Body composition in children and Tanner's stages: a study with dual-energy x-ray absorptiometry

Eating behaviors and estimated body fat percentage among adolescents with type 1 diabetes

AIMS

Estimate associations between select eating behaviors and estimated body fat percentage (eBFP) and explore effect modification by sex among adolescents with type 1 diabetes (T1D).

METHODS

This analysis included 257 adolescents (mean age 14.9 ± 1.14 years; 49.8 % female) with baseline hemoglobin A1c (HbA1c) between 8 and 13 % (64 mmol/mol-119 mmol/mol) from a randomized trial designed to improve glycemia. Eating behaviors and eBFP were determined from surveys and validated equations respectively. Linear mixed models were used to estimate associations. Effect modification was assessed via stratified plots, stratified associations, and interaction terms.

RESULTS

Disordered eating, dietary restraint, and eBFP were significantly higher among females while external eating was higher among males. Disordered eating (β: 0.49, 95 %CI: 0.24, 0.73, p = 0.0001) and restraint (β: 1.11, 95 %CI: 0.29, 1.92, p = 0.0081) were positively associated with eBFP while external eating was not (β: -0.19, 95 %CI: -0.470, 0.096, p = 0.20). Interactions with sex were not significant (p-value range: 0.28-0.64).

CONCLUSION

Disordered eating and dietary restraint were positively associated with eBFP, highlighting the potential salience of these eating behaviors to cardiometabolic risk for both female and male adolescents. Prospective studies should investigate whether these eating behaviors predict eBFP longitudinally to inform obesity prevention strategies in T1D.

Sex-Specific Changes in Physical Risk Factors for Anterior Cruciate Ligament Injury by Chronological Age and Stages of Growth and Maturation From 8 to 18 Years of Age

OBJECTIVE

To critically assess the literature focused on sex-specific trajectories in physical characteristics associated with anterior cruciate ligament (ACL) injury risk by age and maturational stage.

DATA SOURCES

PubMed, CINAHL, Scopus, and SPORTDiscus databases were searched through December 2021.

STUDY SELECTION

Longitudinal and cross-sectional studies of healthy 8- to 18-year-olds, stratified by sex and age or maturation on ≥1 measure of body composition, lower extremity strength, ACL size, joint laxity, knee-joint geometry, lower extremity alignment, balance, or lower extremity biomechanics were included.

DATA EXTRACTION

Extracted data included study design, participant characteristics, maturational metrics, and outcome measures. We used random-effects meta-analyses to examine sex differences in trajectory over time. For each variable, standardized differences in means between sexes were calculated.

DATA SYNTHESIS

The search yielded 216 primary and 22 secondary articles. Less fat-free mass, leg strength, and power and greater general joint laxity were evident in girls by 8 to 10 years of age and Tanner stage I. Sex differences in body composition, strength, power, general joint laxity, and balance were more evident by 11 to 13 years of age and when transitioning from the prepubertal to pubertal stages. Sex differences in ACL size (smaller in girls), anterior knee laxity and tibiofemoral angle (greater in girls), and higher-risk biomechanics (in girls) were observed at later ages and when transitioning from the pubertal to postpubertal stages. Inconsistent study designs and data reporting limited the number of included studies.

CONCLUSIONS

Critical gaps remain in our knowledge and highlight the need to improve our understanding of the relative timing and tempo of ACL risk factor development.

Classifying Pubertal Development Using Child and Parent Report: Comparing the Pubertal Development Scales to Tanner Staging

PURPOSE

This project investigated internal consistency and test-retest reliability of the frequently used Pubertal Development Scale (PDS) and compared parent and child reports with clinician-rated Tanner staging.

METHODS

Using a repository of data collected from 1995 to 2016, 252 participants (aged 7.8-17.7 years) provided self- and parent-reported PDS and received Tanner staging by a certified health care professional within 30 days. Internal consistency and test-retest reliability statistics were evaluated for 56 children across two assessments occurring within 6 months. Comparisons with Tanner staging involved examining concurrent validity and calibration analysis using data from 233 child and 252 parental ratings.

RESULTS

Self- and parent-reported PDS demonstrated good internal consistency, with Cronbach's alpha .91-.96; high test-retest reliability was confirmed with intraclass correlation coefficient .81-.92. The association of Tanner stage with self- and parent-reported PDS was moderate to high; Kendall's Tau ranged from .67 to .76, and intraclass correlation coefficient ranged from .73 to 83. The absolute agreement of Tanner stage with self- and parent-reported PDS was low; Cohen's Kappa ranged from .20 to .37. However, combining pubertal scores into three stages of development (pre/early-, mid-, and late/post-pubertal) improved interrater agreement across measures (κ = .65, 95% confidence interval = .57-.73).

CONCLUSIONS

The present study shows that the PDS is reliable and generally tracks with Tanner staging (for both self and parent report). Low absolute agreement indicates that PDS categories do not map directly to specific Tanner stages, partly because a premature adrenarche is often misinterpreted by parents and pediatricians alike. However, three broad categories showed better agreement and are generally adequate for most applications in child and adolescent research.

Sociodemographic associations of longitudinal adiposity in youth with type 1 diabetes

Excess adiposity is common in youth with type 1 diabetes, yet little is known about the sociodemographic factors that predict longitudinal trajectories of body fat. We analyzed data from 363 females and 379 males with type 1 diabetes over ~9 years of follow-up (mean baseline age 12.8 ± 2.3 years in females, 13.2 ± 2.4 years in males). Estimated body fat percentage (eBFP) was calculated with validated sex- and race/ethnicity-specific equations. Group-based modeling identified three eBFP trajectories for each sex. All female trajectories showed gradual increases, while male trajectories showed gradual decreases (<5% in eBFP) that plateaued around 7 years of diabetes duration. Female trajectories showed differences in baseline eBFP: Group F1 (38.0%), mean eBFP 27.8 ± 3.0%: Group F2 (47.9%), mean eBFP 33.9 ± 3.0%: and Group F3 (14.1%), mean eBFP 41.7 ± 4.1%. Male trajectories also showed differences in baseline eBFP: Group M1 (57.2%), mean eBFP 22.0 ± 3.0%: Group M2 (30.9%), mean eBFP 33.9 ± 3.0%: and Group M3 (12.9%), mean eBFP 36.1 ± 3.7%. In multinomial models, adjusted for clinical factors (eg, insulin regimen, insulin dose, and hemoglobin A1c), females who reported a single-parent household (adjusted odds ratio [aOR] = 3.34, 95% confidence interval [CI]: 1.49, 7.47), parental education of less than a college degree (aOR = 3.79, 95% CI: 1.60, 9.60), and a lack of private health insurance (aOR = 3.74, 95% CI: 1.45, 9.60), and a household income of less than $75 000 per year (aOR = 3.13, 95% CI: 1.27, 7.70) were approximately three to four times more likely to be in the highest eBFP trajectory group relative to the lowest eBFP trajectory group. Males who reported a household income of <$75 000/year were almost twice as likely to be in the Group M3 than the Group M1 in the unadjusted model only (aOR = 1.79, 95% CI: 0.91, 4.01 vs unadjusted OR: 2.48, 95% CI: 1.22, 5.06). Lower socioeconomic status may be associated with excess body fat throughout adolescence in type 1 diabetes, particularly among females.

Bone metabolism markers and vitamin D in adolescent cyclists

This study aimed to describe bone metabolic activity in adolescent competitive cyclists compared to age-matched controls. The main result is that younger subjects present a higher bone turnover than the older ones. Moreover, cyclists under the age of 17 have higher scores on all markers than age-matched controls.

PURPOSE

The purpose of this study was to describe bone metabolic activity in adolescent competitive cyclists compared to age-matched controls.

