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Single- and multifrequency bioelectrical impedance analysis (BIA) has gained popularity as a tool to assess body composition and health status of children and adolescents, but many questions and misconceptions remain. This review addresses pressing issues researchers and health care providers may encounter when using BIA in the young population. The importance of choosing population-specific and device-specific equations to estimate body composition as well as the use of BIA in longitudinal analyses are discussed. When specific equations are not available, raw bioimpedance values (i.e., resistance, reactance, and impedance) can be used to compute bioimpedance parameters, such as phase angle, impedance ratio, and bioelectrical impedance vector analysis. As interpreting these parameters is challenging, suggestions are provided on the use of reference data, cut-off points, and adjustment factors. Furthermore, unsolved technical and analytical issues are listed. Based on existing issues and potential for future development, a greater interaction between industry and academic researchers to improve the validity of BIA measurements among children and adolescents across their developmental stages is encouraged.

COVID-19 negatively impacts several organs and systems weeks or months after initial diagnosis. Skeletal muscle can be affected, leading to fatigue, lower mobility, weakness, and poor physical performance. Older adults are at increased risk of developing musculoskeletal symptoms during long COVID. Systemic inflammation, physical inactivity, and poor nutritional status are some of the mechanisms leading to muscle dysfunction in individuals with long COVID. Current evidence suggests that long COVID negatively impacts body composition, muscle function, and quality of life. Muscle mass and function assessments can contribute toward the identification, diagnosis, and management of poor muscle health resulting from long COVID.

The emerging role of a microbiota-gut-brain axis in autism spectrum disorder (ASD) suggests that modulating gut microbial composition may offer a tractable approach to addressing the lifelong challenges of ASD. The aim of this systematic review was to provide an overview and critically evaluate the current evidence on the efficacy and safety of probiotic, prebiotic, synbiotic, and fecal microbiota transplantation therapies for core and co-occurring behavioral symptoms in individuals with ASD. Comprehensive searches of MEDLINE, EMBASE, Scopus, Web of Science Core Collection, Cochrane Library, and Google Scholar were performed from inception to March 5, 2020, and two update searches were completed on October 25, 2020, and April 22, 2021, respectively. A total of 4306 publications were identified, of which 14 articles met the inclusion criteria. Data were extracted independently by two reviewers using a preconstructed form. Results of probiotic studies do not confirm the supposed beneficial effect of probiotics on ASD, whereas prebiotics and synbiotic combinations appear to be efficacious in selective behavioral symptoms. Evidence of the efficacy of fecal microbiota transplantation in ASD is still scarce but supports further research. Overall, the current evidence base to suggest beneficial effects of these modalities in ASD is limited and inconclusive. More clinical trials are currently looking at the use of microbial-based therapies in ASD. With a robust double-blind randomized controlled protocol to investigate the efficacy, these trials should provide significant and definitive results. LAY SUMMARY: There is a link between altered gut bacteria and autism spectrum disorder. Some people believe that modulating bacterial composition in the gut may help reduce autism symptoms, but evidence from human studies suggesting beneficial effects of probiotic, prebiotic, and combination thereof as well as fecal transplants in autism spectrum disorder is limited and inconclusive. Current data should not encourage use of these modalities. Further clinical studies are needed.

