The determinants of phase angle differ between adults and children. In adults, the influence of BMI on phase angle depended on the BMI range. The prognostic value of phase angle may differ in different clinical settings. The use of population-specific and probably impedance-analyzer-specific reference values for phase angle is recommended.

Background: The specific resting metabolic rates (K i ; in kcal Á kg 21 Á d 21) of major organs and tissues in adults were suggested by Elia (in Energy metabolism: tissue determinants and cellular corollaries. New York, NY: Raven Press, 1992) to be as follows: 200 for liver, 240 for brain, 440 for heart and kidneys, 13 for skeletal muscle, 4.5 for adipose tissue, and 12 for residual organs and tissues. However, Elia's K i values have never been fully evaluated. Objectives: The objectives of the present study were to evaluate the applicability of Elia's K i values across adulthood and to explore the potential influence of age on the K i values. Design: A new approach was developed to evaluate the K i values of major organs and tissues on the basis of a mechanistic model: REE = R(K i · T i ), where REE is whole-body resting energy expenditure measured by indirect calorimetry, and T i is the mass of individual organs and tissues measured by magnetic resonance imaging. With measured REE and T i , marginal 95% CIs for K i values were calculated by stepwise univariate regression analysis. An existing database of nonobese, healthy adults [n = 131; body mass index (in kg/m 2 ),30] was divided into 3 age groups: 21-30 y (young, n = 43), 31-50 y (middle-age, n = 51), and .50 y (n = 37). Results: Elia's K i values were within the range of 95% CIs in the young and middle-age groups. However, Elia's K i values were outside the right boundaries of 95% CIs in the .50-y group, which indicated that Elia's study overestimated K i values by 3% in this group. Ageadjusted K i values for adults aged .50 y were 194 for liver, 233 for brain, 426 for heart and kidneys, 12.6 for skeletal muscle, 4.4 for adipose tissue, and 11.6 for residuals. Conclusion: The general applicability of Elia's K i values was validated across adulthood, although age adjustment is appropriate for specific applications.

Background: Voluntary sleep restriction is a lifestyle feature of modern societies that may contribute to obesity and diabetes. The aim of the study was to investigate the impact of partial sleep deprivation on the regulation of energy balance and insulin sensitivity. Subjects and Methods: In a controlled intervention, 14 healthy women (age 23–38 years, BMI 20.0–36.6 kg/m²) were investigated after 2 nights of >8 h sleep/night (T0), after 4 nights of consecutively increasing sleep curtailment (7 h sleep/ night, 6 h sleep/night, 6 h sleep/night and 4 h sleep/night; T1) and after 2 nights of sleep recovery (>8 h sleep/night; T2). Resting and total energy expenditure (REE, TEE), glucose-induced thermogenesis (GIT), physical activity, energy intake, glucose tolerance and endocrine parameters were assessed. Results: After a decrease in sleep du-ration, energy intake (+20%), body weight (+0.4 kg), leptin / fat mass (+29%), free triiodothyronine (+19%), free thyroxine (+10%) and GIT (+34%) significantly increased (all p < 0.05). Mean REE, physical activity, TEE, oral glucose tolerance, and ghrelin levels remained unchanged at T1. The effect of sleep loss on GIT, fT3 and fT4 levels was inversely related to fat mass. Conclusion: Short-term sleep deprivation increased energy intake and led to a net weight gain in women. The effect of sleep restriction on energy expenditure needs to be specifically addressed in future studies using reference methods for total energy expenditure.

An eight-electrode, segmental multifrequency BIA is a valid tool to estimate body composition in healthy euvolemic adults compared with the validity and precision of other two-compartment reference methods. Population specificity is of minor importance when compared with discrepancies between different reference methods.

Following experts' consensus, waist circumference (WC) is the best anthropometric obesity index. However, different anatomic sites are used, and currently there is no universally accepted protocol for measurement of WC. In this study, we compare the associations between WC measured at different sites with total visceral adipose tissue (VAT) volume and cardiometabolic risk. Cross-sectional data were obtained from 294 adults and 234 children and adolescents. In addition, longitudinal data were provided in 75 overweight adults before and after dietary-induced weight loss. WC was measured below the lowest rib (WC(rib)), above the iliac crest (WC(iliac crest)), and midway between both sites (WC(middle)). Volumes of VAT and abdominal subcutaneous adipose tissue (SAT) were obtained using MRI. Cardiometabolic risk included blood pressure, plasma lipids, glucose, and homeostasis model (HOMA index). WC differed according to measurement site as WC(rib) < WC(middle) < WC(iliac crest) (P < 0.001) in children and women, and WC(rib) < WC(middle), WC(iliac crest) (P < 0.001) in men. Elevated WC differed by 10-20% in females and 6-10% in males, dependent on measurement site. In men and children, all WC had similar relations with VAT, SAT, and cardiometabolic risk factors. In women, WC(rib) correlated with weight loss-induced decreases in VAT (r = 0.35; P < 0.05). By contrast, WC(iliac crest) had the lowest associations with VAT and cardiometabolic risk factors in women. Each WC had a stronger correlation with SAT than with VAT, suggesting that WC is predominantly an index of abdominal subcutaneous fat. There is need for a unified measurement protocol.