Percentiles of body composition from bioelectrical impedance and body measurements in U.S. adolescents 8-17 years old: Project HeartBeat!

BODYFAT: a new calculator to determine the risk of being overweight validated in Spanish children between 11 and 17 years of age

The assessment of body fat of children in primary care requires consideration of the dynamic changes in height, weight, lean mass, and fat mass during childhood growth. To achieve this, we aim to develop a predictive equation based on anthropometric values, with optimal diagnostic utility. This is a cross-sectional observational study, involving schoolgoers aged 11-17 years in the Vigo metropolitan area. Out of 10,747 individuals, 577 were randomly recruited.

VARIABLES

age, sex, ethnicity/country of origin, weight, height, 8 skinfolds, 3 diameters, 7 perimeters, and 85% percentile of body fat mass as the gold standard. Generalized additive regression was selected by cross-validation and compared using receiver operating characteristic curves (ROC curves). Sensitivity, specificity, positive and negative predictive values, true positive and true negative values, false positive and false negative values, accuracy, and positive and negative likelihood ratios were calculated. Two models were identified. The optimal model includes sex, weight, height, leg perimeter, and arm perimeter, with sensitivity of 0.93 (0.83-1.00), specificity of 0.91 (0.83-0.96), accuracy of 0.91 (0.84-0.96), and area under the curve (AUC) of 0.957 (0.928-0.986). The second model includes sex, age, and body mass index, with sensitivity of 0.93 (0.81-1.00), specificity of 0.90 (0.80-0.97), accuracy of 0.90 (0.82-0.96), and an AUC of 0.944 (0.903-0.984).

CONCLUSION

Two predictive models, with the 85th percentile of fat mass as the gold standard, built with basic anthropometric measures, show very high diagnostic utility parameters. Their calculation is facilitated by a complementary online calculator.

WHAT IS KNOWN

• In routine clinical practice, mainly in primary care, BMI is used to determine overweight and obesity. This index has its weaknesses in the assessment of children.

WHAT IS NEW

• We provide a calculator whose validated algorithm, through the determination of fat mass by impedanciometry, makes it possible to determine the risk of overweight and obesity in the community setting, through anthropometric measurements, providing a new practical, accessible and reliable model that improves the classification of overweight and obesity in children with respect to that obtained by determining BMI.

Percent Body Fat and Weight Status of Youth Participating in Pediatric Weight Management Programs in the Pediatric Obesity Weight Evaluation Registry

Factors associated with change in percent body fat (%BF) of children in pediatric weight management (PWM) care may differ from those associated with change in weight status. Objective: To describe %BF and weight status at initial visits to 14 PWM sites, identify differences by sex, and evaluate factors associated with change over 6 months. Methods: Initial visits of 2496 males and 2821 females aged 5-18 years were evaluated. %BF was measured using bioelectrical impedance analysis. Results: Sex-specific logistic regressions [806 males (32.3%), 837 females (29.7%)] identified associations with primary outcomes: lower %BF and metabolically impactful ≥5-point drop in percent of the 95th BMI percentile (%BMIp95) over 6 months. At the initial visit, males had lower %BF and higher %BMIp95 than females. Over 6 months, males had significantly (p < 0.001) greater median drop in %BF (-1.4% vs. -0.4%) and %BMIp95 (-3.0% vs. -1.9%) and a higher frequency of decreased %BF (68.9% vs. 57.8%), but similar percentage with ≥5-point %BMIp95 drop (36.5% vs. 32.4%; p = 0.080). For males, factors significantly associated with decreased %BF (older age, ≥6 visits, lack of developmental or depression/anxiety concerns) were not related to having a ≥5-point %BMIp95 drop. For females, lack of depression/anxiety concern was significantly associated with decreased %BF but was not associated with ≥5-point %BMIp95 drop. Conclusions: There are differences by sex in initial visit %BF and %BMIp95 and in characteristics associated with changes in these measures. PWM interventions should consider evaluating body composition and sex-stratifying outcomes.

First body fat reference curves for Macedonian children and adolescents: the MAKFIT study

Introduction

Introduction: childhood obesity is a worldwide chief health problem. Along with body mass index, body fat percentile values can also be used to predict future cardiovascular and metabolic health risks. Objective: the study's aim is to define the percentile values and curves about the fat tissue percentage through which the childhood and adolescent overweight/obesity in the Republic of North Macedonia will be diagnosed. Methods: the research was conducted on a sample of 15,075 children and adolescents aged six to 14 years (7,627 boys and 7,448 girls). Body fat percentage was established by bioelectrical impedance. The LMS method was used in percentile values and curves' construction. Results: the boys' 50th percentile curve shows that the body fat percentage average value has a slight growth from seven to ten years of age, but after their 10th it begins to drop continuously until the age of 14 years. At the same time, the girls' body fat percentage average value increases continuously from six to 14 years of age. Conclusion: since body mass index cannot always establish body fat content, the direct assessment of body fat by bioelectrical impedance would be of great advantage for pediatric and clinical decisions. Therefore, the study provides referent percentile norms for the body fat percentage of healthy Macedonian children and adolescents. For this purpose, a practical and clinically applicable method was used. The obtained referent percentile norms can be useful in assessing overweight and obesity in Macedonian children and adolescents.