METHODS

Twenty-two male adolescent cyclists between 14 and 20 years (y) and 20 age-matched controls participated in this study. Serum osteocalcin (OC), aminoterminal propeptide of type I procollagen (PINP), and β-isomerized C-telopeptides (β-CTX) were analyzed by electrochemiluminescence immunoassay (ECLIA); plasma 25 hydroxyvitamin D [25(OH)D] was analyzed by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Analysis of variance revealed no significant differences in bone metabolism markers and vitamin D between cyclists and controls. Cyclists over 17 y had a significantly lower concentration in bone formation and resorption biochemical markers compared to cyclists under 17 y (all P < 0.05). Moreover, controls over 17 y presented lower concentration for PINP (P < 0.05) compared to their peers under 17 y. Comparisons between cyclists and controls under 17 y revealed higher concentrations of OC and PINP (P < 0.05) in cyclists. Group interaction by age was found for OC, PINP, and β-CTX (P < 0.01). Cyclists over 17 y had higher concentrations of [25(OH)D] (P < 0.05) than age-matched controls.

CONCLUSIONS

The present results support the idea that cycling during adolescence may be associated to a decrease in bone turnover that may affect bone health later in life.

Weight gain in Turner Syndrome: association to puberty induction? - longitudinal analysis of KIGS data

CONTEXT

Girls with Turner Syndrome (TS) treated or not treated with growth hormone (GH) are prone to overweight. Therefore, we hypothesize that puberty induction in TS is associated with weight gain.

METHODS

We analyzed weight changes (BMI-SDS) between onset of GH treatment and near adult height (NAH) in 887 girls with TS enrolled in KIGS (Pfizer International Growth Database). Puberty was induced with estrogens in 646 (72·8%) girls with TS.

RESULTS

Weight status did not change significantly between GH treatment start and 1 year later (mean difference -0·02 BMI-SDS), but increased significantly (P < 0·001) until NAH (+0·40 BMI-SDS). The BMI-SDS increased +0·21 until start of puberty (P < 0·001). Girls with spontaneous and induced puberty showed similar BMI-SDS changes. Puberty induction at ≥12 years was associated with a significant (P < 0·001) less increase of BMI-SDS (+0·7 BMI-SDS) between baseline and NAH compared to puberty induction at <12 year (+1·0 BMI-SDS). In multiple linear regression analyses changes of BMI-SDS between baseline and NAH were negatively associated with baseline BMI-SDS (P < 0·001), GH doses (P = 0·015), and age at puberty induction (P < 0·001), positively with years on GH treatment (P = 0·004), while duration and dose of estrogens, its route of administration (transdermal/oral), changes of height-SDS, thyroxin and oxandrolone treatment, and karyotype did not correlate significantly to changes of BMI-SDS in this time period.

CONCLUSIONS

Puberty does not seem to play a major role in weight gain in girls with TS since the majority of the increases in BMI-SDS occurred before puberty. However, late puberty induction seems to decrease the risk of weight gain.

Weight Outcomes of Latino Adults and Children Participating in the Y Living Program, a Family-Focused Lifestyle Intervention, San Antonio, 2012-2013

Introduction

US Latinos have disproportionately higher rates of obesity and physical inactivity than the general US population, putting them at greater risk for chronic disease. This evaluation aimed to examine the impact of the Y Living Program (Y Living), a 12-week family-focused healthy lifestyle program, on the weight status of adult and child (aged ≥7 years) participants.

Methods

In this pretest–posttest evaluation, participants attended twice-weekly group education sessions and engaged in physical activity at least 3 times per week. Primary outcome measures were body mass index ([BMI], zBMI and BMI percentile for children), weight, waist circumference, and percentage body fat. Wilcoxon signed-rank tests and mixed effects models were used to evaluate pretest–posttest differences (ie, absolute change and relative change) for adults and children separately.

Results

BMI, weight, waist circumference, and percentage body fat improved significantly (both absolutely and relatively) among adults who completed the program (n = 180; all P ≤ .001). Conversely, child participants that completed the program (n = 72) showed no improvements. Intervention effects varied across subgroups. Among adults, women and participants who were obese at baseline had larger improvements than did children who were obese at baseline or who were in families that had an annual household income of $15,000 or more.

Conclusion

Significant improvements in weight were observed among adult participants but not children. This family-focused intervention has potential to prevent excess weight gain among high-risk Latino families.

The effect of gonadotrophin-releasing hormone agonist treatment over 3 years on bone mineral density and body composition in girls with central precocious puberty

OBJECTIVE

Puberty is a period characterized by growth spurt and rapid change in body composition. The effect of GnRH agonist therapy for central precocious puberty on bone mineral density is unclear. We demonstrated changes in bone mineral density in subjects with central precocious puberty, who were treated with GnRH agonist for more than 3 years.

DESIGN

The changes in bone mineral density and body compositions were tested with analysis of variance with repeated measures to identify statistical significance over the treatment period.

PATIENTS

One hundred ninety-five Korean girls with central precocious puberty were treated with GnRH agonist, and among these subjects, 39 patients were treated for more than 3 years.

MEASUREMENTS

Dual-energy X-ray absorptiometry was performed on the subjects at the initial evaluation and once yearly thereafter while on the treatment.

RESULTS

The bone mineral density parameters for chronological age tended to decrease near the mean for the treatment period; however, they increased significantly for bone age excluding bone mineral apparent density. An increment of the BMI was not significant for the chronological age.

CONCLUSIONS

Three-year treatment with GnRH agonist in central precocious puberty patients did not impair bone maturation. GnRH agonist could be effectively commenced in girls with precocious puberty from an early age.

Age and sex differences in fat distribution in non-obese Japanese children

OBJECTIVE

To assess fat distribution in non-obese Japanese children and adolescents.

DESIGN

130 non-obese Japanese children (73 boys and 57 girls) from Kikugawa, Hamamatsu were included. The visceral fat area (VFA) and subcutaneous fat area (SFA) were measured by computed tomography (CT) and calculated (in cm(2)). Subjects were divided into three groups based on age: group A (6-10 years), group B (11-15 years), and group C (16-20 years).

RESULTS

Girls had more subcutaneous fat than boys in groups B and C (P<0.01). Boys had an age-dependent increase in visceral fat, but girls did not. In group C (16-20 years), boys had more visceral fat than girls (P<0.01).

CONCLUSIONS

In non-obese Japanese children, there are significant differences in visceral and subcutaneous fat amounts by age and sex. VFA seems to accumulate more in boys than in girls, and SFA is more prevalent in girls than boys.

Changes and tracking of fat mass in pubertal girls

Puberty is a critical period in body composition development. The influence of puberty on the development of fat mass asks for further investigation. We investigated the development of fat mass during puberty in a longitudinal prospective study in 152 healthy nonobese white girls, initial ages between 9 to 12 years. The influence of menarcheal age and the existing of tracking of fat mass have been analyzed. In 10 years time, participants were measured on eight time points. Various anthropometric data were collected, breast development was staged according to Tanner and body composition was determined with the dual-energy X-ray absorptiometry (DXA) scan. Calculations were made with the use of a linear mixed model. Fat mass increases from 7.9 kg (23.6%) at B1 to 18.5 kg (29.3%) at B5. Fat mass is higher in girls with an early menarche than in girls with a late menarche from B2. Girls in the quartile with initially the lowest fat mass have a chance of being in the same quartile after 10 years of 77% (P < 0.001). Girls in the quartile with initially the highest fat mass, have a risk of staying in the highest quartile of 55% (P < 0.001). Menarcheal age is of great influence on the development of fat mass. Girls with an early menarche, will have a bigger fat mass, especially at the end of puberty. Tracking of fat mass exists: a high amount of fat mass in early puberty will continue to exist at young adulthood.

Comparison of changes in body composition during puberty development of obese and normal-weight children in China

OBJECTIVE

To compare the changes in body composition, including fat mass index (FMI) and fat free mass index (FFMI) during puberty development of obese and normal-weight children in China, and to explore the effect of age and gender on body composition.

METHODS

A total of 356 children at the age of 7-15 years were enrolled in this study. Body composition of 10 normal-weight and obese children in each age group was measured by dual-energy x-ray absorptiometry (DEXA). FFMI and FMI were calculated according to the following formula: FFMI (kg x m(-2)) = FFM(kg) / height2 (m2) and FMI (kg x m(-2)) = FM (kg) / height2 (m2).