Background Accumulating evidence suggests that the metabolic effects of metformin and fermentable fibers are mediated, in part, through diverging or overlapping effects on the composition and metabolic functions of the gut microbiome. Pre-clinical animal models have established that the addition of fiber to metformin monotherapy improves glucose tolerance. However, possible synergistic effects of combination therapy (metformin plus fiber) have not been investigated in humans. Moreover, the underlying mechanisms of synergy have yet to be elucidated. The aim of this study is to compare in adolescents with obesity the metabolic effects of metformin and fermentable fibers in combination with those of metformin or fiber alone. We will also determine if therapeutic responses correlate with compositional and functional features of the gut microbiome. Methods This is a parallel three-armed, double-blinded, randomized controlled trial. Adolescents (aged 12–18 years) with obesity, insulin resistance (IR), and a family history of type 2 diabetes mellitus (T2DM) will receive either metformin (850 mg p.o. twice/day), fermentable fibers (35 g/day), or a combination of metformin plus fiber for 12 months. Participants will be seen at baseline, 3, 6, and 12 months, with a phone follow-up at 1 and 9 months. Primary and secondary outcomes will be assessed at baseline, 6, and 12 months. The primary outcome is change in IR estimated by homeostatic model assessment of IR; key secondary outcomes include changes in the Matsuda index, oral disposition index, body mass index z-score, and fat mass to fat-free mass ratio. To gain mechanistic insight, endpoints that reflect host-microbiota interactions will also be assessed: obesity-related immune, metabolic, and satiety markers; humoral metabolites; and fecal microbiota composition, short-chain fatty acids, and bile acids. Discussion This study will compare the potential metabolic benefits of fiber with those of metformin in adolescents with obesity, determine if metformin and fiber act synergistically to improve IR, and elucidate whether the metabolic benefits of metformin and fiber associate with changes in fecal microbiota composition and the output of health-related metabolites. This study will provide insight into the potential role of the gut microbiome as a target for enhancing the therapeutic efficacy of emerging treatments for T2DM prevention. Trial registration ClinicalTrials.gov NCT04578652. Registered on 8 October 2020.

Computed tomography (CT) is gaining increased recognition in the assessment of body composition in lung transplant (LTx) candidates as a prognostic marker of post-transplant outcomes. This systematic review was conducted to describe the methodology of CT measures of body composition used in LTx patients and its association with post-transplant outcomes. Six databases were searched (inception-April 2020) for studies of adult LTx patients with thoracic or abdominal CT measures [muscle cross-sectional area (CSA) and/or adiposity]. Thirteen articles were included with 1911 LTx candidates, 58% males, mean age range (48-61 years) and body mass index of 21.0-26.1 kg/m2 . Several methods were utilized using thoracic or abdominal CT scans to assess skeletal muscle (n = 11) and adiposity (n = 4) at various anatomic locations (carina, thoracic, and lumbar vertebrae), differing muscle groups, and adipose tissue compartments. Low muscle mass was associated with adverse outcomes in 6/11 studies, including longer mechanical ventilation days (n = 2), intensive care (n = 2) and hospital stay (n = 2), and mortality (n = 4). Greater subcutaneous and mediastinal fat were associated with increased risk of primary graft dysfunction (n = 2), but implications of adiposity on survival were variable across four studies. Further standardization of CT body composition assessments is needed to assess the prognostic utility of these measures on LTx outcomes.

The incretin hormone glucagon-like peptide-1 (GLP-1) has received enormous attention during the past three decades as a therapeutic target for the treatment of obesity and type 2 diabetes. Continuous improvement of the pharmacokinetic profile of GLP-1R agonists, starting from native hormone with a half-life of ~2–3 min to the development of twice daily, daily and even once-weekly drugs highlight the pharmaceutical evolution of GLP-1-based medicines. In contrast to GLP-1, the incretin hormone glucose-dependent insulinotropic polypeptide (GIP) received little attention as a pharmacological target, because of conflicting observations that argue activation or inhibition of the GIP receptor (GIPR) provides beneficial effects on systemic metabolism. Interest in GIPR agonism for the treatment of obesity and diabetes was recently propelled by the clinical success of unimolecular dual-agonists targeting the receptors for GIP and GLP-1, with reported significantly improved body weight and glucose control in patients with obesity and type II diabetes. Here we review the biology and pharmacology of GLP-1 and GIP and discuss recent advances in incretin-based pharmacotherapies.

The pediatric relative fat mass (RFM) has been recently presented and validated as an index for estimating percentage body fat (%BF) in North American children and adolescents. Similar to body mass index (BMI) and tri-ponderal mass index (TMI), RFM uses anthropometric measures (i.e., weight, height and waist circumference) to estimate body composition. The primary purpose of this study was to validate the newly developed RFM equation for %BF prediction in Southern Brazilian adolescents; as secondary objective, we compared %BF estimation from BMI- and TMI-derived equations. A total of 631 individuals (434 boys) aged 11 to 18 were analyzed. Bland–Altman analyses were used to determine concordance between predicted equations and %BF measured by DXA; results are presented using mean difference (i.e., bias) and standard deviation. Sensitivity and specificity were calculated for %BF percentile classifications. RFM underestimated %BF in 65.2% of boys (− 4.3 ± 2.8%) and 84.8% of girls (− 5.3 ± 2.7%). In contrast, TMI overestimated %BF in 62.9% of boys (4.0 ± 2.9%) and 56.3% (3.5 ± 3.0%) of girls. The performance of BMI showed mixed results; %BF was overestimated in 68.4% of boys (5.0 ± 4.0%) and underestimated in 67.5% of girls (− 3.9 ± 2.6%), all p

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.

