Can waist circumference provide a new “third” dimension to BMI when predicting percentage body fat in children? Insights using allometric modelling

Introduction Body mass index (BMI) is often criticized for not being able to distinguish between lean and fat tissue. Waist circumference (WC), adjusted for stature, is proposed as an alternative weight status index, as it is more sensitive to changes in central adiposity. Purpose The purpose of the study is to combine the three dimensions of height, mass, and WC to provide a simple, meaningful, and more accurate index associated with percentage body fat (BF%). Methods We employed a four independent sample design. Sample 1 consisted of 551 children (320 boys) (mean ± SD of age = 7.2 ± 2.0 years), recruited from London, UK. Samples 2, 3, and 4 consisted of 5387 children (2649 boys) aged 7 to 17 years recruited from schools in Portugal. Allometric modelling was used to identify the most effective anthropometric index associated with BF%. The data from samples 2, 3, and 4 were used to confirm and cross‐validate the model derived in sample 1. Results The allometric models from all four samples identified a positive mass exponent and a negative height exponent that was approximately twice that of the mass exponent and a waist circumference exponent that was approximately half the mass exponent. Consequently, the body shape index most strongly associated with BF% was urn:x-wiley:20476302:media:ijpo12491:ijpo12491-math-0001. The urn:x-wiley:20476302:media:ijpo12491:ijpo12491-math-0002 component of the new index can simply be interpreted as a WC “weighting” of the traditional BMI. Conclusions Compared with using BMI and WC in isolation, urn:x-wiley:20476302:media:ijpo12491:ijpo12491-math-0003could provide a more effective and equally noninvasive proxy for BF% in children that can be used in public and community health settings

Scaling children's waist circumference for differences in body size

Objectives Both waist circumference (WC) and body size (height) increase with age throughout childhood. Hence, there is a need to scale WC in children to detect differences in adiposity status (eg, between populations and different age groups), independent of body size/height. Methods Using two culturally different samples, 1 English (10–15.9 years n = 9471) and 2 Colombian (14–15 years, n = 37,948), for WC to be independent of height (HT), a body shape index was obtained using the allometric power law WC = a.HTb. The model was linearized using log-transformation, and multiple regression/ANCOVA to estimate the height exponents for WC controlling for age, sex, and any other categorical/population differences. Results In both samples, the power-law height exponent varied systematically with age. In younger children (age 10–11 years), the exponent was approximately unity, suggesting that pre-pubertal children might be geometrically similar. In older children, the height exponent declined monotonically to 0.5 (ie, HT0.5) in 15+ year-olds, similar to the exponent observed in adults. UK children's height-adjusted WC revealed a “u” shaped curve with age that appeared to reach a minimum at peak-height velocity, different for boys and girls. Comparing the WC of two populations (UK versus Colombian 14–15-year-old children) identified that the gap in WC between the countries narrowed considerably after scaling for height. Conclusions Scaling children's WC for differences in height using allometric modeling reveals new insights into the growth and development of children's WC, findings that might well have been be overlooked if body size/height had been ignored

Prediabetes in Pediatric Recipients of Liver Transplant: Mechanism and Risk Factors

ObjectiveTo investigate the role of calcineurin inhibitor exposure and states of insulin resistance-obesity and adolescence-in prediabetes after pediatric liver transplant via oral glucose tolerance testing, which previously has not been done systematically in these at-risk youths.Study designThis was a cross-sectional study of 81 pediatric recipients of liver transplant. Prediabetes was defined as impaired glucose tolerance (IGT; glucose ≥140 mg/dL at 2 hours) or impaired fasting glucose (IFG, ≥100 mg/dL). Corrected insulin response (CIR) was calculated as measure of insulin secretion, corrected for glucose (CIR30, CIR60, CIR120).ResultsSubjects were aged 8.1-30.0 years and 1.1-24.7 years post-transplant; 44% had prediabetes-27% IGT, 14% IFG, and 3% both. IGT was characterized by insulin hyposecretion, with lower CIR60 and CIR120 in IGT than subjects with normal glucose tolerance. Subjects with tacrolimus trough >6 µg/mL at study visit had lower CIR120 than those with trough ≤6 µg/mL and those off calcineurin-inhibitors. Mean of tacrolimus troughs preceding the study visit, years since transplant, and rejection episodes were not associated significantly with lower CIR. CIR suppression by tacrolimus was most pronounced >6 years from transplant. Overweight/obese subjects and adolescents who retained normal glucose tolerance had greater CIR than those who were IGT.ConclusionIGT after pediatric liver transplant is driven by inadequate insulin secretion. It is quite common but not detectable with fasting laboratory values-the screening recommended by current guidelines. Calcineurin inhibitors suppress insulin secretion in these patients in a dose-dependent manner. Given the recent focus on long-term outcomes and immunosuppression withdrawal in these children, longitudinal studies are warranted to investigate whether IGT is reversible with calcineurin inhibitor minimization

Are participant characteristics from ISCOLE study sites comparable to the rest of their country?

OBJECTIVES: The International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE) provides robust, multi-national information on physical activity, diet and weight status in 9–11-year-old children around the world. The purpose of this analysis was to examine the similarities and differences between participant characteristics from ISCOLE sites and data from nationally representative surveys from ISCOLE countries (Australia, Brazil, Canada, China, Colombia, Finland, Kenya, India, Portugal, South Africa, the United Kingdom and the United States). METHODS: Distributions of characteristics were assessed within each ISCOLE country-level database, and compared with published data from national or regional surveys, where available. Variables of comparison were identified a priori and included body mass index (BMI), physical activity (accelerometer-determined steps per day) and screen time (child-report). RESULTS: Of 12 countries, data on weight status (BMI) were available in 8 countries, data on measured physical activity (steps per day) were available in 5 countries and data on self-reported screen time were available in 9 countries. The five ISCOLE countries that were part of the Health Behaviour in School-aged Children Survey (that is, Canada, Finland, Portugal, the United Kingdom (England) and the United States) also provided comparable data on self-reported physical activity. Available country-specific data often used different measurement tools or cut-points, making direct comparisons difficult. Where possible, ISCOLE data were re-analyzed to match country-level data, but this step limited between-country comparisons. CONCLUSIONS: From the analyses performed, the ISCOLE data do not seem to be systematically biased; however, owing to limitations in data availability, data from ISCOLE should be used with appropriate caution when planning country-level population health interventions. This work highlights the need for harmonized measurement tools around the world while accounting for culturally specific characteristics, and the need for collaboration across study centers and research groups