RESULTS

The fat mass and fat free mass of obese children were significantly higher than those of normal-weight children (P < 0.05). The FMI and FFMI of obese children increased significantly with age and were higher than those of the same sex, gender, and age normal-weight children (P < 0.05).

CONCLUSION

The levels of fat mass, fat free mass, FMI, and FFMI are different in obese and normal-weight children, and gender effects are significant in boys having higher levels of these indicators than in girls. FFMI and FMI can be used as monitoring indexes in weight control of obese children.

The relationship between leptin, gonadotropic hormones, and body composition during puberty in a Dutch children cohort

OBJECTIVE

To investigate the relationship between leptin concentrations, gonadotropic hormone concentrations, and body composition during puberty in a Dutch children cohort.

DESIGN

In a cohort of 98 children, we determined anthropometric measurements, body composition, and concentrations of leptin, FSH, and LH.

RESULTS

Sex differences were observed from Tanner stage 1 onwards in weight, body fat percentage, and leptin/fat mass ratio. In boys and girls, the relationship between leptin concentrations and FM was weaker at Tanner stage 2 (R(2)=0.33 and R(2)=0.39; P<0.001), 3 (R(2)=0.27 and R(2)=0.36; P<0.002), and 4 (R(2)=0.21 and R(2)=0.28; P<0.03) than at Tanner stage 1 (R(2)=0.51 and R(2)=0.67; P<0.001) and 5 (R(2)=0.46 and R(2)=0.78; P<0.01). In girls, a peak in leptin concentrations (8.5+/-6.0 ng/ml) preceded a peak in LH and FSH concentrations (15.1+/-3.5 and 5.0+/-4.5 IU/l). A lead/lag relationship was observed of leptin at Tanner stage 1 to LH and FSH at Tanner stage 2 (R(2)=0.12, P<0.05 and R(2)=0.18, P<0.05). In boys, there was no peak in leptin, LH, and FSH; additionally, leptin at Tanner stage 3 was related FSH at Tanner stage 4 (R(2)=0.17, P<0.04).

CONCLUSION

In boys and girls during puberty, factors independent of fat mass become (transiently) more important in the regulation of plasma leptin concentrations. Moreover, in girls, leptin is suggested to act as a permissive factor for the onset of puberty, while, in boys, leptin has a different timing and possibly different function.

Leptin-adiposity relationship changes, plus behavioral and parental factors, are involved in the development of body weight in a Dutch children cohort

BACKGROUND

The development of body weight is determined by different factors, namely genetic, behavioral, parental and physiological.

OBJECTIVE

To investigate whether genetic, behavioral, parental and physiological factors are involved and the extent of involvement in the development of body weight at ages 12 and 13 y in a Dutch children cohort.

METHODS

In a Dutch cohort of 94 children at ages 12 and 13 y, we determined anthropometric measurements, body composition, leptin concentrations, TFEQ scores, physical activity, as well as 3 polymorphisms, and in the parents we determined anthropometric measurements and TFEQ scores.

RESULTS

11% of the children in the cohort were classified as overweight. The genotype frequency distributions of the PPARy2, GRL and CNTF genes at ages 12 and 13 y were not significantly different for the overweight children compared to the lean children. Overweight children showed higher dietary restraint and disinhibition scores. Overweight children's parents had a higher BMI, dietary restraint and disinhibition scores, compared to lean children's parents. A peak in leptin concentrations between 7 and 13 y was shown at 12 y. In lean boys, the decrease in leptin concentrations between 12 and 13 y was related to an increase in fat free mass. At the age of 12 y predominantly the physiological factors were predictors for body weight, and at the age of 13 y both the physiological and behavioral factors were predictors for body weight.

CONCLUSION

We conclude from this longitudinal study, that leptin appeared to play an important role in the development of body weight during puberty, in addition to behavioral and parental factors.

Pediatric dual-energy X-ray absorptiometry: technique, interpretation, and clinical applications

This article reviews the dual-energy x-ray absorptiometry (DXA) technique, its interpretation, and clinical applications with emphasis on the considerations unique to pediatrics. Specifically, the use of DXA in children requires the radiologist to be a "clinical pathologist," monitoring the technical aspects of the DXA acquisition, a "statistician" knowledgeable in the concepts of Z-scores and least significant changes, and a "bone specialist," aware of the DXA findings in a large number of clinical diseases, providing the referring clinician with a meaningful context for the numeric result obtained with DXA.

An evaluation of patterns of change in total and regional body fat mass in healthy Spanish subjects using dual-energy X-ray absorptiometry (DXA)

BACKGROUND/OBJECTIVE

The aim of this study was to describe the evolution of total and regional fat mass according to gender, and to establish age and gender-related differences in a largely non-obese sedentary Spanish sample population using dual-energy X-ray absorptiometry (DXA).

SUBJECT/METHODS

A total of 1113 healthy subjects (397 male and 716 female) from the city of Alcalá de Henares (Madrid), Spain, were used in the study. Fat mass measures were obtained from DXA scans of all subjects. Total body fat and body fat in three subregions (trunk, arms and legs) were evaluated.

RESULTS

As opposed to males, females showed from early infancy a smaller rate of muscular mass and a larger percentage of body fat (from 10 years of age), with fat deposits being basically gynoid or peripheral. With age, females showed a greater increase in fat mass together with an accelerated loss of muscular mass. Both rates tended to level out between 51 and 65 years of age. Between the ages of 40 and 60, females exhibited significant morphological evidence of larger fat depots in their legs.

CONCLUSIONS

Gender differences in the patterns of proportion and distribution of body fat, as well as in the pattern of body fat evolution, were found from early infancy. Further research is required, including assessing fat mass variables in order to unravel the dynamic of body composition and to understand the complex relationship between trunk fat mass deposits and the health risks associated with obesity.

Stunted children gain less lean body mass and more fat mass than their non-stunted counterparts: a prospective study

The aim of the present study was to analyse the changes in body composition of stunted children during a follow-up period and to test the hypothesis of a tendency to accumulate body fat as a consequence of undernutrition early in life. We selected fifty boys and girls aged 11 to 15, who were residents of slums in São Paulo, Brazil. Twenty were stunted (S) and thirty had normal stature (NS). The children's nutritional status and body composition were assessed through anthropometry and dual-energy X-ray absorptiometry, at the beginning of the present study and after 3 years, and changes in lean mass (LM and LM%) and fat mass (FM and FM%) were calculated. Stunted boys accumulated more body fat (FM%: S=1·62%, NS=−3·40%;P=0·003) and gained less lean mass (LM%: S=−1·46, NS=3·21%;P=0·004). Stunted girls gained less lean mass (S=7·87 kg, NS=11·96 kg;P=0·032) and had significantly higher values of FM% at follow-up when compared with their baseline values (P=0·008), whereas non-stunted girls had a non-significant difference in FM% over time (P=0·386). These findings are important to understand the factors involved in the increased prevalence of overweight and obesity among poor populations, which appear to be associated with hunger during infancy and/or childhood.

Pediatric DXA: technique and interpretation

This article reviews dual X-ray absorptiometry (DXA) technique and interpretation with emphasis on the considerations unique to pediatrics. Specifically, the use of DXA in children requires the radiologist to be a "clinical pathologist" monitoring the technical aspects of the DXA acquisition, a "statistician" knowledgeable in the concepts of Z-scores and least significant changes, and a "bone specialist" providing the referring clinician a meaningful context for the numeric result generated by DXA. The patient factors that most significantly influence bone mineral density are discussed and are reviewed with respect to available normative databases. The effects the growing skeleton has on the DXA result are also presented. Most important, the need for the radiologist to be actively involved in the technical and interpretive aspects of DXA is stressed. Finally, the diagnosis of osteoporosis should not be made on DXA results alone but should take into account other patient factors.

Body mass index and body composition measures by dual x-ray absorptiometry in patients aged 10 to 21 years with spinal cord injury

BACKGROUND/OBJECTIVE

To determine the body composition of adolescents with spinal cord injury (SCI) and to assess whether established cutoff values for obesity determined by body mass index (BMI) are valid for this population.