Myocardial function, mechanics and work by echocardiography in adolescents with severe obesity

Introduction

Obesity and its metabolic complications can impact the heart's structure and function in childhood, although demonstrating this impact has been challenging. New echocardiographic parameters such as left atrial strain (LAε) and left ventricular strain (LVε), as well as myocardial work (MW), could reveal subclinical alterations in cardiac function.

Objective

The aim is to evaluate the feasibility of these parameters in adolescents with severe obesity and explore their associations with body fat, metabolic comorbidities, and physical capacity.

Methods

This is a cross-sectional study in adolescents with obesity who underwent echocardiography with analysis of LAε, LVε and MW using speckle tracking. Feasibility and association with anthropometry, body fat percentage, comorbidities and cardiopulmonary test were analyzed.

Results

Twenty adolescents were recruited, 13 (65%) were males, median age 14.2 (interquartile range: 12.9-14.9) years old. The median Z-score for BMI (zBMI) was +3.03 (2.87-3.14), 14 (70%) had severe obesity (zBMI ≥+3), 12 (60%) body fat ≥95th percentile, 9 (45%) high blood pressure (HBP) and 8 (40%) metabolic syndrome. The analysis of the echocardiographic parameters was feasible in 95% (LAε) and 100% (LVε and MW). LVε was lower in adolescents with vs. without metabolic syndrome: 17.8% (17.5-19.3%) vs. 19.3% (18.3-20.3%), P = 0.046; and with vs. without HBP 17.8% (17.5-18.6%) vs. 19.7% (18.4-20.3%), P = 0.02. Those with body fat ≥95th percentile had lower LAε and MW parameters, without association with cardiopulmonary test.

Conclusion

Echocardiographic evaluation of LAε, LVε and MW is feasible in adolescents with severe obesity. A higher proportion of body fat and the presence of comorbidities are associated with alterations in these new echocardiographic functional parameters suggesting myocardial impact of higher metabolic compromise.

Body composition in early pubescent children with obesity: effects following 1 year of nonintervention

Little is known about whether body composition changes differently between children with and without obesity following 1 year of nonintervention. Therefore, we investigated body composition in early pubescent children (8-12 yr) with and without obesity before and after a period of 1 year of nonintervention. Early pubescent children (8-12 yr; Tanner stage ≤ 3) with (body mass index, BMI ≥ 95th percentile) and without obesity (15th < BMI < 85th percentile) were recruited. At baseline, 88 children (n = 25 without obesity) completed dual-energy X-ray absorptiometry imaging (DXA) for body composition measurements [%body fat, fat mass, fat-free mass (FFM)]. One year later, 47 participants (n = 15 without obesity) returned for repeat testing. The children without obesity were older (11.0 ± 1.0 vs. 10.0 ± 1.2 yr; means ± SD) (P = 0.013). There was no group difference in height, and both groups increased in height similarly after 1 year (147.7 ± 8.9 to 154.5 ± 9.2 cm without vs. 145.6 ± 5.8 to 152.5 ± 5.9 cm with obesity) (P < 0.001). Weight was greater (P < 0.001) in children with obesity at baseline as was the increase in weight after 1 yr (9.25 vs. 5.82 kg) (interaction, P = 0.005). Fat mass increased by 4.4 kg in children with obesity and by 1.1 kg in children without obesity (interaction, P < 0.001). However, there was no difference in fat-free mass between those with and without obesity at baseline (29.9 ± 5.9 vs. 31.6 ± 4.8 kg) (P = 0.206) with both groups increasing similarly over 1 year (gain of 4.87 vs. 4.85 kg with and without obesity, respectively). Without intervention, the increase in fat mass is four times greater in children with obesity after 1 year as compared with children without obesity.NEW & NOTEWORTHY Little is known about changes in body composition in children with and without obesity following 1 year of nonintervention. We report that without intervention, fat mass gain is significantly greater in children with obesity after 1 year compared with those without obesity. Body mass index (BMI) and %body fat measurements after 1 year yielded no significant increase suggesting that BMI and %fat alone are not suitable measures for tracking changes in adiposity among children.

The relationship in early childhood body composition and physical activity levels regarding fundamental motor skill development

BACKGROUND

Fundamental motor skills (FMS) are considered essential for sport participation and might be deficit in obese children. While evidence indicates that physical activity (PA) levels impact motor skill development, the relationship between body composition, PA, and motor competence, particularly in early childhood, is not thoroughly understood. We aimed to determine if PA, fat mass (FM), and fat-free mass (FFM) are predictors of FMS.

METHODS

Preschoolers (n = 47) from two preschools were assessed for FMS, PA, and body composition. Peabody Developmental Motor Scales (PDMS-2) subscale scores were used to assess FMS. PA was assessed with a wrist-worn accelerometer for five days during school. FM and FFM were measured with foot-to-foot bioelectrical impedance.

RESULTS

Linear regressions indicate significant models for stationary skills (SS) (F = 4.57, p = .004) and object manipulation skills (OMS) (F = 4.66, p = .003). FFM was the only significant predictor of SS (t = 3.98, p < .001) and OMS (t = 3.50, p = .001). FM and all intensities of PA were nonsignificant predictors in all models.

CONCLUSIONS

These results indicate that interventions that target improving or maintaining FFM may improve FMS.

More hypoglycemia not associated with increasing estimated adiposity in youth with type 1 diabetes

BACKGROUND

Despite the widespread clinical perception that hypoglycemia may drive weight gain in youth with type 1 diabetes (T1D), there is an absence of published evidence supporting this hypothesis.

