Relationships between the lean mass index and bone mass and reference values of muscular status in healthy Chinese children and adolescents

Reference ranges for body composition indices by dual energy X-ray absorptiometry from the Bone Mineral Density in Childhood Study Cohort

BACKGROUND

Body composition assessment aids evaluation of energy stores and the impact of diseases and interventions on child growth. Current United States pediatric reference ranges from the National Health and Nutrition Examination Survey (NHANES) include 20% of children with obesity, body mass index of ≥95th percentile.

OBJECTIVES

This study aimed to develop dual energy X-ray absorptiometry (DXA) based reference ranges in a diverse cohort with low-obesity prevalence from the Bone Mineral Density in Childhood Study (BMDCS).

METHODS

This is a secondary analysis of a longitudinal, prospective, observational cohort. Healthy children (height and BMI within 3rd to 97th percentiles, ages 5-19 y at enrollment), from 5 United States centers were measured annually for ≤7 visits. Whole body scans were acquired using Hologic scanners. A subsample underwent repeat measurements to determine precision. We generated reference ranges for appendicular and total lean soft tissue mass index (LSTM Index), fat mass index (FMI), and other body composition measures. Resulting curves were compared to NHANES and across subgroups. Sex and age-specific equations were developed to adjust body composition Z-scores for height Z score.

RESULTS

We obtained 9846 scans of 2011 participants (51% female, 22% Black, 17% Hispanic, 48% White, 7% Asian/Pacific Islander, and 6% with obesity). Precision (percent coefficient of variation) ranged from 0.7% to 1.96%. Median and-2 standard deviation curves for BMDCS and NHANES were similar, but NHANES +2 standard deviation LSTM Index and FMI curves were distinctly greater than the respective BMDCS curves. Subgroup differences were more extreme for appendicular LSTM Index-Z (mean ± SD: Asian -0.52 ± 0.93 compared with Black 0.77 ± 0.87) than for FMI-Z (Hispanic 0.29 ± 0.98 compared with Black -0.14 ± 1.1) and were smaller for Z-scores adjusted for height Z-score.

CONCLUSIONS

These reference ranges add to sparse normative data regarding body composition in children and adolescents and are based on a cohort with an obesity prevalence similar to current BMI charts. Awareness of subgroup differences aids in interpreting results.

Sarcopenia in youth

Recent research has revealed causes other than aging that may induce sarcopenia in young people, contrary to the long-studied age-dependent reduction in muscular mass and function. The risk of sarcopenia begins in early adulthood, resulting in exaggerated muscle dysfunction in later life. Despite its clinical significance, research on youth-onset sarcopenia is still in its infancy. Due to a paucity of epidemiologic data and standardized criteria for sarcopenia in youth, determining the prevalence of sarcopenia in the young population remains challenging. Based on the evidence, >1 in every 10 young adults of most ethnicities is estimated to have sarcopenia. This review summarizes the possible etiologies of sarcopenia in young populations, including metabolic syndrome, physical inactivity, inadequate nutrition, inherent and perinatal factors, vitamin D deficiency, endocrinopathy, an imbalance of gut microbiota, neuromuscular diseases, organ failure, malignancy, and other inflammatory disorders. This is the first review of the current knowledge on the importance, prevalence, diagnosis, and causes of sarcopenia in youth.

The relationship between obesity and bone mineral density in children and adolescents: analysis of the National Health and Nutrition Examination Survey

Childhood and puberty are important period for the skeleton grows. Fat mass, especially visceral adipose tissue, was negatively correlated with areal bone mineral density in children and adolescents. The present study suggests that fat mass, especially visceral adipose tissue, has a slightly negative association with bone development in children and adolescents.

PURPOSE

This study observed the relationship between fat mass and distribution, and areal bone mineral density (aBMD) in children and adolescents.

METHODS

A retrospective study was conducted on US children and adolescents aged 8-19 years. Whole body (less head) aBMD was evaluated. Height (Ht) adjusted Z-scores for aBMD were calculated.