METHODS

Sixty patients, aged 10-21 years, with traumatic SCI (50 with paraplegia and 10 with tetraplegia) were compared with 60 gender-, age-, and BMI-matched controls (CTRL). Dual-energy x-ray absorptiometry was used to estimate regional and total bone mineral content, lean tissue mass, fat tissue mass, and body fat percentage. BMI was calculated from measured weight and stature (kg/m2).

RESULTS

Total percent body fat was significantly higher in the paraplegia group (31.4% +/- 1.2%; mean +/- SE) than in the tetraplegia and CTRL groups (25.7% +/- 2.7% and 22.9% +/- 1.1%, respectively). This change in percent total body fat was associated with a reduction of lean tissue mass in the paraplegia (37.6 +/- 1.1 kg; mean +/- SE) and tetraplegia (32.8 +/- 2.5 kg) subjects as compared to the CTRL group (46.2 +/- 1.0 kg; P < 0.001). Total fat mass was significantly greater in the paraplegia group (19.3 +/- 1.3 kg) than the CTRL and tetraplegia groups (14.9 +/- 1.2 kg and 11.7 +/- 3.0 kg, respectively). Regional measurements revealed that the greatest reduction of lean tissue mass in the SCI subjects occurred in the lower extremities, followed by the trunk. As a result of these changes in body composition, the optimal BMI for classifying obesity (trunk fat percent >30 in males and >35 in females) in subjects with SCI was 19 kg/m2 as compared to 25 kg/m2 in able-bodied subjects.

CONCLUSIONS

Patients aged 10 to 21 years with SCI have significantly decreased lean tissue mass and bone mineral content, and increased fat mass. As a result, traditional BMI cutoff criteria significantly underestimate obesity in this population. New clinically applicable criteria to define obesity should be established for SCI children and adolescents with SCI.

Normative data for adiponectin, resistin, interleukin 6, and leptin/receptor ratio in a healthy Spanish pediatric population: relationship with sex steroids

OBJECTIVES

To investigate the circulating levels of adiponectin, resistin, interleukin 6 (IL-6), and leptin/receptor ratio in healthy Spanish children throughout the different stages of pubertal development. To analyze the relationship between adipokines and sex steroid level changes during puberty.

STUDY DESIGN

Serum adiponectin, resistin, IL-6 levels, and leptin/receptor ratio were studied in 160 healthy Spanish children grouped according to their pubertal stage (Tanner I, 23 girls and 22 boys; Tanner II, 19 girls and 16 boys; Tanners III and IV, 21 girls and 20 boys; and Tanner V, 20 girls and 19 boys). In addition, circulating levels of sex hormone-binding globulin (SHBG) were determined in every subject, and testosterone and estradiol levels in boys and girls respectively.

RESULTS

Adiponectin levels decreased in boys from mid puberty (P < 0.05) to become significantly lower than in girls (P < 0.001), whereas IL-6 decreased in both sexes (P < 0.05). Resistin levels and leptin/receptor ratio showed no differences between sexes or according to pubertal stage, except in adult females, who had the highest levels of both parameters (P < 0.001). Serum IL-6 levels correlated significantly (P < 0.05) with testosterone and estradiol levels (r=-0.37 and -0.42 respectively), whereas estradiol, but not testosterone, correlated with leptin/receptor ratio (r=0.59; P < 0.001). Furthermore, a positive relationship was found between SHBG and adiponectin and IL-6 (P < 0.001 and P < 0.05 respectively). In addition, a direct correlation between leptin/receptor and body mass index was found in both sexes (P < 0.001).

CONCLUSION

Variations in adipokine profiles throughout pubertal development appear to be related with progression of gonadal function.

Body composition and water compartment measurements in boys with Duchenne muscular dystrophy

OBJECTIVE

Duchenne muscular dystrophy (DMD) patients have a lower percentage of total body water and higher extracellular water to intracellular water (ECW/ICW) ratio compared with normal subjects. However, it is not known whether this is due to increased fat mass or a decreased amount of ICW in muscle cells in DMD patients. The purpose of this study was to (1) determine the effect of increased fat mass and decreased lean mass on the ECW to ICW ratio in DMD patients and to (2) determine the validity of multifrequency bioelectrical impedance analysis (MFBIA) in assessing body composition in DMD patients.

DESIGN

This study has a quasi-experimental, comparative design using nonequivalent groups. A total of 46 boys ranging from 6 to 13 yrs of age participated in this study. There were 12 nonobese able-bodied controls, 19 obese able-bodied children (obese), and 15 boys with DMD. Body composition was measured by dual-energy x-ray absorptiometry (DEXA). Body composition and body water compartment analysis were assessed by MFBIA. All measurements obtained using MFBIA were compared with those obtained using DEXA for validation.

RESULTS

Both MFBIA and DEXA measures were strongly correlated in control (r = 0.99), obese (r = 0.92), and DMD subjects (r = 0.95). However, lean tissue mass measured by DEXA in the DMD subjects was only slightly higher (19.2 +/- 1.1 vs. 18.2 +/- 1.2, P < 0.02) than as measured by MFBIA. Mean percentage of body fat measured by DEXA in the DMD subjects (30.4 +/- 3.1%) was significantly lower than as measured by MFBIA (38.7 +/- 2.2%). The mean percentage of body fat measured by DEXA in the control group (23.2 +/- 1.8%) was significantly (P < 0.001) lower than as measured by MFBIA (28.6 +/- 1.6%). The mean percentage of body fat measured by DEXA in obese able-bodied controls (40.8 +/- 0.9%) was not significantly different from that measured by MFBIA (40.4 +/- 1.5%). Compared with the obese and control subjects, DMD subjects showed reduced ICW and ECW, with an increased ECW/ICW ratio, as expected. However, the percentage of fat for the DMD group was not different from the obese group.

CONCLUSIONS

DMD patients have elevated ECW/ICW ratios compared with obese subjects and nonobese controls. However, obese subjects and nonobese controls had similar ECW/ICW ratios, despite the increased fat tissue mass in obese subjects. This suggests that the elevated ECW/ICW ratios in DMD subjects are not due to increased fat mass but rather some other mechanism, likely impaired cellular homeostasis due to muscle membrane instability. Although MFBIA slightly underestimates lean tissue mass in boys with DMD, it has a potential role as an inexpensive and easy to use measurement tool to measure changes in muscle mass in the clinical setting.

Early sexual maturation, body composition, and obesity in African-American girls

OBJECTIVE

To describe associations between sexual maturation and body composition in a sample of African-American girls who were participants in phase 1 pilot interventions of the Girls Health Enrichment Multisite Studies.

RESEARCH METHODS AND PROCEDURES

Stature, weight, and waist circumference were measured. Pubic hair and breast development were assessed, and body composition was measured by DXA for 147 African-American girls who were 8 to 10 years of age from three field centers. Participants had BMI > or =25th percentile for age (one site) or BMI > or =50th percentile for age.

RESULTS

Girls Health Enrichment Multisite Studies girls had greater BMI, fat mass, and percentage body fat than national norms and relatively earlier initiation of breast development and pubic hair. Increasing stages of breast development, but not stages of pubic hair, were related to increased stature, waist circumference, BMI, lean mass, fat mass, and percentage of body fat. Pubescent girls (breast stage > or = 2) were greater than six times as likely to be classified as at risk of overweight (BMI > or = 85th percentile) and greater than eight times as likely to be classified as overweight (BMI > or = 95th percentile) as prepubescent counterparts. Adjusted odds ratios for advanced breast development [breast stage > or = 2 (8 years) or > or = 3 (9 and 10 years)] were 3.6 for risk of overweight and for overweight compared to girls with average or less than average breast development.

DISCUSSION

Sexual maturation is important to consider in understanding the classification of overweight and the development of obesity during adolescence. Breast development and pubic hair development should be considered separately for their associations with growth and body composition.

Altered body composition affects resting energy expenditure and interpretation of body mass index in children with spinal cord injury

BACKGROUND

Individuals with spinal cord injury (SCI) typically undergo changes in their body composition (reduction in lean body mass and an increase in fat mass) that can lead to secondary complications associated with diminished physical activity and obesity.