Individuals with cancer may be motivated to make lifestyle changes and informed dietary choices, but are exposed to conflicting and erroneous nutrition information, particularly from online and social media sources. Changes to dietary choices that stem from a diagnosis of cancer are not fully understood. Thus, we conducted a narrative review to summarize the literature focused on dietary choices after a cancer diagnosis, and highlighted influential factors. Postdiagnosis dietary changes have been studied primarily in female patients with breast cancer in European countries. Reported changes typically included decreased red and processed meat intake and increased consumption of fruits and vegetables. These changes align with the recommendations for cancer prevention but were implemented after diagnosis, and may not meet nutrition guidelines for patients with cancer. Age and time since diagnosis were among the influential factors that affected these postdiagnosis changes. Data on dietary changes implemented after a diagnosis of varying cancer types in the North American population are lacking, and would provide practitioners with an enhanced understanding of patient information needs and reasons for dietary choices.

Single- and multifrequency bioelectrical impedance analysis (BIA) has gained popularity as a tool to assess body composition and health status of children and adolescents, but many questions and misconceptions remain. This review addresses pressing issues researchers and health care providers may encounter when using BIA in the young population. The importance of choosing population-specific and device-specific equations to estimate body composition as well as the use of BIA in longitudinal analyses are discussed. When specific equations are not available, raw bioimpedance values (i.e., resistance, reactance, and impedance) can be used to compute bioimpedance parameters, such as phase angle, impedance ratio, and bioelectrical impedance vector analysis. As interpreting these parameters is challenging, suggestions are provided on the use of reference data, cut-off points, and adjustment factors. Furthermore, unsolved technical and analytical issues are listed. Based on existing issues and potential for future development, a greater interaction between industry and academic researchers to improve the validity of BIA measurements among children and adolescents across their developmental stages is encouraged.

Background Computed tomography (CT) is commonly utilized in chronic obstructive pulmonary disease (COPD) for lung cancer screening and emphysema characterization. Computed tomography-morphometric analysis of body composition (muscle mass and adiposity) has gained increased recognition as a marker of disease severity and prognosis. This systematic review aimed to describe the CT-methodology used to assess body composition and identify the association of body composition measures and disease severity, health-related quality of life (HRQL), cardiometabolic risk factors, respiratory exacerbations, and survival in patients with COPD. Methods Six databases were searched (inception-September 2021) for studies evaluating adult COPD patients using thoracic or abdominal CT-muscle or adiposity body composition measures. The systematic review was conducted in accordance with the PRISMA guidelines. Results Twenty eight articles were included with 15,431 COPD patients, across all GOLD stages with 77% males, age range (mean/median 59–78 years), and BMI range 19.8–29.3 kg/m2. There was heterogeneity in assessment of muscle mass and adiposity using thoracic ( n = 22) and abdominal ( n = 8) CT-scans, capturing different muscle groups, anatomic locations, and adiposity compartments (visceral, subcutaneous, and epicardial). Low muscle mass and increased adiposity were associated with increased COPD severity measures (lung function, exercise capacity, dyspnea) and lower HRQL, but were not consistent across studies. Increased visceral adiposity ( n = 6) was associated with cardiovascular disease or risk factors (hypertension, hyperlipidemia, and diabetes). Low muscle CSA was prognostic of respiratory exacerbations or mortality in three of six studies, whereas the relationship with increased intermuscular adiposity and greater mortality was only observed in one of three studies. Conclusion There was significant variability in CT-body composition measures. In several studies, low muscle mass was associated with increased disease severity and lower HRQL, whereas adiposity with cardiovascular disease/risk factors. Given the heterogeneity in body composition measures and clinical outcomes, the prognostic utility of CT-body composition in COPD requires further study.