RESULTS

After controlling for age, gender, race, and lean body mass index (LBMI) Z-score, there were significant negative associations between fat mass index (FMI) Z-score and aBMD Ht-Z-adjusted Z-score (β =  - 0.272, P < 0.001, R2 = 0.033). In the linear regression models with aBMD Ht-Z-adjusted Z-score as the dependent variable, the regression coefficients of android fat mass were - 0.241 (P < 0.05, R2 = 0.002), - 0.473 (P < 0.001, R2 = 0.036), and - 0.474 (P < 0.001, R2 = 0.038) for healthy weight, overweight, and obesity group, respectively. The regression coefficients of visceral adipose tissue (VAT) mass were - 0.218 (P > 0.05, R2 = 0.001), - 2.025 (P < 0.001, R2 = 0.044), and - 1.826 (P < 0.001, R2 = 0.039), and the regression coefficients of subcutaneous adipose tissue (SAT) mass were - 0.467 (P < 0.001, R2 = 0.004), - 0.339 (P < 0.01, R2 = 0.024), and - 0.347 (P < 0.001, R2 = 0.018) for healthy weight, overweight, and obesity group, respectively.

CONCLUSIONS

The present study suggests that fat mass has a slightly negative association with bone development in children and adolescents. Trunk fat accumulation, especially visceral adipose tissue, was correlated with the lower level of aBMD. This association was obvious in overweight and obese children.

Different associations between waist circumference and bone mineral density stratified by gender, age, and body mass index

Introduction

Investigations of the relationship between waist circumference (WC) and bone mineral density (BMD) have inconsistent and incomprehensive results.

We explored the association between WC and BMD at various sites in a large-scale population-based study.

Methods

We screened 5337 participants from National Health and Nutrition Examination Survey (NHANES) database. BMD was measured using dual-energy X-ray absorptiometry at various skeletal sites. The associations of WC with BMD were evaluated by weighted multivariable logistic regression models and conducted subgroup analyses for gender, age, and BMI. A weighted generalized additive model and a smooth curve fitting were performed to address non-linearity.

Results

Adjustments for all confounders, in males, WC was negatively correlated to BMD in different age and BMI groups (all the p < 0.05), except for in the lowest BMI group; in females, overall trends of relationships between WC and BMD were negative. However, statistical differences were insignificant in some cases. Additionally, every 1 cm increase in WC for individuals of all ages with normal BMI (18.5 ≤ BMI < 25) was associated with decrease in BMD at each skeletal site, as was the case for men with BMI ≥ 25 kg/m². For women, the negative association of WC with BMD was evident at the lumbar spine in the youngest age group (8 ≤ Age ≤ 18) with normal BMI.

Conclusions

The nonlinear associations between WC and BMD at various skeletal sites are gender-, age- and BMI-specific in the NHANES (2006–2006).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05736-5.

The relationship between metabolic syndrome and bone mineral density in adolescents: analysis of the National Health and Nutrition Examination Survey

OBJECTIVES

The purpose of this study was to observe the relationship between metabolic syndrome (MetS) and height (Ht) adjusted Z-scores for areal bone mineral density (aBMD) in adolescents.

METHODS

A retrospective study was conducted on the United States adolescents aged 12-17 years. Data were extracted from the National Health and Nutrition Examination Survey (NHANES) 2011-2012, 2013-2014 and 2015-2016 cycles. Ht adjusted Z-scores for aBMD were calculated.

RESULTS

A total of 969 adolescents (493 boys and 476 girls), aged 14.5 ± 1.7 years were enrolled in this study. After control for age, gender, race, 25-hydroxyvitamin D [25(OH)D], and lean body mass index (LBMI) Z-score, adolescents with MetS had significantly lower levels of total body (less head) aBMD Ht-Z-adjusted Z-score than adolescents with one, two components of MetS and without component of MetS (p<0.05) and significantly lower levels of lumbar spine aBMD Ht-Z-adjusted Z-score than adolescents with one component of MetS and without component of MetS (p<0.05). There were significantly negative associations between total body (less head) aBMD Ht-Z-adjusted Z-score and waist circumference (WC) (β=-0.027, p<0.001, R²=0.057) and homeostasis model assessment insulin resistance (HOMA-IR) (β=-0.225, p<0.001, R²=0.016). There were significantly negative associations between lumbar spine aBMD Ht-Z-adjusted Z-score and WC (β=-0.039, p<0.001, R²=0.058) and HOMA-IR (β=-0.251, p<0.001, R²=0.008).

CONCLUSIONS

The present study demonstrates that MetS may have a negative effect on bone mineral density in adolescents. Abdominal obesity and insulin resistance play a major role on the decline of aBMD in adolescents.