METHODS

This study used dual energy X-ray absorptiometry (DXA) to estimate the total lean tissue mass (LTM), total body fat, and total bone mineral content (BMC) to assess the relationship between body mass index (BMI), body composition, and resting metabolic rate (RMR) in a group of children with SCI who were matched with able-bodied controls for age and sex. Body composition and RMR were measured in 18 boys and 9 girls (10-21 years of age) who had a SCI in the previous 1 to 3 years and in 27 age- and sex-matched controls.

RESULTS

Children with SCI had significantly lower mean LTM than control subjects (37.6 +/- 9.6 kg and 46.7 +/- 9.2 kg, respectively; P < 0.001) and higher percent body fat (26.4 +/- 7.9% and 20.2 +/- 8.5%, respectively; P < 0.02) as measured by DXA, despite their reduced BMI (18.9 +/- 3.8 kg/m2 and 21.2 +/- 2.9 kg/m2, respectively; P < 0.01). Children with SCI had lower RMR than the controls subjects (1213 +/- 334 kJ/d and 1511 +/- 257 kJ/d, respectively), but there was no difference in RMR when adjusted for LTM.

CONCLUSION

Children with SCI have lower RMRs that are associated with their reduced LTM. The reduction in LTM and RMR may predispose children with SCI to relative gains in body fat. BMI significantly underestimates body fat in children with SCI.

Plasma leptin is associated with insulin resistance independent of age, body mass index, fat mass, lipids, and pubertal development in nondiabetic adolescents

OBJECTIVE

The rising epidemic worldwide in overweight and obese children requires urgent attention. Leptin has been found to be associated with body weight control and possibly affects insulin sensitivity. Since insulin resistance is associated with obesity in adults and possibly in adolescents, we set out to investigate the association of plasma leptin level with various anthropometric indices, body fat mass (FM), lipids, and insulin resistance (IR) index in nondiabetic adolescents.

DESIGN

A cross-sectional study from three high schools in Taipei City in Taiwan.

SUBJECTS

A total of 402 nondiabetic subjects (162 boys and 240 girls; age range, 10-19 y; mean age, 15.8+/-1.9 y, and mean body mass index (BMI), 24.8+/-4.6 kg/m(2)) were recruited.

MEASUREMENTS

The fasting plasma leptin, plasma glucose, insulin, lipids, and anthropometric indices including height, weight, waist (WC) and hip circumferences, and waist-to-hip ratio (WHR) were examined. Total body FM and percentage body fat (FM%) were obtained from dual-energy X-ray absorptiometry. The homeostasis model was applied to estimate the degree of IR.

RESULTS

The plasma leptin levels were significantly higher in girls (17.45+/-10.13 ng/ml) than boys (8.81+/-6.71 ng/ml, P<0.001). The plasma leptin levels were positively correlated to BMI, WC, WHR, FM, FM%, and triglycerides (TG). The IR index was positively correlated to BMI, WC, WHR, FM, FM%, TG, and leptin. Using the multivariate linear regression models, we found that plasma leptin remains significantly associated with IR index even after adjusting for age, gender, BMI, FM, WC, Tanner stage, and TG.

CONCLUSION

Plasma leptin was associated with IR index independent of age, gender, BMI, FM, WC, Tanner stage, and TG. Plasma leptin levels in adolescents could be a predictor for the development of the metabolic syndrome disorders and cardiovascular diseases.

Sex-related differences between adiponectin and insulin resistance in schoolchildren

OBJECTIVE

To study the effect of body composition and adiponectin on insulin resistance and beta-cell function in schoolchildren during puberty.

RESEARCH DESIGN AND METHODS

Plasma adiponectin level and its relationships with insulin sensitivity and beta-cell function were analyzed in 500 randomly recruited nondiabetic Taiwanese schoolchildren (245 boys and 255 girls) aged 6-18 years in a national survey program for diabetes in 1999. Insulin resistance and beta-cell function were evaluated by homeostasis model assessment (HOMA). Plasma adiponectin concentrations were determined with radioimmunoassay.

RESULTS

Plasma glucose levels remained stable, whereas insulin resistance increased with a compensatory rise in beta-cell function during this period. A transient drop of adiponectin level with a trough at 10-12 years was found in boys but not in girls. This pubertal drop of adiponectin levels in boys coincides with the sharp rise in testosterone concentration. A negative correlation between testosterone levels and adiponectin concentration was also noted in boys (r = -0.142, P = 0.032). Plasma adiponectin levels correlated inversely with relative body weight, fasting insulin concentrations, and insulin resistance index by HOMA in boys aged 15-18 years and in girls aged 11-14 years. No association was observed between adiponectin levels and beta-cell function by HOMA.

CONCLUSIONS

There is a transient drop in the level of adiponectin during male puberty, correlated with the increase in testosterone level in boys. Plasma adiponectin levels were inversely correlated with obesity and insulin resistance in boys and girls during the pubertal period.

Physical activity, health impairments, and disability in neuromuscular disease

Reduced physical activity is a consequence of progressive neuromuscular diseases, which negatively impacts quality of life and health outcomes. Reduced functional muscle mass is common to all neuromuscular diseases and results from both atrophy of disuse secondary to a sedentary lifestyle and muscle degeneration secondary to the disease itself. This review summarizes current concepts relating to the impact of reduced physical activity on health and fitness, potential determinants of physical activity levels in neuromuscular diseases, and new approaches to the quantitative measurement of physical activity in neuromuscular disease populations. The interrelationship of disease pathophysiology, impairment, functional limitation, disability, and societal limitation in the determination of physical activity in the community in neuromuscular diseases is discussed using Duchenne muscular dystrophy as an example. Future research pertaining to physical activity in neuromuscular disease will need to focus on the development of scientifically based recommendations concerning optimal exercise approaches with both disease-specific and general guidelines.

Bone, muscle, and fat: sex-related differences in prepubertal children

PURPOSE

To determine whether there are sex-related differences in vertebral cross-sectional dimensions, in paraspinous muscle area, and in the amount of fat in the subcutaneous and visceral compartments of prepubertal boys and girls.

MATERIALS AND METHODS

Subcutaneous fat, visceral fat, paraspinous musculature, and vertebral cross-sectional dimensions were studied in 31 pairs of prepubertal healthy white girls and boys 5-10 years of age, rigorously matched for age, height, and weight. Data were analyzed with the Student t test and multiple regression analysis.

RESULTS

Sex had a differential effect on fat accumulation and musculoskeletal development. Compared with boys, girls had, on average, 28% greater total fat and 30% higher subcutaneous fat (P <.001 for both), but 10% less paraspinous musculature (P =.002) and 15% smaller vertebral cross-sectional dimensions (P <.001). In contrast, the sexes were monomorphic for visceral fat (P =.24). Stepwise regression analysis indicated that only 22% of the difference in vertebral cross-sectional area could be explained by sex-related differences in paraspinous musculature.

CONCLUSION

Together, these data indicate that sex is an important determinant of the morphology in humans well before the beginning of puberty.

Prepubertal Asians have less limb skeletal muscle

Skeletal muscle mass in prepubertal Asian children has not been examined previously. The aims of this study were to test the hypotheses that 1) prepubertal Asians have less appendicular skeletal muscle (ASM) mass compared with African-Americans and Caucasians, and 2) ASM is less in prepubertal Asian girls compared with Asian boys. ASM was estimated by using dual-energy X-ray absorptiometry in healthy prepubertal girls (n = 170) and boys (n = 166). The results showed that, after adjusting for age, height, and body weight, 1) Asian girls and boys had less amounts of ASM than African-Americans (P < 0.001); 2) Asian girls had less amounts of ASM than Caucasian girls (P = 0.004); 3) there was a trend towards less ASM in Asian compared with Caucasian boys (P = 0.07); 4) and Asian girls had significantly less ASM than Asian boys (P < 0.001). This study indicates that skeletal muscle mass as a fraction of body weight is smaller in Asian compared with African-American and Caucasian children.

