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Validity of Body Mass Index as a Measure of Adiposity in Infancy.

ABSTRACT: OBJECTIVES:To assess the validity of body mass index (BMI) and age- and sex-standardized BMI z-score (BMIZ) as surrogates for adiposity (body fat percentage [BF%], fat mass, and fat mass index [kg/m2]) at 3 time points in infancy (1, 4, and 7 months) and to assess the extent to which the change in BMIZ represents change in adiposity. STUDY DESIGN:We performed a secondary analysis of 447 full-term infants in a previous trial of maternal vitamin D supplementation during lactation. Study staff measured infant anthropometrics and assessed body composition with dual-energy x-ray absorptiometry at 1, 4, and 7 months of age. We calculated Spearman correlations (rs) among BMI, BMIZ, and adiposity at each time point, and between change in BMIZ and change in adiposity between time points. RESULTS:Infants (N?=?447) were 52% male, 38% white, 31% black, and 29% Hispanic. The BMIZ was moderately correlated with BF% (rs?=?0.43, 0.55, 0.48 at 1, 4, and 7 months of age, respectively). BMIZ correlated more strongly with fat mass and fat mass index, particularly at 4 and 7 months of age (fat mass rs?=?0.72-0.76; fat mass index rs?=?0.75-0.79). Changes in BMIZ were moderately correlated with adiposity changes from 1 to 4 months of age (rs?=?0.44 with BF% change; rs?=?0.53 with fat mass change), but only weakly correlated from 4 to 7 months of age (rs?=?0.21 with BF% change; rs?=?0.27 with fat mass change). CONCLUSIONS:BMIZ is moderately correlated with adiposity in infancy. Changes in BMIZ are a poor indicator of adiposity changes in later infancy. BMI and BMIZ are limited as surrogates for adiposity and especially adiposity changes in infancy. TRIAL REGISTRATION:ClinicalTrials.gov: NCT00412074.

SUBMITTER: Bell KA

PROVIDER: S-EPMC5924641 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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Validity of Body Mass Index as a Measure of Adiposity in Infancy.

Bell Katherine A KA Wagner Carol L CL Perng Wei W Feldman Henry A HA Shypailo Roman J RJ Belfort Mandy B MB

The Journal of pediatrics 20180315

<h4>Objectives</h4>To assess the validity of body mass index (BMI) and age- and sex-standardized BMI z-score (BMIZ) as surrogates for adiposity (body fat percentage [BF%], fat mass, and fat mass index [kg/m<sup>2</sup>]) at 3 time points in infancy (1, 4, and 7 months) and to assess the extent to which the change in BMIZ represents change in adiposity.<h4>Study design</h4>We performed a secondary analysis of 447 full-term infants in a previous trial of maternal vitamin D supplementation during l ...[more]

PMID: 29551311

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Project description:ObjectiveThe worldwide prevalence of obesity mandates a widely accessible tool to categorize adiposity that can best predict associated health risks. The body adiposity index (BAI) was designed as a single equation to predict body adiposity in pooled analysis of both genders. We compared body adiposity index (BAI), body mass index (BMI), and other anthropometric measures, including percent body fat (PBF), in their correlations with cardiometabolic risk factors. We also compared BAI with BMI to determine which index is a better predictor of PBF.MethodsThe cohort consisted of 698 Mexican Americans. We calculated correlations of BAI, BMI, and other anthropometric measurements (PBF measured by dual energy X-ray absorptiometry, waist and hip circumference, height, weight) with glucose homeostasis indices (including insulin sensitivity and insulin clearance from euglycemic clamp), lipid parameters, cardiovascular traits (including carotid intima-media thickness), and biomarkers (C-reactive protein, plasminogen activator inhibitor-1 and adiponectin). Correlations between each anthropometric measure and cardiometabolic trait were compared in both sex-pooled and sex-stratified groups.ResultsBMI was associated with all but two measured traits (carotid intima-media thickness and fasting glucose in men), while BAI lacked association with several variables. BAI did not outperform BMI in its associations with any cardiometabolic trait. BAI was correlated more strongly than BMI with PBF in sex-pooled analyses (r?=?0.78 versus r?=?0.51), but not in sex-stratified analyses (men, r?=?0.63 versus r?=?0.79; women, r?=?0.69 versus r?=?0.77). Additionally, PBF showed fewer correlations with cardiometabolic risk factors than BMI. Weight was more strongly correlated than hip with many of the cardiometabolic risk factors examined.ConclusionsBAI is inferior to the widely used BMI as a correlate of the cardiometabolic risk factors studied. Additionally, BMI's relationship with total adiposity may not be the sole determinate of its association with cardiometabolic risk.

Project description:BackgroundA single measure that distills complex body mass index (BMI) trajectories into one value could facilitate otherwise complicated analyses. This study creates and assesses the validity of such a measure: average excess BMI.MethodsWe use data from Waves I-IV of the National Longitudinal Study of Adolescent to Adult Health (n = 17,669). We calculate average excess BMI by integrating to find the area above a healthy BMI trajectory and below each subject-specific trajectory and divide this value by total study time. To assess validity and utility, we (1) evaluate relationships between average excess BMI from adolescence to adulthood and adult chronic conditions, (2) compare associations and fit to models using subject-specific BMI trajectory parameter estimates as predictors, and (3) compare associations to models using BMI trajectory parameter estimates as outcomes.ResultsAverage excess BMI from adolescence to adulthood is associated with increased odds of hypertension (OR = 1.56; 95% CI: 1.47, 1.67), hyperlipidemia (OR = 1.36; 95% CI: 1.26, 1.47), and diabetes (OR = 1.57; 95% CI: 1.47, 1.67). The odds associated with average excess BMI are higher than the odds associated with the BMI intercept, linear, or quadratic slope. Correlations between observed and predicted health outcomes are slightly lower for some models using average excess BMI as the focal predictor compared to those using BMI intercept, linear, and quadratic slope. When using trajectory parameters as outcomes, some co-variates associate with the intercept, linear, and quadratic slope in contradicting directions.ConclusionsThis study supports the utility of average excess BMI as an outcome. The higher an individual's average excess BMI from adolescence to adulthood, the greater their odds of chronic conditions. Future studies investigating longitudinal BMI as an outcome should consider using average excess BMI, whereas studies that conceptualize longitudinal BMI as the predictor should continue using traditional latent growth methods.

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Validity of Body Mass Index as a Measure of Adiposity in Infancy.

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Validity of Body Mass Index as a Measure of Adiposity in Infancy.

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