Sarcopenic Obesity in Children and Adolescents: A Systematic Review

Sarcopenic obesity (SO) is defined as co-occurrence of increased fat mass and sarcopenia and may predict adverse health outcomes in the pediatric population. However, the prevalence of SO and its association with adverse health outcomes have not been well defined in children and adolescents. We systematically reviewed data on the SO definition, prevalence, and adverse outcomes in the pediatric population. A total of 18 articles retrieved from PubMed or Web of Science databases were included. Overall, there was a wide heterogeneity in the methods and thresholds used to define SO. The prevalence of SO ranged from 5.66% to 69.7% in girls, with a range between 7.2% and 81.3% in boys. Of the 8 studies that evaluated outcomes related to SO, all showed a significant association of SO with cardiometabolic outcomes, non-alcoholic fatty liver disease (NAFLD) severity, inflammation, and mental health. In conclusion, this review found that SO is highly prevalent in children and adolescents and is associated with various adverse health outcomes. Findings of this review highlight the need for the development of a consensus regarding definition, standardized evaluation methods, and age and gender thresholds for SO for different ethnicities in the pediatric population. Further studies are needed to understand the relationship between obesity and sarcopenia and SO impact on adverse health outcomes in children and adolescents.

Official Position of the Brazilian Association of Bone Assessment and Metabolism (ABRASSO) on the evaluation of body composition by densitometry-part II (clinical aspects): interpretation, reporting, and special situations

OBJECTIVE

To present an updated and evidence-based guideline for the use of dual-energy x-ray absorptiometry (DXA) to assess body composition in clinical practice.

MATERIALS AND METHODS

This Official Position was developed by the Scientific Committee of the Brazilian Association of Bone Assessment and Metabolism (Associação Brasileira de Avaliação Óssea e Osteometabolismo, ABRASSO) and experts in the field who were invited to contribute to the preparation of this document. The authors searched current databases for relevant publications in the area of body composition assessment. In this second part of the Official Position, the authors discuss the interpretation and reporting of body composition parameters assessed by DXA and the use of DXA for body composition evaluation in special situations, including evaluation of children, persons with HIV, and animals.

CONCLUSION

This document offers recommendations for the use of DXA in body composition evaluation, including indications, interpretation, and applications, to serve as a guiding tool in clinical practice and research for health care professionals in Brazil.

The Relationship between Body Composition and Bone Mineral Density of Female Workers in A Unit of Tai’an

Objective. To explore the relationship between body composition and bone mineral density (BMD) of female workers in a university of Tai’an. Methods. This study randomly selected 90 female employees in a university of Tai’an. The body composition was monitored by body composition analyzer (inbody770), and the lumbar bone mineral density was monitored by dual energy X-ray absorptiometry (BMD model). The data were analyzed by SPSS 22.0 statistical software. Results. With the increasing of body mass index (BMI), BMD of female lumbar spines 1-4 (L1-4) increased gradually. Spearman correlation analysis showed that BMI, skeletal muscle mass, upper limb muscle mass, trunk muscle mass, lower limb muscle mass, and whole-body phase angle were positively correlated with L1-4BMD. Age was negatively correlated with L1-4BMD. Linear regression analysis showed that age was a negative factor of L1-4BMD, and skeletal muscle mass was a protective factor of abnormal bone mass, especially lower limb muscle mass. Conclusions. Lower limb muscle mass is a protective factor of female BMD. Strengthening physical exercise to improve lower limb muscle mass is conducive to the prevention of female osteoporosis.

Relationships of sex hormones with muscle mass and muscle strength in male adolescents at different stages of puberty

This study analysed the associations of sex steroids with fat-free mass (FFM) and handgrip strength in 641 Chinese boys. Serum total testosterone (TT) and oestradiol were measured by chemiluminescence immunoassay. Free testosterone (FT) and oestradiol were calculated. FFM and handgrip strength were measured by bioelectrical impedance analysis and a hand dynamometer, respectively. Generalised additive models and multiple linear regression were used to explore the relationships. A subgroup analysis was conducted in early-mid pubertal and late-post pubertal groups. Age, height, weight, physical activity, intake of dietary protein and/or stage of puberty were adjusted. TT and FT were positively related to FFM and handgrip strength, with a curvilinear relationship being detected for handgrip strength (p<0.050). This curvilinear relationship was only observed in the late-post pubertal group, suggesting a potential threshold effect (FT>11.99ng/dL, β = 1.275, p = 0.039). In the early-mid pubertal group, TT and/or FT were linearly or near-linearly related to FFM or handgrip strength (β = 0.003–0.271, p<0.050). The association between FT and FFM was stronger than that in the late-post pubertal group. This study found that serum T had different associations with muscle parameters in Chinese early-mid pubertal and late-post pubertal boys. In the late-post pubertal boys, serum T was curvilinearly related to muscle strength with a threshold effect and its link with muscle mass was weaker.