Self-reported calcium intake and bone mineral content in children and adolescents

OBJECTIVE

We examined the relationship between self-reported calcium (Ca) intake and bone mineral content (BMC) in children and adolescents. We hypothesized that an expression of Ca adjusted for energy intake (EI), i.e., Ca density, would be a better predictor of BMC than unadjusted Ca because of underreporting of EI.

METHODS

Data were obtained on dietary intakes (repeated 24-hour recalls) and BMC (by DEXA) in a cross-section of 227 children aged 8 to 17 years. Bivariate and multivariate analyses were used to examine the relationship between Ca. Ca density, and the dependent variables total body BMC and lumbar spine BMC. Covariates included were height, weight, bone area. maturity age, activity score and EI.

RESULTS

Reported EI compared to estimated basal metabolic rate suggested underreporting of EI. Total body and lumbar spine BMC were significantly associated with EI, but not Ca or Ca density, in bivariate analyses. After controlling for size and maturity, multiple linear regression analysis revealed unadjusted Ca to be a predictor of BMC in males in the total body (p = 0.08) and lumbar spine (p = 0.01)). Unadjusted Ca was not a predictor of BMC at either site in females. Ca density was not a better predictor of BMC at either site in males or females.

CONCLUSIONS

The relationship observed in male adolescents in this study between Ca intake and BMC is similar to that seen in clinical trials. Ca density did not enable us to see a relationship between Ca intake and BMC in females, which may reflect systematic reporting errors or that diet is not a limiting factor in this group of healthy adolescents.

Pubertal maturation characteristics and the rate of bone mass development longitudinally toward menarche

To assess risks for osteoporosis and to compare bone mass in different groups of healthy children or children with diseases, it is important to have knowledge of their sexual maturation status during puberty. The aim of our study was to evaluate bone mass formation longitudinally in relation to pubertal maturation characteristics in healthy white girls. We investigated the bone mineral content (BMC) and the bone mineral density (BMD) at different skeletal sites in 151 girls with increasing pubertal stages in relation with their chronological age and with an early or late onset of puberty or menarche and with a slow or fast maturation. Bone mass was measured at the onset of puberty, during puberty, and at menarche. We conclude the following: (1) from midpuberty to menarche, the increase in bone mass formation is highest at all skeletal sites in white girls; (2) early mature girls at the onset of puberty have slightly but definitely lower bone masses at all skeletal sites and at all pubertal stages than late mature girls, whereas the average bone mass formation from the onset of puberty to menarche is similar in both groups; (3) girls with a slow rate of pubertal maturation have lower bone mass values 2 years after the onset of puberty, but at menarche bone mass is similar compared with fast maturers; and (4) it cannot be confirmed that there is an effect of menarcheal age on bone mass values at menarche.

Adolescents: at increased risk for osteoporosis?

Perhaps the most important factor in the primary prevention of osteoporosis is the attainment of an optimal peak bone during adolescence. In addition to endogenous factors, such as genetic and ethnic background, environmental factors such as dietary habits, physical activity, and sex hormone therapy, influence the accretion of bone mass during this critical period of skeletal growth. First, calcium dietary intake in adolescents is generally well less than the current recommended RDA of 1200 mg/day. Multiple studies of children and adolescents have demonstrated increases in bone mass with dietary calcium supplementation. Second, regarding physical activity, the overall impression is that a moderate amount of particularly weight-bearing exercise has a positive impact on bone. There appears, however, to be a threshold of intensity of physical activity over which a negative impact on bone occurs, particularly when the exercise is of an anaerobic nature or occurring in very thin, amenorrheic participants. Third, previous research suggests that the various forms of hormonal contraception exert differing effects on bone mass in adolescents, with levonorgestrel implants and combined oral contraceptives may be associated with a more positive effect on bone mass compared with that observed with depot medroxyprogesterone acetate. From a clinical perspective, approaches to optimizing peak bone mass in adolescents would include increasing calcium intake, whether in the form of dairy products, fortified foods, or supplements as well as encouraging participation at a moderate level, in weight-bearing exercise. Last, in adolescents with extensive risk factors and predicted long duration of use, subdermal implants or combined oral contraceptives may be the optimal hormonal methods of birth control.

Precocious puberty and body composition: effects of GnRH analog treatment

INTRODUCTION

Body composition changes with age and sex differences become significant only after puberty. Boys and girls before the age of 8 yr do not differ in fat, lean or bone mineral mass. Hormonal influences during pubertal development determine the physiological adult male and female body composition phenotype.

AIM

The aim of our study was to evaluate body composition changes due to central precocious puberty (PP) and the specific effects of therapy on these modifications.

SUBJECTS AND METHODS

Sixteen patients (14 girls, 2 boys) were included in the study. They were diagnosed as affected by idiopathic PP according to standard hormonal and clinical criteria; anatomic alterations of hypothalamus-hypophysis region were excluded by MRI. Mean age at diagnosis was 5.9 +/- 1.9 yr. All patients received GnRH analog (Leuprolide or Triptorelin) treatment subcutaneously every 4 weeks for at least 1 yr. Mean period of treatment was 3.4 +/- 1.9 yr. Standard anthropometry and body composition analysis were performed at baseline and every 6-12 months. A group of healthy subjects with normal timing of puberty was matched (for age or for pubertal stage) served as the control group (CA or CP, respectively).

RESULTS

Patients with PP showed at baseline a significant increase of BMI and relative body weight; lean and fat compartments were also increased but not significantly. During treatment, the PP group showed increased fat mass compared to CA (p<0.05), while no difference was found between PP and CP. Lean mass was similar to CA but lower than in CP (p<0.05). During treatment a significant increase in lean mass (both as total as well as limb mass) was observed. After stopping treatment there was no difference between PP and CP, except for lower lean mass (p<0.04).

CONCLUSION

When puberty occurs precociously, lean and fat mass are not significantly different from age-matched control subjects. Data collected during treatment confirm a shortening of prepubertal lean mass development and the block of further lean mass development due to puberty itself, while fat mass accumulation continues. The net result of these modifications determines a typical body composition pattern in PP patients, after the end of therapy: lean mass is reduced by a shortening of the prepubertal growing period and by the "menopausal effect" of treatment itself. Fat mass is increased as a consequence of therapy and could lead to future obesity.

Bone mineral in prepubertal children: gender and ethnicity

Previous reports of gender and ethnic differences in bone mineral in prepubertal children have been inconsistent due to different methodologies, the problematic nature of bone density by dual-energy X-ray absorptiometry (DXA) calculated as the ratio of bone mineral mass to projected bone area (BA), and the generally small study populations. The aim of this study was to test the hypothesis that gender and ethnic differences in bone mineral by DXA are present in prepubertal children. The subjects were 336 healthy Asian, black, and white prepubertal children (172 females and 164 males). Total body bone mineral content (TBBMC) was adjusted for total body BA (TBBA), age, height, and weight. Adjusted mean TBBMC was greater in males than in females (p = 0.01). The gender difference was independent of ethnicity. Adjusted mean TBBMC was different for black compared with nonblack children (p = 0.001). The ethnic difference was a function of TBBA and weight. This study in a multiethnic population of prepubertal children shows (1) a gender difference in TBBMC and (2) an ethnic difference in TBBMC.

Body mass index (BMI) in Turner Syndrome before and during growth hormone (GH) therapy

OBJECTIVE

To study whether body mass index (BMI) is different in girls with Turner syndrome (TS) compared to normal girls, and whether BMI in TS is affected by growth hormone (GH) treatment.

DESIGN

A retrospective cross-sectional study.

SUBJECTS

2468 girls with TS enrolled in the National Cooperative Group Study (NCGS), a collaborative surveillance study for assessing GH-treated children.

MEASUREMENTS

BMI and BMI standard deviation score (BMI SDS) at baseline and during GH treatment were computed from height and weight data.

RESULTS

BMI in TS patients increases with age as expected. However, BMI SDS increased starting at about age 9 y. A similar pattern of increase in BMI SDS was observed after each year of GH treatment for up to 4 y, but GH treatment did not change the magnitude of increase. BMI and BMI SDS curves before and during GH treatment were essentially superimposable.

CONCLUSION

These findings suggest that mechanisms specific for TS are responsible for the age-related increase in BMI SDS. This increase was unaffected by GH treatment.