METHODS

We estimated the body fat percentage (eBFP) of 211 youth (HbA1c 8.0-13.0%, age 13-16) at baseline, 6, and 18 months of the Flexible Lifestyles Empowering Change trial using validated equations. Group-based trajectory modeling assigned adolescents to sex-specific eBFP groups. Using baseline 7-day blinded continuous glucose monitoring data, "more" vs. "less" percent time spent in hypoglycemia was defined by cut-points using sample median split and clinical guidelines. Adjusted logistic regression estimated the odds of membership in an increasing eBFP group comparing youth with more vs. less baseline hypoglycemia.

RESULTS

More time spent in clinical hypoglycemia (defined by median split) was associated with 0.29 the odds of increasing eBFP in females (95% CI: 0.12, 0.69; p = 0.005), and 0.33 the odds of stable/increasing eBFP in males (95% CI: 0.14, 0.78; p = 0.01).

CONCLUSIONS

Hypoglycemia may not be a major driver of weight gain in US youth with T1D and HbA1c ≥8.0. Further studies in different sub-groups are needed to clarify for whom hypoglycemia may drive weight gain and focus future etiological studies and interventions.

IMPACT

We contribute epidemiological evidence that hypoglycemia may not be a major driver of weight gain in US youth with type 1 diabetes and HbA1c ≥8.0% and highlight the need for studies to prospectively test this hypothesis rooted in clinical perception. Future research should examine the relationship between hypoglycemia and adiposity together with psychosocial, behavioral, and other clinical factors among sub-groups of youth with type 1 diabetes (i.e., who meet glycemic targets or experience a frequency/severity of hypoglycemia above a threshold) to further clarify for whom hypoglycemia may drive weight gain and progress etiological understanding of and interventions for healthy weight maintenance.

Body-Fat-Percentile Curves for Thai Children and Adolescents

This study aimed to generate sex-specific percentile curves for the percentage of body fat (PBF) in Thai children using a bioelectrical impedance analysis (BIA). The secondary objective of this study was to determine the association between body fat and other anthropometric measurements. A cross-sectional study was conducted on 3455 Thai school children aged 6-18 years. The body-fat contents were measured using BIA. Smoothed percentile curves of PBF were derived using a scatter plot with a smooth curve fitted by the Loess method. The correlations between the body fat and the anthropometric measurements were assessed using the Spearman's rank correlation. The 50th and lower body-fat-percentile curves of the boys slowly increased until age 12, after which they slightly decreased until age 15 and then slightly increased until age 18. In the higher boys' percentiles, the body fat sharply increased until age 11 and then decreased until age 18. In the girls, the PBF percentiles increased steadily from 6 to 18 years. The body-mass index was strongly correlated with PBF and fat mass in both sexes. The waist-to-height ratios showed strong correlations with PBF and fat mass in the boys but were moderate in the girls. The use of PBF percentile curves can be an additional metric for the evaluation of obesity in Thai children.

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.

Anthropometric Indicators as a Tool for Diagnosis of Obesity and Other Health Risk Factors: A Literature Review

Obesity is characterized by the accumulation of an excessive amount of fat mass (FM) in the adipose tissue, subcutaneous, or inside certain organs. The risk does not lie so much in the amount of fat accumulated as in its distribution. Abdominal obesity (central or visceral) is an important risk factor for cardiovascular diseases, diabetes, and cancer, having an important role in the so-called metabolic syndrome. Therefore, it is necessary to prevent, detect, and appropriately treat obesity. The diagnosis is based on anthropometric indices that have been associated with adiposity and its distribution. Indices themselves, or a combination of some of them, conform to a big picture with different values to establish risk. Anthropometric indices can be used for risk identification, intervention, or impact evaluation on nutritional status or health; therefore, they will be called anthropometric health indicators (AHIs). We have found 17 AHIs that can be obtained or estimated from 3D human shapes, being a noninvasive alternative compared to X-ray-based systems, and more accessible than high-cost equipment. A literature review has been conducted to analyze the following information for each indicator: definition; main calculation or obtaining methods used; health aspects associated with the indicator (among others, obesity, metabolic syndrome, or diabetes); criteria to classify the population by means of percentiles or cutoff points, and based on variables such as sex, age, ethnicity, or geographic area, and limitations.

Body Composition versus BMI as Measures of Success in a Clinical Pediatric Weight Management Program

The high rates and long-term medical consequences of childhood obesity make it a public health crisis requiring effective diagnosis, treatment, and prevention. Although BMI is an adequate screening tool for obesity, monitoring BMI change is not always the best measure of success in treating patients in a pediatric weight management program. Our retrospective study evaluated the proportion of patients that achieved favorable changes in body composition by bioelectrical impedance analysis in the absence of improvements in BMI, BMI percentile, or percent of the 95th percentile for BMI. It was found that 30% of patients whose BMI increased by 1.0 kg/m2 or more, 31.6% of patients with stable or increasing BMI percentiles, and 28% with stable or increasing percent of the 95th percentile for BMI demonstrated an improvement in body composition (skeletal muscle mass and body fat percentage). Body composition is an important measure of success for a subset of patients who otherwise may believe that their efforts in lifestyle change have not been effective. Our results suggest that including body fat percentage as a measure of success in evaluating the progress of patients participating in a pediatric weight management program is appropriate and may more accurately track success than change in BMI or BMI percentile alone.