Physical exercise is associated with beneficial bone mineral density and body composition in young adults with childhood-onset inflammatory bowel disease

BACKGROUND

Patients with inflammatory bowel disease (IBD) have an increased risk of compromised bone mineral density (BMD) and body composition. There are limited data on the physical exercise (PE) habits of patients with childhood-onset IBD and on the associations between PE and BMD and body composition.

PATIENTS AND METHODS

In total, 72 young adults with childhood-onset IBD and 1341 normative young adult controls answered questionnaires regarding PE [hours/week (h/w)] in the last 12 months. BMD and body composition were measured with dual x-ray absorptiometry (DXA) and presented as age- and gender-adjusted Z-scores for BMD, skeletal muscle index (SMI, the weight of lean mass in arms and legs/m²), and percentage body fat (Fat %).

RESULTS

A total of 41 (57%) patients with IBD engaged in PE during the previous 12 months, as compared to 913 (68%) of the controls (p = .053). Sedentary patients had significantly lower median BMD, SMI, and Fat % Z-scores than the controls with corresponding PE habits (all p < .05). In contrast, highly active (>4 h/week) patients had total body BMD, SMI, and Fat % in the same range as the controls with corresponding PE levels (p = .151, p = .992, and p = .189, respectively), albeit with lower BMDs in the spine (p = .007) and femoral neck (p = .015). Using multiple regression analyses, a diagnosis of childhood-onset IBD was independently associated with inferior BMD and body composition, regardless of the amount of PE.

CONCLUSION

Physical exercise is associated with beneficial bone mineral density and body composition in patients with IBD despite the negative effects of the disease.

Interactions between Growth of Muscle and Stature: Mechanisms Involved and Their Nutritional Sensitivity to Dietary Protein: The Protein-Stat Revisited

Childhood growth and its sensitivity to dietary protein is reviewed within a Protein-Stat model of growth regulation. The coordination of growth of muscle and stature is a combination of genetic programming, and of two-way mechanical interactions involving the mechanotransduction of muscle growth through stretching by bone length growth, the core Protein-Stat feature, and the strengthening of bone through muscle contraction via the mechanostat. Thus, growth in bone length is the initiating event and this is always observed. Endocrine and cellular mechanisms of growth in stature are reviewed in terms of the growth hormone-insulin like growth factor-1 (GH-IGF-1) and thyroid axes and the sex hormones, which together mediate endochondral ossification in the growth plate and bone lengthening. Cellular mechanisms of muscle growth during development are then reviewed identifying (a) the difficulties posed by the need to maintain its ultrastructure during myofibre hypertrophy within the extracellular matrix and the concept of muscle as concentric "bags" allowing growth to be conceived as bag enlargement and filling, (b) the cellular and molecular mechanisms involved in the mechanotransduction of satellite and mesenchymal stromal cells, to enable both connective tissue remodelling and provision of new myonuclei to aid myofibre hypertrophy and (c) the implications of myofibre hypertrophy for protein turnover within the myonuclear domain. Experimental data from rodent and avian animal models illustrate likely changes in DNA domain size and protein turnover during developmental and stretch-induced muscle growth and between different muscle fibre types. Growth of muscle in male rats during adulthood suggests that "bag enlargement" is achieved mainly through the action of mesenchymal stromal cells. Current understanding of the nutritional regulation of protein deposition in muscle, deriving from experimental studies in animals and human adults, is reviewed, identifying regulation by amino acids, insulin and myofibre volume changes acting to increase both ribosomal capacity and efficiency of muscle protein synthesis via the mechanistic target of rapamycin complex 1 (mTORC1) and the phenomenon of a "bag-full" inhibitory signal has been identified in human skeletal muscle. The final section deals with the nutritional sensitivity of growth of muscle and stature to dietary protein in children. Growth in length/height as a function of dietary protein intake is described in the context of the breastfed child as the normative growth model, and the "Early Protein Hypothesis" linking high protein intakes in infancy to later adiposity. The extensive paediatric studies on serum IGF-1 and child growth are reviewed but their clinical relevance is of limited value for understanding growth regulation; a role in energy metabolism and homeostasis, acting with insulin to mediate adiposity, is probably more important. Information on the influence of dietary protein on muscle mass per se as opposed to lean body mass is limited but suggests that increased protein intake in children is unable to promote muscle growth in excess of that linked to genotypic growth in length/height. One possible exception is milk protein intake, which cohort and cross-cultural studies suggest can increase height and associated muscle growth, although such effects have yet to be demonstrated by randomised controlled trials.