Bone mineral density (BMD) is of concern in Prader-Willi syndrome (PWS). This study compared responses to a physical activity intervention in bone parameters and remodeling markers in youth with PWS (n = 45) and youth with non-syndromic obesity (NSO, n = 66). Measurements occurred at baseline (PRE) and after 24 weeks (POST) of a home-based active games intervention with strengthening and jumping exercises (intervention group = I) or after a no-intervention period (control group = C). Dual x-ray absorptiometry scans of the hip and lumbar spine (L1-L4) determined BMD and bone mineral content (BMC). Bone markers included fasting bone-specific alkaline phosphatase (BAP) and C-terminal telopeptide of type I collagen (CTx). Both I and C groups increased their hip BMD and BMC (p &lt, 0.001). Youth with PWS-I increased their spine BMC from PRE to POST (p &lt, 0.001) but not youth with PWS-C (p = 1.000). Youth with NSO (I and C) increased their spine BMC between PRE and POST (all p &lt, 0.001). Youth with PWS showed lower BAP (108.28 &plusmn, 9.19 vs. 139.07 &plusmn, 6.41 U/L, p = 0.006) and similar CTx (2.07 &plusmn, 0.11 vs.1.84 &plusmn, 0.14 ng/dL, p = 0.193) than those with NSO regardless of time. Likely, the novelty of the intervention exercises for those with PWS contributed to gains in spine BMC beyond growth. Bone remodeling markers were unaltered by the intervention.

Summary Cancer-associated cachexia is a complex metabolic syndrome characterized by weight loss and systemic inflammation. Muscle loss and fatty infiltration into muscle are associated with poor prognosis in cancer patients. Skeletal muscle secretes myokines, factors with autocrine, paracrine and/or endocrine action, which may be modified by or play a role in cachexia. This study examined myokine content in the plasma, skeletal muscle and tumor homogenates from treatment-naive patients with gastric or colorectal stages I-IV cancer with cachexia (CC, N = 62), or not (weight stable cancer, WSC, N = 32). Myostatin, interleukin (IL) 15, follistatin-like protein 1 (FSTL-1), fatty acid binding protein 3 (FABP3), irisin and brain-derived neurotrophic factor (BDNF) protein content in samples was measured with Multiplex technology; body composition and muscle lipid infiltration were evaluated in computed tomography, and quantification of triacylglycerol (TAG) in the skeletal muscle. Cachectic patients presented lower muscle FSTL-1 expression (p = 0.047), higher FABP3 plasma content (p = 0.0301) and higher tumor tissue expression of FABP3 (p = 0.0182), IL-15 (p = 0.007) and irisin (p = 0.0110), compared to WSC. Neither muscle TAG content, nor muscle attenuation were different between weight stable and cachectic patients. Lumbar adipose tissue (AT) index, visceral AT index and subcutaneous AT index were lower in CC (p = 0.0149, p = 0.0455 and p = 0.0087, respectively), who also presented lower muscularity in the cohort (69.2% of patients; p = 0.0301), compared to WSC. The results indicate the myokine profile in skeletal muscle, plasma and tumor is impacted by cachexia. These findings show that myokines eventually affecting muscle wasting may not solely derive from the muscle itself (as the tumor also may contribute to the systemic scenario), and put forward new perspectives on cachexia treatment targeting myokines and associated receptors and pathways.

In early childhood, individuals with Prader-Willi syndrome (PWS) experience excess weight gain and severe hyperphagia with food compulsivity, which often leads to early onset morbid obesity. Effective treatments for appetite suppression and weight control are currently unavailable for PWS. Our aim to further understand the pathogenesis of PWS led us to carry out a comprehensive search of the current and emerging therapies for managing hyperphagia and extreme weight gain in PWS. A literature search was performed using PubMed and the following keywords: "PWS" AND "therapy" OR "[drug name]"; reference lists, pharmaceutical websites, and the ClinicalTrials.gov registry were also reviewed. Articles presenting data from current standard treatments in PWS and also clinical trials of pharmacological agents in the pipeline were selected. Current standard treatments include dietary restriction/modifications, exercise, and growth hormone replacement, which appear to have limited efficacy for appetite and weight control in patients with PWS. The long-term safety and effectiveness of bariatric surgery in PWS remains unknown. However, many promising pharmacotherapies are in development and, if approved, will bring much needed choices into the PWS pharmacological armamentarium. With the progress that is currently being made in our understanding of PWS, an effective treatment may not be far off.