Antioxidant Enzymes Haplotypes and Polymorphisms Associated with Obesity in Mexican Children

Obesity is a major health problem worldwide and constitutes a sanitary emergency in Mexico, especially childhood obesity. Several studies have proved the relationship between obesity and oxidative stress and the influence of genetic predisposition. This work was aimed to analyze the association of antioxidant enzyme polymorphisms with overweight and obesity in Mexican children and adolescents. A case-control study was performed in 585 children and adolescents aged 3 to 17 years, using two criteria to classify obesity: body mass index (BMI) and body fat percentage (BFP). Anthropometric and biochemical measurements were carried out, and malondialdehyde serum levels were determined. Genotyping was done with the Axiom Genome-Wide LAT microarray, including 68 single nucleotide polymorphisms (SNPs) of the glutathione peroxidase (GPX) and paraoxonase (PON) families. We found six haplotypes associated with obesity—two of them (one in GPX3 and the other in GPX5 and GPX6) in a protective direction when obesity was classified by BMI. The other four haplotypes were associated with obesity when classification was based on BFP—one of them in GPX3 in a protective direction and the others in PON genes conferring obesity risk. In addition, two SNPs, GPX3 rs922429 and GPX4 rs2074451 showed protection against obesity classified by BFP. This study showed genetic susceptibility to oxidative stress in relation to obesity in Mexican children and opens up the possibility that some genetic loci related to obesity are not identified when weight classification is based on BMI.

Body fat accrual trajectories for a sample of Asian-Canadian and Caucasian-Canadian children and youth: A longitudinal DXA-based study

BACKGROUND

Body fat accrual trajectories can be used to monitor trends in body fat mass and identify potential health risks. Currently, no body fat percent (BF%) centile distance and velocity curves exist for Canadian youth.

OBJECTIVES

To develop sex-specific and ethnic-specific BF% centile distance and velocity curves for White and Asian-Canadian youth.

METHODS

We utilized 4734 observations from 944 participants (female = 487; Asian = 532) to create sex-specific BF% velocity curves for age 10 to 18 years and sex-specific and ethnic-specific BF% percentile distance curves for ages 9 to 18 years for White and Asian children. BF% was derived from whole body DXA scans.

RESULTS

BF% centile distance curves for Asian and White girls were similar. BF% at most centiles plateaued around age 16 for Asian but not for White boys. Velocity curves for boys declined from age 11 to 13 years and then increased until age 18 years. For girls from 10 to 15 years, velocity curves converged towards the 50th centile then remained flat from 16 to 18 years.

CONCLUSIONS

BF% distance and velocity centiles can be used to identify when an individual veers from an average BF% accrual trajectory. In future, these curves may be used to investigate differences in fat mass and accrual across Canada.

Obesity measured as percent body fat, relationship with body mass index, and percentile curves for Mexican pediatric population

In Mexico, the increase in childhood obesity is alarming. Thus, improving the precision of its diagnosis is expected to impact on disease prevention. We estimated obesity prevalence by bioimpedance-based percent body fat (%BF) and body mass index (BMI) in 1061 girls and 1121 boys, from 3 to 17 years old. Multiple regressions and area under receiver operating curves (AUC) were used to determine the predictive value of BMI on %BF and percentile curves were constructed. Overall obesity prevalence estimated by %BF was 43.7%, and by BMI it was 20.1%; it means that the diagnosis by BMI underestimated around 50% of children diagnosed with obesity by %BF (≥30% for girls, ≥25% for boys). The fat mass excess is further underestimated in boys than in girls when using the standard BMI classification. The relationship between %BF and BMI was strong in school children and adolescents (all cases R2>0.70), but not in preschool children (girls R2 = 0.57, boys R2 = 0.23). AUCs showed greater discriminative power of BMI to detect %BF obesity in school children and adolescents (all cases AUC≥0.90) than in preschool children (girls AUC = 0.86; boys AUC = 0.70). Growth percentile charts showed that girls aged 9-17 years and boys aged 8-17 years presented fat excess from the 50th percentile and above. We suggested to change the BMI cut-off for them, considering values at the 75th percentile as overweight, and values at the 85th percentile as obesity, as previously recommended for Mexican children. Improving obesity diagnosis will allow greater efficiency when searching for comorbidities in clinical practice.

Prenatal DDT exposure and child adiposity at age 12: The CHAMACOS study

OBJECTIVE

Using data from the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) birth cohort study, we assessed the association of in utero exposure to dichlorodiphenyltrichloroethane (DDT) and dichlorodiphenylethylene (DDE) with child adiposity at age 12.

METHODS

We included 240 children with o,p'-DDT, p,p'-DDT, and p,p'-DDE concentrations measured in maternal serum collected during pregnancy (ng/g lipid) and complete 12-year follow-up data. Age- and sex-specific body mass index (BMI) z-scores were calculated from CDC growth charts. Children with BMI z-scores ≥ 85th percentile were classified as overweight or obese.