Sarcopenia in children and adolescents with chronic liver disease

OBJECTIVE

To investigate the occurrence of sarcopenia in children and adolescents with chronic liver disease.

METHODS

A series of cases, with patients aged 6-19 years of both genders, who were treated in Liver Outpatient Clinics. Weight, height, muscle strength (assessed by manual grip strength), and muscle mass (estimated through dual-energy X-ray absorptiometry) were measured. Sarcopenia was diagnosed based on the simultaneous presence of muscle mass and muscle strength déficits, defined as the values below the mean for muscle mass and strength of the studied population, according to gender. A descriptive analysis (mean and standard deviation) was performed, and the difference of means was calculated by Student's t-test.

RESULTS

A total of 85 patients were studied, mostly females (64.7%), with a mean age of 11.7 (SD=3.4) years. Sarcopenia was identified in 40% of the patients. Muscle strength déficit was found in 54.1% of the subjects, and 50.6% showed muscle mass déficit. The mean muscle mass for males was higher than that for females (6.07; SD=1.22kg/m²vs. 5.42; SD=1.10kg/m²; p=0.016). However, there was no significant difference in sex-related muscle strength (male=0.85; SD=0.52kgf/kgm² and female=0.68; SD=0.30kgf/kgm²; p=0.113).

CONCLUSION

The research findings identified that sarcopenia is a condition found in pediatric patients treated at a public referral institution for chronic liver disease.

Sex-specific and age-specific characteristics of body composition and its effect on bone mineral density in adults in southern China: a cross-sectional study

OBJECTIVES

This study was an attempt to investigate the variation trend of body composition with ageing and explore the association between regional body composition and bone mineral density (BMD).

DESIGN

Cross-sectional study.

SETTING AND PARTICIPANTS

A total of 5749 healthy adults aged 20-95 years was recruited from 2004 to 2017.

PRIMARY OUTCOME MEASURES

Whole-body lean mass (LM), fat mass (FM), android FM, gynoid FM, appendicular lean mass (ALM) and BMD in the lumbar spine, femoral neck and total hip were obtained by dual-energy X-ray absorptiometry (DXA). The android/gynoid fat mass ratio (A/G FMR) based on DXA scan was calculated as an indicator of adipose distribution. Pearson correlation and multiple linear regression analyses were used to determine the associations between body composition, adipose distribution, and BMD of each skeletal site.

RESULTS

Whole-body FM, percentage of whole-body FM, Android FM and A/G FMR consistently increased with age in both genders, especially in women, and ALM began to decrease in the fifth decade for both men and women. In multivariable linear regression models with age, body mass index, A/G FMR and ALM as predictor variables, ALM was associated with the most BMD variance of all skeletal sites in men (standard β ranged from 0.207 to 0.405, p<0.001), although not the largest but still a positive predictor of BMD in women (standard β ranged from 0.074 to 0.186, p<0.05). A/G FMR was an inverse predictor of BMD at all skeletal sites for women (standard β ranged from -249 to -0.052, p<0.01) but not in men.

CONCLUSIONS

In this large cohort of Chinese adults, ALM had a strong positive association with BMD in both genders. A/G FMR as an indicator of central adipose accumulation was inversely associated with BMD in women but not in men.

