underestimated %BF to a greater significant extent than BIA.
The use of BIA rather than BMI may provide a better indicator of adiposity in people who take weight inducing antipsychotic medications.
Bioelectric Impedance Analysis
Body composition was also estimated using an Imp DF50 (Impedimed, Australia) single frequency bioelectrical impedance analyser to determine resistance and reactance at 50 Hz. Standard operating conditions were observed by a trained operator including preparation of the participant, electrode placement and operation of the Imp DF50 bioelectric impedance analyser.28 The measurement using BIA was taken immediately prior to deuterium dosing with participants lying supine, in a rested state. The equations published by Lukaski et al29 and more recently by Sun et al 30 were also used to estimated percentage body fat from the resistance and reactance values recorded by the Imp DF50. The estimate of %BF made using the Lukaski equation is referred to as %BF (LUK) while the estimate of %BF made using the Sun equation is referred to as %BF (SUN).