RESULTS

At 12 years, BMI z-score averaged 1.09 (±1.03) and 55.4% of children were overweight or obese. Prenatal DDT and DDE exposure was associated with several adiposity measures in boys but not girls. Among boys, 10-fold increases in prenatal DDT and DDE concentrations were associated with increased BMI z-score (o,p'-DDT, adj-β=0.37, 95% CI: 0.08, 0.65; p,p'-DDT, adj-β = 0.26, 95% CI: 0.03, 0.48; p,p'-DDE, adj-β = 0.31, 95% CI: 0.02, 0.59). Results for girls were nonsignificant. The difference by sex persisted after considering pubertal status.

CONCLUSIONS

These results support the chemical obesogen hypothesis, that in utero exposure to DDT and DDE may increase risk of obesity in males later in life.

Overweight or Obesity, Gender, and Age Influence on High School Students of the City of Toluca's Physical Fitness

MATERIAL AND METHOD

This is a prospective, cross-sectional, and correlational study with a probabilistic sampling in which 150 teenagers from three different high schools from the city of Toluca, Mexico, aged 15-17, were assessed.

OBJECTIVE

To determine if weight, age, and gender have an influence on physical fitness evaluated with the EUROFIT and ALPHA-FITNESS batteries.

RESULTS

Women have a higher overweight and obesity rate than men (3 : 1). Adolescents who have normal weight have regular physical fitness (74.9%). When comparing genders we found that men have a higher mean than women in the tests, except for skinfold thickness and waist circumference. Age was only correlated with the plate tapping test (p = 0.001). There are significant differences in the standing broad jump test and the Course-Navette of the EUROFIT and ALPHA-FITNESS batteries (p = 0.000).

CONCLUSIONS

It is likely that regular physical activity, and not normal weight, helps generate healthy physical fitness. Male subjects had a higher mean than women, reporting a better physical fitness and more frequent physical activity.

Body fat percentage is more associated with low physical fitness than with sedentarism and diet in male and female adolescents

BACKGROUND

Obesity is a multifactorial disease and our understanding of this disease is still incomplete.

PURPOSE

The aim of this investigation was to examine the associations between body fat percentage and physical fitness, diet and active/sedentary behaviors in female and male adolescents.

METHODS

A cross-sectional study was carried out on a sample of 1389 Spanish adolescents (706 boys and 683 girls) aged between 14 and 17years. Individual body fat percentage was measured by means of bioelectrical impedance analysis and participants' physical fitness was determined by measuring cardiorespiratory fitness (20-m shuttle run test), muscular strength (handgrip dynamometry), muscular endurance (curl-up and 90° push up repetition tests) and muscular flexibility (sit-and-reach test). Daily physical activity, sedentary time and diet were estimated using validated and self-reported questionnaires. The participants were divided into quartiles based on their body fat percentage.

RESULTS

Boys and girls included in Q3 and Q4 presented lower values for cardiorespiratory fitness than Q1 (P<0.05). Boys and girls included in Q4 also presented lower values for muscular endurance than Q1 (P<0.05). Only boys in Q4 presented lower levels of physical activity than Q1 (P<0.05). Physical activity, physical fitness and diet can explain 30% of the variance for body fat percentage in boys and 17% in girls.

CONCLUSIONS

Female and male adolescents with a higher body fat percentage presented lower cardiorespiratory and muscular endurance fitness than leaner counterparts.

Height, weight, body composition, and waist circumference references for 7- to 17-year-old children from rural Portugal

The purpose of this study was (1) to develop references of height, weight, body mass index (BMI), waist circumference and body fat for rural Portuguese children and adolescents and (2) to compare these results with other international references. The sample comprised 3094 children and adolescents aged 7-17 years from Vouzela, a central region in Portugal. Height, weight, BMI, waist circumference and body fat were measured. Centile curves were constructed using the LMS method. The Vouzela sample showed similar height median values compared to Centers for Disease Control and Prevention (CDC) and World Health Organization (WHO) percentile curves but greater values for weight and BMI. Percent body fat 50th percentile was greater in Vouzela children and adolescents compared to their international peers, except for boys aged 8-12 years. Boys' waist circumference median values were similar to those from the USA, whilst girls were similar until 12 years of age, after which the differences increased with age. The percentile curves constructed provide population specific references for growth and body composition of children and adolescents from rural Portugal. It is expected that they will be a useful tool for clinical and public health settings in rural Portugal.

Body composition assessment using DXA in six-year-old children: the 2004 Pelotas Birth Cohort, Rio Grande do Sul State, Brazil

The aim of this study was to describe fat (FM) and lean body mass (LBM) in six-year-old children from the 2004 Pelotas Birth Cohort, stratified by gender. Dual-Energy X-ray Absorptiometry was used to measure FM and LBM, FM and LBM indexes, and percentage (%) of FM and LBM. Mean measures of adiposity were higher among girls (6.3kg, 4.2kg/m2 and 23.4% vs. 5kg, 3.3kg/m2 and 18%) while LBM measures were higher among boys (19.3kg, 13kg/m2 and 78.5% vs. 17.7kg, 12.2kg/m2 and 73.2%). In both boys and girls mean measures of adiposity increased with socioeconomic status and maternal education. Mean measures of adiposity were higher among white-skinned children while %LBM was higher among black-skinned children. Preterm compared to full-term children showed lower mean measures of adiposity and LBM. Female sex, white skin color and higher socioeconomic conditions are associated with higher adiposity in childhood.

Body fat percentiles of Brazilian adolescents according to age and sexual maturation: a cross-sectional study

BACKGROUND

The objective of this study was to determine body fat percentiles of adolescents in the city of São Paulo, Brazil, according to gender, age, and sexual maturation.