Quantification of skeletal muscle mass: sarcopenia as a marker of overall health in children and adults

Sarcopenia is defined as the loss of muscle mass or function and has been associated with increased morbidity and mortality in a variety of diseased populations. Sarcopenia results from a higher rate of muscle protein degradation compared to protein synthesis and is an important marker of metabolic status related to nutrition and physical activity. The diagnosis of sarcopenia is accomplished by clinical assessment demonstrating decreased muscle function and radiographic confirmation of decreased muscle mass, via dual X-ray absorptiometry, bioelectric impedance or cross-sectional imaging with CT or MRI. However, normative data for skeletal muscle mass are lacking, especially for children and young adults. Additionally, studies of skeletal muscle mass by cross-sectional imaging in children are scarce. Here, we review the concept of sarcopenia with an emphasis on its relevance in the pediatric population.

Lean mass reference curves in adolescents using dual-energy x-ray absorptiometry (DXA)

The body composition phenotype of low lean mass (LM) has been associated with metabolic disorders and impaired physical functioning in the pediatric population. Abnormalities in body composition may be identified using reference curves; however, no reference data on LM is available for Brazilian adolescents. The purpose of this study was to present reference data, including percentile curves, of whole body LM, lean mass index (LMI), appendicular lean mass (ALM), and fat mass for Southern Brazilian adolescents. This was a cross-sectional study of adolescents aged 12–17 years from a southern region in Brazil, who had body composition assessed using dual energy x-ray absorptiometry (DXA). Percentile values and reference curves employing the Lambda, Mu and Sigma method (LMS) were computed for LM, LMI (lean mass/height²), ALM and fat mass. Data on 541 adolescents (68.6% boys) was included. Sex differences in growth trajectories were observed for absolute and adjusted LM, with boys presenting greater LM quantity with advancing ages than girls (66.9% and 17.4% difference between the ages of 12 and 17 for boys and girls, respectively). The values corresponding to the lowest percentile (3^rd) of LMI ranged between 10.63 to 13.93 kg/m² in boys and 11.13 to 12.03 kg/m² among girls aged 12–17 years. This study established the first LM, LMI, and ALM reference curves in Southern Brazilian adolescents, which can potentially be used in association with functional measures to identify LM abnormalities during growth.

Altered body composition profiles in young adults with childhood-onset inflammatory bowel disease

Background: Patients with inflammatory bowel disease (IBD) often develop alterations in body composition in terms of their proportions of lean mass and fat mass, as well as reduced bone mineral density (BMD). However, there are limited data on the skeletal muscle index (SMI) and percentage fat (fat %) for young adults with childhood-onset IBD. Our aim was to investigate the body compositions of these patients, with the focus on SMI and fat %.Methods: Body composition was estimated by dual x-ray absorptiometry for 94 young adults with childhood-onset IBD aged 18-27 years, 65 of whom had ulcerative colitis. The Z-scores for SMI, fat %, and BMD were calculated using the normative data from 1,289 individuals with corresponding age. Based on the SMI and fat % Z-scores, each patient was classified as having a body composition profile that was: (i) normal; (ii) obese (fat % Z-score >1); (iii) myopenic (SMI Z-score < -1); or (iv) myopenic-obese.Results: A higher proportion of young adults with childhood-onset IBD had a body composition profile classified as myopenic (24%) or myopenic-obese (9%), as compared to the controls (myopenic [16%, p = .016]; myopenic-obese [2%, p = .002]). Patients with the myopenic or myopenic-obese profile had significantly lower total body BMD Z-scores (-1.3 ± 0.7 and -1.4 ± 0.9, respectively) than patients with the normal profile (-0.2 ± 1.1; p < .001 and p = .004, respectively). Diagnosis of IBD in childhood represented an additional risk for low BMD, regardless of SMI Z-score.Conclusion: Young adults with childhood-onset IBD have a high risk for having altered body composition traits.SummaryYoung adults with childhood-onset IBD carry a high risk for altered body composition traits. The myopenic and myopenic-obese body composition profiles were more frequently observed in patients with IBD than controls, and these profiles were strongly associated with low BMD.

