Search

Introduction: The aim of the study was to evaluate whether subject positioning would affect the measurement of raw body volume, thoracic gas volume, corrected body volume and the resulting percent body fat as assessed by air displacement plethysmography (ADP). Methods: Twenty-five young adult men (20.7±1.1y, BMI = 22.5±1.4 kg/m²) were measured using the BOD PODH system using a measured thoracic gas volume sitting in a 'forward bent' position and sitting up in a straight position in random order. Results: Raw body volume was 58±124 ml (p<0.05) higher in the 'straight' position compared to the 'bent' position. The mean difference in measured thoracic gas volume (bent-straight =271±211 ml) was not statistically significant. Corrected body volume and percent body fat in the bent position consequently were on average 86±122 ml (p<0.05) and 0.5±0.7% (p<0.05) lower than in the straight position respectively. Conclusion: Although the differences reached statistical significance, absolute differences are rather small. Subject positioning should be viewed as a factor that may contribute to between-test variability and hence contribute to (in)precision in detecting small individual changes in body composition, rather than a potential source of systematic bias. It therefore may be advisable to pay attention to standardizing subject positioning when tracking small changes in PF are of interest.The cause of the differences is shown not to be related to changes in the volume of isothermal air in the lungs. It is hypothesized and calculated that the observed direction and magnitude of these differences may arise from the surface area artifact which does not take into account that a subject in the bent position exposes more skin to the air in the device therefore potentially creating a larger underestimation of the actual body volume due to the isothermal effect of air close to the skin. [ABSTRACT FROM AUTHOR]

Abstract: Objective: Evidence of a genetic basis of metabolic risk factors (MRFs) is growing. Studies examining the genetic and environmental basis of the clustering of MRFs, grouped together in the metabolic syndrome (MetS), are however sparse. The aim of this study therefore was to study the heritabilities of the MRFs and the genetic and environmental correlations between the MRFs. Methods: Study participants were 768 Caucasian twins coming from 418 pairs (18–34 years). MRFs were those included in the National Cholesterol Education Program Adult Treatment Panel III definition of the MetS. Multivariate path analysis on the continuous MRFs of the MetS was implemented. Results: Heritabilities ranged between 47.0% and 80.2% (men) and 58.5% and 77.9% (women) for the individual MRFs. Evidence was found for overarching genetic (A) and environmental (E) sources of variance, both however loading mainly on waist circumference. Furthermore, the model included a ‘lipids’ and a ‘blood pressure’-factor both in part attributable to A and E. The majority of the variance however was MRF-specific. Conclusion: Based on our sample of young adults with a low prevalence of the MetS, it can be concluded that both genes and environment contribute significantly to the clustering of the MRFs although the majority of the variation is MRF-specific. Therefore, future QTL searches in young adults may want to focus on MRF-specific loci, rather than ‘cluster-phenotypes’ such as the MetS. [Copyright &y& Elsevier]