METHODS

This study involved 4,690 adolescents aged 10-15 years across 31 schools in the city of São Paulo. Sexual maturation was assessed in terms of Tanner stage. The body fat percentage was calculated using skinfold thickness. Percentile curves were calculated using the LMS (curve, mean, and coefficient of variation) method.

RESULTS

The mean body fat percentages were lower in boys aged 10-12 and 13-15 years than in girls. Body fat percentages decreased progressively with sexual maturation in boys, but increased in girls. The 85th, 95th, and 97th percentiles represent the cutoff points for moderately elevated, elevated, and very elevated body fat percentages, respectively, in pre-pubescent boys (85th, 95th, and 97th percentiles: 32.54, 95 41.04, and 97, respectively) and pubescent boys (31.09, 36.30, and 44.33, respectively). These cutoff points were lower in pre-pubescent girls (29.52, 35.01, and 41.82, respectively) and in the 97th percentile in pubescent girls (31.55, 36.20, and 41.86, respectively).

CONCLUSION

To our knowledge, these are the first body fat percentages cutoff points according to sexual maturation for adolescents aged 10-15 years in Brazil. Our results provide a significant contribution to the assessment of body composition in this population.

Percentiles of percentage body fat in german children and adolescents: an international comparison

Background:

Age- and gender-specific percentiles of body mass index in children and adolescents are a cornerstone categorizing overweight and obesity in youths worldwide. Since corresponding worldwide growth curves of percent body fat (% BF) are missing, the purpose was to contribute smoothed percentiles of percentage body fat from a large urban sample of German youths and to include them in actual national and international percentile curves.

Methods:

We estimated % BF in 22 113 German youths aged 3 to 18 years participating in yearly cross-sectional surveys of the PEP Family Heart Study Nuremberg between 1993 and 2007. Percentage body fat was calculated from skinfold thickness using Slaughter equations. Ten smoothed percentile curves were constructed for % BF using the LMS method significant.

Results:

The age- and gender-specific reference curves demonstrate a continuous age-dependent increase of percentage body fat from age 3 to 18 years in girls; whereas in boys, the percentile curves steeply increase from 5 to 11 years and thereafter slightly decrease. The shape of the percentile curves, the maxima among boys at puberty and the median % BF at age 18 years are consistent with most of the current growth curves. % BF in urban studies seems to be lower than in national surveys .

Conclusions:

More than these nine studies should contribute to worldwide-standardized growth charts for % BF to better define overweight and obesity in youth.

Body fatness or anthropometry for assessment of unhealthy weight status? Comparison between methods in South African children and adolescents

OBJECTIVE

A variety of methods are available for defining undernutrition (thinness/underweight/under-fat) and overnutrition (overweight/obesity/over-fat). The extent to which these definitions agree is unclear. The present cross-sectional study aimed to assess agreement between widely used methods of assessing nutritional status in children and adolescents, and to examine the benefit of body composition estimates.

DESIGN

The main objective of the cross-sectional study was to assess underweight, overweight and obesity using four methods: (i) BMI-for-age using WHO (2007) reference data; (ii) BMI-for-age using Cole et al. and International Obesity Taskforce cut-offs; (iii) weight-for-age using the National Centre for Health Statistics/WHO growth reference 1977; and (iv) body fat percentage estimated by bio-impedance (body fat reference curves for children of McCarthy et al., 2006). Comparisons were made between methods using weighted kappa analyses.

SETTING

Rural South Africa.

SUBJECTS

Individuals (n 1519) in three age groups (school grade 1, mean age 7 years; grade 5, mean age 11 years; grade 9, mean age 15 years).

RESULTS

In boys, prevalence of unhealthy weight status (both under- and overnutrition) was much higher at all ages with body fatness measures than with simple anthropometric proxies for body fatness; agreement between fatness and weight-based measures was fair or slight using Landis and Koch categories. In girls, prevalence of unhealthy weight status was also higher with body fatness than with proxies, although agreement between measures ranged from fair to substantial.

CONCLUSIONS

Methods for defining under- and overnutrition should not be considered equivalent. Weight-based measures provide highly conservative estimates of unhealthy weight status, possibly more conservative in boys. Simple body composition measures may be more informative than anthropometry for nutritional surveillance of children and adolescents.

Percentage of body fat cutoffs by sex, age, and race-ethnicity in the US adult population from NHANES 1999-2004

BACKGROUND

To date, there is no consensus regarding adult cutoffs of percentage of body fat or estimated cutoffs on the basis of nationally representative samples with rigorous body-composition measurements.

OBJECTIVE

We developed cutoffs of percentage of body fat on the basis of the relation between dual-energy x-ray absorptiometry-measured fat mass and BMI (in kg/m(2)) stratified by sex, age, and race-ethnicity by using 1999-2004 NHANES data.

DESIGN

A simple regression (percentage of body fat = β(0) + β(1) × 1 ÷ BMI) was fit for each combination of sex (men and women), 3 age groups (18-29, 30-49, and 50-84 y of age), and 3 race-ethnicity groups (non-Hispanic whites, non-Hispanic blacks, and Mexican Americans). Model fitting included a consideration of complex survey design and multiple imputations. Cutoffs of percentage of body fat were computed that corresponded to BMI cutoffs of 18.5, 25, 30, 35, and 40 on the basis of estimated prediction equations.