Sex differences in the longitudinal associations between body composition and bone stiffness index in European children and adolescents

Fat mass (FM) and fat free mass (FFM) may influence bone health differentially. However, existing evidences on associations between FM, FFM and bone health are inconsistent and vary according to sex and maturity. The present study aims to evaluate longitudinal associations between FM, FFM and bone stiffness index (SI) among European children and adolescents with 6 years follow-up. A sample of 2468 children from the IDEFICS/I.Family was included, with repeated measurements of SI using calcaneal quantitative ultrasound, body composition using skinfold thickness, sedentary behaviors and physical activity using self-administrated questionnaires. Regression coefficients (β) and 99%-confidence intervals (99% CI) were calculated by sex-specified generalized linear mixed effects models to analyze the longitudinal associations between FM and FFM z-scores (zFM and zFFM) and SI percentiles, and to explore the possible interactions between zFM, zFFM and maturity. Baseline zFFM was observed to predict the change in SI percentiles in both boys (β = 4.57, 99% CI: 1.36, 7.78) and girls (β = 3.42, 99% CI: 0.05, 6.79) after 2 years. Moreover, baseline zFFM (β = 8.72, 99% CI: 3.18, 14.27 in boys and β = 5.89, 99% CI: 0.34, 11.44 in girls) and the change in zFFM (β = 6.58, 99% CI: 0.83, 12.34 in boys and β = 4.81, 99% CI: -0.41, 10.02 in girls) were positively associated with the change in SI percentiles after 6 years. In contrast, a negative association was observed between the change in zFM and SI percentiles in boys after 6 years (β = -3.70, 99% CI: -6.99, -0.42). Besides, an interaction was observed between the change in zFM and menarche on the change in SI percentiles in girls at 6 years follow-up (p = .009), suggesting a negative association before menarche while a positive association after menarche. Our findings support the existing evidences for a positive relationship between FFM and SI during growth. Furthermore, long-term FM gain was inversely associated with SI in boys, whereas opposing associations were observed across menarche in girls.

Development of a Computational Model to Predict Excess Body Fat in Adolescents through Low Cost Variables

BACKGROUND

Excess body fat has been growing alarmingly among adolescents, especially in low income and middle income countries where access to health services is scarce. Currently, the main method for assessing overweight in adolescents is the body mass index, but its use is criticized for its low sensitivity and high specificity, which may lead to a late diagnosis of comorbidities associated with excess body fat, such as cardiovascular diseases. Thus, the aim of this study was to develop a computational model using linear regression to predict obesity in adolescents and compare it with commonly used anthropometric methods. To improve the performance of our model, we estimated the percentage of fat and then classified the nutritional status of these adolescents.

METHODS

The model was developed using easily measurable socio-demographic and clinical variables from a database of 772 adolescents of both genders, aged 10-19 years. The predictive performance was evaluated by the following metrics: accuracy, sensitivity, specificity, and area under ROC curve. The performance of the method was compared to the anthropometric parameters: body mass index and waist-to-height ratio.

RESULTS

Our model showed a high correlation (R = 0.80) with the body fat percentage value obtained through bioimpedance. In addition, regarding discrimination, our model obtained better results compared to BMI and WHtR: AUROC = 0.80, 0.64, and 0.55, respectively. It also presented a high sensitivity of 92% and low false negative rate (6%), while BMI and WHtR showed low sensitivity (27% and 9.9%) and a high false negative rate (65% and 53%), respectively.

CONCLUSIONS

The computational model of this study obtained a better performance in the evaluation of excess body fat in adolescents, compared to the usual anthropometric indicators presenting itself as a low cost alternative for screening obesity in adolescents living in Brazilian regions where financial resources are scarce.

Differences in the relation between bone mineral content and lean body mass according to gender and reproductive status by age ranges

The present study aims: (1) to explore the influence of lean mass (LM) on bone mineral content (BMC), (2) to investigate the pubertal influences on the BMC-LM relation, and (3) to perform Z-score charts of BMC-LM relation, stratified by gender and reproductive status categorized by age ranges. A cross-sectional analysis was conducted using 4001 healthy subjects between 7 and 90 years participating in the Health Workers Cohort Study. Of these, 720 participants were ≤ 19 years, 2417 were women ≥ 20 years, and 864 were men ≥ 20 years. Using Dual X-ray absorptiometry (DXA), we measured BMC and LM. Participants' pubertal development was assessed according to Tanner's stage scale. To describe BMC-LM relation, simple correlation coefficients were computed. To produce best-fit equations, an ANOVA test was conducted. Z-score graphs for the BMC-LM relation were obtained. In general, the BMC-LM correlations were linear and highly significant. For boys, curves were virtually parallel, with similar intercepts and a progressive displacement of values toward the upper-right region of the graph, for each Tanner subgroup. For girls, curves for Tanner 1-2 and 4-5 stages were parallel; but, in girls Tanner 4-5, the intercepts were significantly higher by about +300-400 g of BMC (P < 0.001). For postmenopausal women, the curve was parallel to that for the premenopausal but showed a lower intercept (P < 0.001). We provide DXA reference data on a well-characterized cohort of 4001 healthy subjects. These reference curves provide a reference value for the assessment and monitoring of bone health in all age groups included in the present study.