Longitudinal bone mineral density changes in female child artistic gymnasts

Changes in bone mineral density (BMD), and related factors, in female child artistic gymnasts (n = 9) and their age- (+/-0.3 years), height- (+/-2.8 cm), and weight- (+/-1.7 kg) matched controls (n = 9) were prospectively examined. It was hypothesized that gymnasts would possess higher BMD at baseline, 6, and 12 months later and have greater gains in BMD over 1 year compared with controls. BMD (g/cm2) of the total proximal femur (TPF), Ward's triangle (WT), trochanter (Troch), femoral neck (FN), lumbar spine (LS, L1-L4), and total body (TB) were measured by dual-energy X-ray absorptiometry. Physical activity was measured by a 7-day recall; daily dietary intakes of energy and nutrients were estimated from 3-day records. Serum osteocalcin and urinary pyridinium cross-links were measured by radioimmunoassay and high performance liquid chromatography, respectively. Gymnasts versus controls possessed significantly higher BMD at all sites measured. Although not significantly different (p > 0.05), gymnasts compared with controls had moderately larger percentage changes in Troch (% Delta = 8.6 +/- 3.0 vs. 3.8 +/- 5.1%, d = 0.41), FN (% Delta = 6.1 +/- 1.2 vs. 3.9 +/- 1.6%, d = 0.55), LS (% Delta = 7.8 +/- 1.1 vs. 6.8 +/- 1.6%, d = 0.26), and TB BMD (% Delta = 5.6 +/- 0.8 vs. 3.4 +/- 0.7%, d = 0.98) as evidenced by the magnitude of the effect sizes (d). Gymnasts versus controls possessed a lower percentage body fat (p < 0.01) and engaged in more hours of very hard activity (p < 0.0001). Calcium, as a percentage of adequate intake, decreased over 12 months (p < 0.01), and urinary cross-links significantly decreased over 6 months in both groups. Female child gymnasts possess higher BMD at the TPF and related sites, LS, and TB compared with nongymnast controls, and 1 year of gymnastics training moderately increases Troch, FN, LS, and TB BMD for gymnasts compared with controls. These findings lend support to the idea that gymnastics training in childhood helps maximize peak BMD.

Determination of body composition in African-American children: validation of bioelectrical impedence with dual energy X-ray absorptiometry

Body compositional differences between Black and White adults are well-known. It has become increasingly apparent that these racial variations may begin in childhood. Previously, our group validated tetrapolar bioelectrical impedance (BIA) measurements against H2(18O) dilution method to develop prediction formulas of fat free mass (FFM) in healthy White-American children: FFM = 0.524 Ht2/R + 0.415 Wt 0.32. In the present study we used BIA to establish a FFM prediction equation for forty African-American children (19 males and 21 females). Of the females, six were diagnosed with polycystic ovary syndrome (PCOS) and were obese. FFM was determined by dual energy X-ray absorptiometry (DEXA). Impedence measurements by BIA showed a strong correlation with FFM determined by DEXA. In healthy Black children, FFM = 0.84 Ht2/R + 1.10 with a standard error of estimate (SEE) of 1.47 kg (R2 = 0.97). In Black females with PCOS, FFM = 0.62 Ht2/R + 0.21 Wt - 1.94 with a SEE of 1.43 kg (R2 = 0.99). The observed differences in the prediction equations of FFM between White-American and African-American children underline the importance of using race-specific formulas in evaluating body composition. With the overall increase in rates of childhood obesity and more so in the Black race, BIA is an easy and useful tool for the assessment and follow up of body compositional changes with lifestyle interventions.

Body composition, dietary intake, and energy expenditure in nonobese, prepubertal children of obese and nonobese biological mothers

OBJECTIVE

To determine differences in dietary intake, resting energy expenditure, activity level, fat-free mass, and percentage body and abdominal fat in nonobese children of obese mothers compared with nonobese children of nonobese mothers.

DESIGN

Cross-sectional comparison study. Children's food diaries were analyzed to determine average energy and nutrient content. Resting energy expenditure of children was measured by means of indirect calorimetry. Children's activity levels were estimated through questionnaires administered during interviews. Dual-energy x-ray absorptiometry was used to estimate body composition of children.

SUBJECTS

Mothers of subjects responded to advertisements and were recruited as nonobese (body mass index = 20 to 25) or obese (body mass index > or = 30). Offspring included in the study were prepubertal and nonobese (10th to 90th percentile of weight for height by gender). Twelve pairs of children could be matched for weight, gender, and age.

STATISTICAL ANALYSIS PERFORMED

Wilcoxon signed rank tests were used to determine differences between the 2 groups of children.

RESULTS

Percentage abdominal fat was greater (median difference = 3.15, P = .001) and fat-free mass was lower (median difference = 1.19, P = .04) in children of obese mothers compared with children of nonobese mothers. No statistically significant differences between the 2 groups of children were found for dietary intake, resting energy expenditure, activity level, or percentage body fat.

APPLICATIONS/CONCLUSIONS

The significantly higher percentage of abdominal fat and lower fat-free mass in children of obese mothers may contribute to obesity onset. Use of dual-energy x-ray absorptiometry as a screening tool for nonobese, prepubertal children with an obese parent will help to identify those at risk. Education and lifestyle changes can then be implemented to help prevent the onset of obesity.

Serum leptin levels in males with delayed puberty during short-term pulsatile GnRH administration

Leptin may be a possible trigger for puberty. In normal males, it has been shown that leptin increases from the pre-pubertal to the early pubertal stage, and then declines in the late pubertal stage. We examined leptin levels in six male adolescents (mean age 16.3+/-0.6 yr; range 14.2-17.6 yr) with delayed puberty (constitutional delay of puberty no.=2; idiopathic hypogonadotropic hypogonadism no.=4) during 120 days of subcutaneous pulsatile GnRH administration. A group of subjects in pre-puberty (no.=11), early-puberty (n=10) and mid-puberty (no.=7) were evaluated as controls. Morning blood samples were taken for determination of leptin, testosterone, LH and FSH levels. In delayed puberty subjects blood samples were taken every 30 days after the start of GnRH administration. At each examination BMI and testicular volume were evaluated. A follow-up examination was performed in the 6 patients 1.3-7.5 yr after the end of the 120 days of GnRH therapy. At baseline evaluation in delayed puberty mean leptin levels were 11.3+/-2.0 microg/l (median 11.3 microg/l; range 4.7-17.3 microg/l) and were higher than those found in pre-puberty (p=0.04) and mid-puberty (p=0.001). During GnRH administration there was no change in BMI and leptin levels but there was an increase in gonadotrophin levels, testosterone and testicular volume. One hundred and twenty days after, mean serum leptin were 10.1+/-2.1 microg/l (median 9.1 microg/l; range 3.4-16.8 microg/l). At the end of the study, leptin levels were higher in delayed puberty than in mid-puberty (p=0.002). At the follow-up examination leptin levels were 4.3+/-1.3 microg/l (median 3.4 microg/l; range 1.4-9.1 microg/l) (p=0.03 vs end of 120 days GnRH therapy) while testosterone and BMI were not changed. In conclusion 120-day pulsatile GnRH administration induced in males with delayed puberty physiological-like pubertal changes but not the decline in leptin levels reported during the progression of puberty. Therefore, in males with delayed puberty an impairment in the phenomenon of leptin decline associated with progression of puberty could be suggested. However after retrospective diagnosis of pubertal delay and long-term therapy in subjects with idiopathic hypogonadotropic hypogonadism leptin levels declined. These data seem to indicate that time more than increase in testosterone levels and testicular volume is the determinant of leptin decline at puberty.