RESULTS

R(2) ranged from 0.54 to 0.72 for men (n = 6544) and 0.58 to 0.79 for women (n = 6362). In men, the percentage of body fat that corresponded to a BMI of 18.5, 25, 30, 35, and 40 across age and racial-ethnic groups ranged from 12.2% to 19.0%, 22.6% to 28.0%, 27.5% to 32.3%, 31.0% to 35.3%, and 33.6% to 37.6%, respectively; the corresponding ranges in women were from 24.6% to 32.3%, 35.0% to 40.2%, 39.9% to 44.1%, 43.4% to 47.1%, and 46.1% to 49.4%, respectively. The oldest age group had the highest cutoffs of percentage of body fat. Non-Hispanic blacks had the lowest cutoffs of percentage of body fat. Cutoffs of percentage of body fat were higher in women than in men.

CONCLUSIONS

Cutoffs of percentage of body fat that correspond to the current US BMI cutoffs are a function of sex, age, and race-ethnicity. These factors should be taken into account when considering the appropriateness of levels of percentage of body fat.

Body fat percentile curves for U.S. children and adolescents

BACKGROUND

To date, several studies have been published outlining reference percentiles for BMI in children and adolescents. In contrast, there are limited reference data on percent body fat (%BF) in U.S. youth.

PURPOSE

The purpose of this study was to derive smoothed percentile curves for %BF in a nationally representative sample of U.S. children and adolescents.

METHODS

Percent fat was derived from the skinfold thicknesses of those aged 5-18 years from three cross-sectional waves of the National Health and Nutrition Examination Survey (NHANES) IV (1999-2000, 2001-2002, and 2003-2004; N=8269). The LMS (L=skewness, M=median, and S=coefficient of variation) regression method was used to create age- and gender-specific smoothed percentile curves of %BF.

RESULTS

Growth curves are similar between boys and girls until age 9 years. However, whereas %BF peaks for boys at about age 11 years, it continues to increase for girls throughout adolescence. Median %BF at age 18 years is 17.0% and 27.8% for boys and girls, respectively.

CONCLUSIONS

Growth charts and LMS values based on a nationally representative sample of U.S. children and adolescents are provided so that future research can identify appropriate cut-off values based on health-related outcomes. These percentiles are based on skinfolds, which are widely available and commonly used. Using %BF instead of BMI may offer additional information in epidemiologic research, fitness assessment, and clinical settings.

Body fat reference curves for healthy Turkish children and adolescents

Childhood obesity is a major worldwide health problem. In addition to body mass index (BMI), body fat percentiles may be used to predict future cardiovascular and metabolic health risks. The aim of this study is to define new age- and gender-specific body fat centiles for Turkish children and adolescents. A total of 4,076 (2,276 girls, 1,800 boys) children and adolescents aged 6-18 years were recruited for this study. Total body fat was measured by a bioelectrical impedance noninvasive method. Body fat percentiles were produced by the LMS method. The body fat percentile curves of boys appear to rise from age 6 to 12 years and then slope downwards to age 15 years and then flatten off. The body fat % percentiles of girls increased until 14 years of age through 75th to 97th percentiles and then slope downwards, but through the third to 50th percentiles, they showed a downward slope after 14 years old.

CONCLUSIONS

Since BMI may not always reflect body fat content, direct assessment of adiposity by a practical method would be significantly useful for clinical decisions. Therefore, this study provides normative data for body fat percentage in healthy Turkish children and adolescents. To this goal we used a practical and clinically applicable method. These references can be useful for evaluation of overweight and obesity.

Developing waist-to-height ratio cut-offs to define overweight and obesity in children and adolescents

OBJECTIVE

The waist-to-height ratio (WHtR) assesses abdominal adiposity and has been proposed to be of greater value in predicting obesity-related cardiovascular health risks in children than BMI. The present study aims to develop WHtR cut-offs for overweight and obesity based on the 85th and 95th percentiles for the percentage body fat (%BF) in a cohort of children and adolescents.

DESIGN

Waist circumference (WC), height, triceps and subscapular skinfolds were used to calculate WHtR and %BF. Correlations between WHtR and %BF and WHtR/mid-abdominal skinfold were made. Receiver-operating characteristic (ROC) curve analysis was used to select WHtR cut-offs to define overweight and obesity. Subjects were grouped by WHtR cut-offs, and mean values for anthropometry, blood lipids and blood pressure (BP) variables were compared.

SETTING

Australian primary and secondary schools.

SUBJECTS

A total of 2773 male (M) and female (F) subjects of the 1985 Australian Health and Fitness Survey, aged 8-16 years.

RESULTS

Correlation coefficients between WHtR and %BF were M: r = 0.73, F: r = 0.60, P < 0.01 and WHtR/mid-abdominal skinfold were M: r = 0.78, F: r = 0.65, P < 0.01. WHtR of 0.46(M) and 0.45(F) best identified subjects with > or = 85th percentile for %BF and 0.48(M) and 0.47(F) identified subjects with > or = 95th percentile for %BF. When comparing the highest WHtR group to the lowest, both sexes had significantly higher means for weight, WC, %BF, TG (male subjects only), systolic BP (female subjects only) and lower means for HDL cholesterol (P < 0.05).