Low muscle mass and strength in pediatrics patients: Why should we care?

Skeletal muscle plays major roles in metabolism and overall health across the lifecycle. Emerging evidence indicates that prenatal (maternal diet during pregnancy and genetic defects) and postnatal factors (physical activity, hormones, dietary protein, and obesity) influence muscle mass acquisition and strength early in life. As a consequence, low muscle mass and strength contributes to several adverse health outcomes during childhood. Specifically, studies demonstrated inverse associations of muscle mass and strength to single and clustered metabolic risk factors. The literature also consistently reports that low muscle mass and strength are associated with reduced bone parameters during growth, increasing the risk of osteoporosis in old age. Furthermore, muscle mass gains are associated with improved neurodevelopment in the first years of life. Given these negative implications of low muscle mass and strength on health, it is crucial to track muscle mass and strength development from childhood to adolescence. Several body composition techniques are currently available for estimation of muscle mass, all with unique advantages and disadvantages. The value of ultrasound as a technique to measure muscle mass is emerging in pediatric research with potential for translating the research findings to clinical settings. For the assessment of muscle strength, the handgrip strength test has been widely employed but without a standardized protocol. Although further research is needed to define normative data and cut points for the low muscle mass and strength phenotype, the use of such non-invasive medical monitoring is a promising strategy to identify early abnormalities and prevent low muscle mass in adulthood.

Analysis of bone mass and its relationship with body composition in school-aged children and adolescents based on stage of puberty and site specificity: A retrospective case-control study

The aim of this study was to better understand the relationship of bone mass with body composition based on different stages of puberty and to illuminate the contribution of site-specific fat mass and lean mass (FM and LM) compared with bone mass in school-aged children and adolescents in Chongqing, China.A total of 1179 healthy subjects of both sexes were recruited. Bone mineral content (BMC), bone mineral density (BMD), bone area, and both FM and LM were measured by dual-energy X-ray absorptiometry (DXA). The fat mass and lean mass indexes (FMI and LMI, respectively) were calculated as the FM (kg) and LM (kg) divided by the height in meters squared, respectively.Most of the bone mass indicators were significantly higher for postpubertal boys than for girls at the same stage (P < .001). The proportion of subjects with normal bone mass increased, while the proportion of subjects with osteopenia and osteoporosis decreased with increased body weight regardless of gender and puberty stage (P < .01). FM and LM were significantly positively related to bone mass regardless of gender and puberty stage (P < .0001). FMI and LMI were significantly positively related to bone mass in most conditions (P < .05 and P < .0001, respectively). Four components of the FM and LM were linearly and significantly associated with BMD and BMC for TB and TBHL. Among them, the head fat mass and head lean mass showed the greatest statistical contribution.In the process of assessing bone status, we recommend measuring fat and lean masses, including the fat and lean masses of the head.

Muscle Mass in Children and Adolescents: Proposed Equations and Reference Values for Assessment

Objectives: The goal of this study was to develop regression equations to estimate LM with anthropometric variables and to propose percentiles for evaluating by age and sex. Methods: A cross sectional study was conducted with 2,182 Chilean students (1,347 males and 835 females). Ages ranged from 5.0 to 17.9 years old. A total body scan was carried out with the double energy X-ray anthropometry (DXA) to examine and measure lean muscle mass of the entire body. Weight, height, and the circumference of the relaxed right arm were also measured. Results: Four anthropometric equations were generated to predict lean mass for both sexes (R ² = 83-88%, SEE = 3.7-5.0%, precision = 0.90-0.93, and accuracy = 0.99). The Lambda-mu-sigma method was used to obtain the sex-specific and age-specific percentile curves of lean mass (p3, p5, p10, p15, p25, p50, p75, p85, p90, p95, and p97). Conclusion: The four proposed equations were acceptable in terms of precision and accuracy to estimate lean mass in children and adolescents. The percentiles were created by means of anthropometric equations and real values for DXA. These are fundamental tools for monitoring LM in Chilean children and adolescents of both sexes.