The pediatric relative fat mass (RFM) has been recently presented and validated as an index for estimating percentage body fat (%BF) in North American children and adolescents. Similar to body mass index (BMI) and tri-ponderal mass index (TMI), RFM uses anthropometric measures (i.e., weight, height and waist circumference) to estimate body composition. The primary purpose of this study was to validate the newly developed RFM equation for %BF prediction in Southern Brazilian adolescents; as secondary objective, we compared %BF estimation from BMI- and TMI-derived equations.A total of 631 individuals (434 boys) aged 11 to 18 were analyzed. Bland-Altman analyses were used to determine concordance between predicted equations and %BF measured by DXA; results are presented using mean difference (i.e., bias) and standard deviation. Sensitivity and specificity were calculated for %BF percentile classifications.RFM underestimated %BF in 65.2% of boys (- 4.3 ± 2.8%) and 84.8% of girls (- 5.3 ± 2.7%). In contrast, TMI overestimated %BF in 62.9% of boys (4.0 ± 2.9%) and 56.3% (3.5 ± 3.0%) of girls. The performance of BMI showed mixed results; %BF was overestimated in 68.4% of boys (5.0 ± 4.0%) and underestimated in 67.5% of girls (- 3.9 ± 2.6%), all p 0.001. Although, RFM had the highest specificity for %BF percentile classifications, sensitivity was low and inferior to BMI and TMI.TMI was superior to RFM and BMI in predicting %BF in Southern Brazilian adolescents. Using RFM, BMI or TMI equations for %BF prediction without a population-specific correction factor may lead to incorrect interpretations. We suggest that correction factors should be investigated to improve the accuracy of these surrogate indices for body composition assessment.Level V, cross sectional descriptive study.

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 (3rd) 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.

There is growing interest in evaluating body composition using routine clinical computed tomography (CT) scans; however, the validity of this technique in lung transplant patients has not been described. The study objectives were to determine the reliability of measuring fat compartments from thoracic CT and evaluate the validity of muscle and fat cross-sectional area (CSA) from thoracic CT by comparing to bioelectrical impedance analysis (BIA). Thoracic CT scans from lung transplant assessments were obtained for analysis. Total thoracic muscle CSA, pectoral muscle CSA, subcutaneous adipose tissue (SAT), and mediastinal adipose tissue (MAT) were manually segmented by two independent raters. Reliability was analysed using intra-class correlation coefficient (ICC). Correlations were determined between CT measures with fat-free mass index (FFMI), body fat mass index (BFMI) and per cent body fat (%BF) from BIA; and anthropometrics [body mass index (BMI) and waist circumference (WC)]. High inter- and intra-rater reliability were found for SAT and MAT (ICCs = 0.99). Pectoral and total muscle CSA were correlated with FFMI (r = .41, p = .003 and r = .57, p < .001, respectively). SAT was associated with whole-body fat from BIA and with BMI and WC (r = .61 to .80, p < .001). MAT was associated with BMI (r = .58, p < .001) and WC (r = .61, p < .001). This study supports the reliability and validity of using thoracic CT to measure muscle and fat. Future studies are needed to investigate whether these CT-based measures are predictive of clinical and post-transplant outcomes in advanced lung disease.

BACKGROUND: Dietary DHA intake among US toddlers is low. Healthy physical growth is an important objective for the clinical care of children born preterm. OBJECTIVES: The aim of the trial was to examine the effects of supplementing toddlers born preterm with DHA and arachidonic acid (AA) for 180 d on growth and adiposity. METHODS: Omega Tots, a randomized placebo-controlled trial, was conducted between April 2012 and March 2017. Children born at

Skeletal muscle is recognized as a tissue with high metabolic capacity given its key roles in glucose and lipid metabolism. Although low muscle mass has been associated with metabolic disorders in adults, it is not clear if this body composition phenotype is related to metabolic health status earlier in life. In this review, we aim to clarify whether having low muscle mass is associated with increased risk of metabolic dysregulation in the pediatric population. Fifteen original articles investigating the relationship between body composition measures of muscle mass and single or clustered metabolic risk factors in children and adolescents were critically evaluated. Despite a growing body of evidence supporting low muscle mass as a risk factor for metabolic health in children and adolescents, conflicting associations were reported. Differences in body composition techniques, muscle mass indices, and clinical methods used to assess metabolic biomarkers may have contributed to a lack of a consistent conclusion. Moreover, most studies did not control for potential biological and lifestyle confounders. Future studies using precise, reproducible techniques to evaluate body composition and metabolic biomarkers are required to determine the implications of low muscle mass on metabolic health during childhood and adolescence.