CONCLUSIONS

WHtR is useful in clinical and population health as it identifies children with higher %BF at greater risk of developing weight-related CVD at an earlier age.

Analytic methods in Project HeartBeat!

Project HeartBeat! (1991-1995) was an observational study of the development of cardiovascular disease (CVD) risk factors in childhood and adolescence using an accelerated longitudinal design. The purpose of this paper is to explain the analytic methods used in the study, particularly multilevel statistical models. Measurements of hemodynamic, lipid, anthropometric, and other variables were obtained in 678 children who were enrolled in three cohorts (baseline ages 8, 11, and 14 years) and followed for 4 years, resulting in data for children aged 8-18 years. Patterns of change of blood pressure, serum lipid concentration, and obesity with age, race, and gender were of particular interest. The design specified 12 measurements of each outcome variable per child. Multilevel models were used to account for correlations resulting from repeated measurements on individuals and to allow use of data from incomplete cases. Data quality-control measures are described, and an example of multilevel analysis in Project HeartBeat! is presented. Multilevel models were also used to show that there were no differences attributable to the cohorts, and combining data from the three age cohorts was judged to be reasonable. Anthropometric data were compared with national norms and shown to have similar patterns; thus, the patterns seen in the CVD risk factors may be generalized, with some caveats, to the U.S. population of children.

Nutrient intake and anthropometry in children and adolescents with Down syndrome--a preliminary study

OBJECTIVE

To assess nutrient intake and anthropometrical characteristics of children and adolescents with DS, in Northern Greece.

STUDY DESIGN

Cross-sectional study of 34 youngsters with DS. The sample was divided into two age groups, children aged 2-9 years and adolescents aged 10-18 years old. A 3-day food record was used to assess dietary intake. Body weight, height, WHR,% body fat, BMI, FMI, FFMI and z-scores were recorded for each participant.

RESULTS

All participants exhibited a high CHO and low fat diet. More than half of the participants reported having five meals daily and the majority exercised twice a week. A great majority was stunted and overweight according to general population growth charts and 22% of the adolescents were also obese. %Body fat, BMI, FMI and FFMI was higher in adolescents. Generally, younger participants presented lower overweight rates and consumed a diet more sufficient in micronutrients; however, WHR was similar in both age-groups, indicating a constant trend in weight distribution of DS patients.

CONCLUSIONS

Although children with DS are born with a genetic predisposition to become overweight, obesity is actually nurtured throughout childhood when they develop food choices and become more independent.

Body fat reference curves for children

OBJECTIVE

To refine the diagnosis of childhood obesity by creating new sex-specific centile curves for body fat and to base these references on a simple and affordable method that could be widely adopted in clinical practice and surveys.

DESIGN

Body fat was measured by bio-impedance in 1985 Caucasian children aged 5-18 years from schools in Southern England. Smoothed centile charts were derived using the LMS method.

RESULTS

The new body fat curves reflect the known differences in the development of adiposity between boys and girls. The curves are similar by sex until puberty but then diverge markedly, with males proportionately decreasing body fat and females continuing to gain. These sex differences are not revealed by existing curves based on body mass index. We present charts in which cutoffs to define regions of 'underfat', 'normal', 'overfat' and 'obese' are set at the 2nd, 85th and 95th centiles. These have been designed to yield similar proportions of overweight/overfat and obese children to the IOTF body mass index cutoffs.

CONCLUSIONS

Direct assessment of adiposity, the component of overweight that leads to pathology, represents a significant advance over body mass index. Our new charts will be published by the Child Growth Foundation for clinical monitoring of body fat, along with the software to convert individual measurements to Z-scores.

Anthropometric body fat composition reference values in Spanish adolescents. The AVENA Study

OBJECTIVE

To determine reference values for body mass index (BMI), sum of six skinfolds (sigma6 skinfolds) and body fat percentage (BF%) in Spanish adolescents aged 13-18 years, included in the AVENA Study (Alimentación y Valoración del Estado Nutricional en Adolescentes: Food and Assessment of the Nutritional Status of Adolescents).

DESIGN

Multicentre cross-sectional study.

SETTING

Representative sample of Spanish adolescents.

SUBJECTS

The population was selected by means of a multiplestep, simple random sampling. The final number of subjects included in the AVENA Study was 2859 adolescents; 2160 adolescents had a complete set of anthropometric measurements and were then included in this study (1109 males and 1051 females).

INTERVENTIONS

Weight, height and six skinfold thicknesses were measured. As indices of total adiposity, we calculated BMI, summation sigma6 skinfolds and BF% with the formulas described by Slaughter et al.

RESULTS

Sigma6 skinfolds and BF% in each age group were significantly higher in females than in males. In males, age showed a significant effect for BMI, sigma6 skinfolds and BF%; however, in females, the effect was only significant for BF%. The percentile distribution was more disperse towards higher sigma6 skinfolds and BF% values in males when compared with females.

CONCLUSIONS

The presented percentile values will help us to classify adolescents in comparison with a well-established reference population, and to estimate the proportion of adolescents with high or low adiposity amounts.

SPONSORSHIP

The AVENA-Study was supported by the Spanish Ministry of Health (FIS 00/0015), and grants from Panrico SA, Madaus SA and Procter and Gamble SA. This study was also supported by Instituto de Salud Carlos III (Spain), RCESP (C03/09) and Spanish Ministry of Education (AP2003-2128).