Gender-related differences in the relationship between densitometric values of whole-body bone mineral content and lean body mass in humans between 2 and 87 years of age

The mineral, lean, and fat contents of the human body may be not only allometrically but also functionally associated. This report evaluates the influence of muscle mass on bone mass and its age-related changes by investigating these and other variables in both genders in the different stages of reproductive life. We have analyzed the dual-energy X-ray absorptiometry (DEXA)-determined whole-body mineral content (TBMC), lean body mass (LBM), and fat body mass data (FBM) of 778 children and adolescents of both genders, aged 2-20 years [previously reported in Bone 16(Suppl.): 393S-399S; 1995], and of 672 age-matched men and women, aged 20-87 years. Bone mass (as assessed by TBMC) was found to be closely and linearly associated with muscle mass (as reflected by LBM) throughout life. This relationship was similar in slope and intercept in prepubertal boys and girls. However, while keeping the same slope of that relationship (50-54 g increase in TBMC per kilogram LBM): (1) both men and women stored more mineral per unit of LBM within the reproductive period than before puberty (13%-29% and 33%-58%, respectively); (2) women stored more mineral than age-matched men with comparable LBM (17%-29%) until menopause; and (3) postmenopausal women had lower values of bone mineral than premenopausal women, similar to those of men with comparable LBM. Men showed no age effect on the TBMC/LBM relationship after puberty. Multiple regression analyses showed that not only the LBM, but also the FBM and body height (but not body weight), influenced the TBMC, in that decreasing order of determining power. However, neither the FBM nor body height could explain the pre/postpubertal and the gender-related differences in the TBMC/LBM relationship. Accordingly: (1) calculated TBMC/LBM and FBM-adjusted TBMC/LBM ratios were lower in girls and boys from 2-4 years of age until puberty; (2) thereafter, females rapidly reached significantly higher ratios than age-matched men until menopause; and (3) then, ratios for women and age-matched men tended to equalize. A biomechanical explanation of those differences is suggested. Sex hormones or related factors could affect the threshold of the feedback system that controls bone remodeling to adapt bone structure to the strains derived from customary mechanical usage in each region of the skeleton (bone "mechanostat"). Questions concerning whether the mineral accumulation in women during the reproductive period is related or not to an eventual role in pregnancy or lactation, or whether the new bone is stored in mechanically optimal or less optimal regions of the skeleton, are open to discussion.

The impact of reversible gonadal sex steroid suppression on serum leptin concentrations in children with central precocious puberty

Serum leptin concentrations increase during childhood in both sexes. During sexual maturation, levels rise further in girls, but decrease in boys. These data suggest that testosterone either directly suppresses leptin levels or induces changes in body composition that result in lower leptin concentrations. To examine further the relationship between sex steroids and leptin, we performed a longitudinal study in children with central precocious puberty (28 girls and 12 boys) before, during, and after discontinuation of GnRH agonist-induced pituitary-gonadal suppression. Nighttime and daytime leptin levels were measured to determine whether the activity of the pituitary-gonadal axis affects their diurnal variation. In the boys, suppression of testosterone increased leptin levels, whereas resumption of puberty was associated with decreased leptin levels [3.5 +/- 0.8 vs. 9.5 +/- 3.1 ng/dL (P = 0.005) and 12.2 +/- 4.5 vs. 7.0 +/- 2.6 ng/dL (P = 0.012), respectively]. Serum leptin levels did not change in the girls with alteration of the pituitary-ovarian axis and consistently exceeded those in boys. Nighttime levels were consistently greater than daytime values by an average of 38.3% in the girls and 29.4% in the boys. These serial observations during reversible pituitary-gonadal suppression suggest that testosterone decreases leptin concentrations, but that estrogen, at least in this childhood model, has no discernible effect. In addition, our data indicate that the presence of the diurnal rhythm in leptin concentrations is independent of the state of the reproductive axis.

Body composition measurement: a review of hydrodensitometry, anthropometry, and impedance methods

Human body composition is an expression of genetic and nutritional factors. It can change as a consequence of exogenous influences such as training, disease, or diet and is therefore of particular interest to nutrition professionals. Two of the main methods of estimating body composition in this review (hydrodensitometry and anthropometry) have been in use for decades, but the third method (bioelectrical impedance) is more recent. The procedure, theoretical basis, assumptions, standard error of estimates, and comparisons with other techniques are presented for each of the three methods. References to general and specific populations are presented that illustrate regression equations for different ages, ethnic groups, and gender. The advantages and disadvantages of the three methods are reviewed with reference made to the alternative compartment models. Other methods (DEXA, infrared interactance) are briefly reviewed.

Bone mineral density and body composition before and during treatment with gonadotropin-releasing hormone agonist in children with central precocious and early puberty

Major changes in bone mineral density (BMD) and body composition occur during puberty. In the present longitudinal study, we evaluated BMD and calculated volumetric BMD [bone mineral apparent density (BMAD)], bone metabolism, and body composition of children (32 girls and 2 boys) with central precocious and early puberty before and during treatment with GnRH agonist (GnRH). Patients were studied at baseline and during treatment for 6 months (n = 34), 1 yr (n = 33), and 2 yr (n = 16). Lumbar spine and total body BMD and body composition were measured with dual-energy x-ray absorptiometry. The variables were compared with age- and sex-matched reference values of the same population and expressed as SD score (SDS). Bone age was assessed. Serum calcium, phosphate, alkaline phosphatase, osteocalcin, the carboxyterminal propeptide of type I collagen (PICP), cross-linked telopeptide of collagen I (ICTP), 1,25 dihydroxyvitamin D and urinary hydroxyproline/creatinine, and calcium/ creatinine ratios were measured. Mean lumbar spine BMD SDS was significantly higher than zero at baseline (P < 0.02) and did not differ from normal, after 2 yr of treatment. Mean spinal BMAD SDS and total body BMD SDS were not significantly different from zero at baseline and had not changed significantly after 2 yr of treatment. During therapy, fat mass and percentage body fat SDS increased, whereas lean tissue mass SDS decreased. Mean lumbar spine BMD and BMAD and total body BMD SDS, calculated for bone age, were all lower than zero at baseline (BMD P < 0.001 and BMAD P < 0.05) and also after 2 yr treatment (respectively, P < 0.001, P < 0.05, and P < 0.01). Biochemical bone parameters were significantly higher than prepubertal values at baseline, and they decreased during treatment. In conclusion, patients with central precocious and early puberty had normal BMD for chronological age but low BMD for bone age, after 2 yr of treatment with GnRH. Bone turnover decreased during treatment. Changes in body composition resembled those seen in patients with GH deficiency.

Body composition of a young, multiethnic, male population

The study objective was to establish the range of total body-composition values for a young, multiethnic, healthy male population (aged 3-18 y) by using dual-energy X-ray absorptiometry (DXA). Results for 297 males in three ethnic groups [European American (white), n = 145; African American (black), n = 78; and Mexican American (Hispanic), n = 74] are reported. Bone mineral content (BMC), lean tissue mass (LTM), body fat mass, and percentage fat are presented as functions of age. Analysis of variance with age, weight, and height as covariates was used to evaluate differences among the three ethnic groups. BMC and LTM were higher in black than in white males, but no difference in BMC or LTM was evident between the white and Hispanic groups. The relation between total-body BMC and LTM was linear (r = 0.985, P < 0.0001) and independent of age or ethnic classification. The Hispanic males had higher body fat values than the white group, whereas the black males generally had lower values than the white group. When adjusted for body size, the Hispanic males continued to have significantly higher body fat and percentage fat than the white or black males. Ethnic-specific equations for the prediction of body composition as a function of age, weight, and height were derived. The results for the white males in the present study were compared with DXA-derived reference data reported in other countries for young white males. We conclude that reference values of total body composition for young healthy males need to be ethnic specific.

Bone mineral density in adolescents. Higher values in a rural area--a population-based study of 246 subjects in southern Sweden

We performed, in a cross-sectional study, dual energy X-ray absorptiometry (DXA) among 15-16-year-old boys (n 58) and girls (n 44) living in an urban area and among boys (n 82) and girls (n 66) of the same age from a rural area. We measured bone mineral density (BMD) of the total body, the lumbar spine and the hip. In the rural population, we found significantly higher BMD levels in the lumbar spine (14% for the boys and 12% for the girls) and the total body (6.9% for the boys and 3.4% for the girls). We detected no significant differences in the hip BMD. Adolescents in rural areas seem to develop a higher peak bone mass and thereby presumably have a lower risk of developing fragility fractures.