The roles of obestatin and adropin in paediatric obesity are poorly understood. We compared obestatin and adropin concentrations in younger (n = 21) and older children (n = 14) with Prader-Willi syndrome (PWS) and age and BMI-z-matched controls (n = 31). Fasting plasma obestatin and adropin were higher in younger children with PWS than controls; adropin was also higher in older children with PWS. Growth hormone treatment had no effects on obestatin or adropin in PWS. The ratio of ghrelin to obestatin declined from early to late childhood but was higher in older PWS than older controls. Adropin correlated with fasting glucose in the PWS group only. Changes in the ratio of ghrelin to obestatin may suggest changes in the processing of preproghrelin to ghrelin and obestatin during development and differential processing of preproghrelin in PWS.

Autism Spectrum Disorder (ASD) is a developmental disorder characterized by social and communication deficits and repetitive behaviors. Children with ASD are also at a higher risk for developing overweight or obesity than children with typical development (TD). Childhood obesity has been associated with adverse health outcomes, including insulin resistance, diabetes, heart disease, and certain cancers. Importantly some key factors that play a mediating role in these higher rates of obesity include lifestyle factors and biological influences, as well as secondary comorbidities and medications. This review summarizes current knowledge about behavioral and lifestyle factors that could contribute to unhealthy weight gain in children with ASD, as well as the current state of knowledge of emerging risk factors such as the possible influence of sleep problems, the gut microbiome, endocrine influences and maternal metabolic disorders. We also discuss some of the clinical implications of these risk factors and areas for future research.

Magnetic resonance imaging (MRI) provides detailed assessment of body composition compartments. No studies have employed state-of-the-art MRI methods to accurately examine abdominal adipose tissue (AT) and skeletal muscle in youth with Prader-Willi syndrome (PWS). Therefore, this study aimed to describe AT distribution and skeletal muscle in the abdominal region of youth with PWS using MRI.Anthropometric measures and whole-abdominal T1-weighted MRI were performed in sixteen (5 males and 11 females) youth diagnosed with PWS, and seventeen (10 males and 7 females) youth who did not have PWS (controls). Volume of subcutaneous, visceral, intermuscular, and total AT, and skeletal muscle in the abdominal region were quantified using a semiautomatic procedure. Results were summarized using median and interquartile range (IQR, 25th-75th), and ANCOVA test was used (with age and sex as covariates) to examine differences in body composition compartments between PWS and control group.PWS group had similar age (10.5, 6.6-13.9 vs. 12.8, 10.0-14.4years; P=0.14) and BMI z-score (0.5, 0.2-1.3 vs. 0.2, -0.3 to 1.0; P=0.33) when compared with controls. Significant differences were observed in absolute volumes of total AT (PWS: 4.1, 2.0-6.6L; control: 2.9, 2.0-4.5L; P=0.01), subcutaneous AT (PWS: 2.8, 1.4-4.8L; control: 1.8, 1.1-3.2L; P=0.01), and intermuscular AT (PWS: 0.3, 0.1-0.4L; control: 0.3, 0.2-0.3L; P0.005). Visceral AT/subcutaneous AT was lower in PWS (0.4, 0.3-0.5) compared to controls (0.5, 0.4-0.6), P=0.01. In addition, skeletal muscle volume was lower in PWS (1.5, 1.0-2.6L) compared to controls (3.1, 1.6-3.9L), P=0.03. Ratios of abdominal AT compartments to skeletal muscle were all higher in PWS compared to controls (all P0.005).PWS youth have greater abdominal adiposity, particularly subcutaneous AT and intermuscular AT, and lower volume of skeletal muscle compared to controls. The decreased ratio of visceral AT/subcutaneous AT in youth with PWS suggests an improved metabolic profile for the level of adiposity present; however, elevated ratios of AT to skeletal muscle suggest a sarcopenic obesity-like phenotype, which could lead to worse health outcomes.