Prediction of visceral adipose tissue from simple anthropometric measurements in youths with obesity

Prediction of future visceral adiposity and application to cancer research: The Multiethnic Cohort Study

BACKGROUND

We previously developed a prediction score for MRI-quantified abdominal visceral adipose tissue (VAT) based on concurrent measurements of height, body mass index (BMI), and nine blood biomarkers, for optimal performance in five racial/ethnic groups. Here we evaluated the VAT score for prediction of future VAT and examined if enhancement with additional biomarkers, lifestyle behavior information, and medical history improves the prediction.

METHODS

We examined 500 participants from the Multiethnic Cohort (MEC) with detailed data (age 50-66) collected 10 years prior to their MRI assessment of VAT. We generated three forecasted VAT prediction models: first by applying the original VAT equation to the past data on the predictors ("original"), second by refitting the past data on anthropometry and biomarkers ("refit"), and third by building a new prediction model based on the past data enhanced with lifestyle and medical history ("enhanced"). We compared the forecasted prediction scores to future VAT using the coefficient of determination (R2). In independent nested case-control data in MEC, we applied the concurrent and forecasted VAT models to assess association of the scores with subsequent incident breast cancer (950 pairs) and colorectal cancer (831 pairs).

RESULTS

Compared to the VAT prediction by the concurrent VAT score (R2 = 0.70 in men, 0.68 in women), the forecasted original VAT score (R2 = 0.54, 0.48) performed better than past anthropometry alone (R2 = 0.47, 0.40) or two published scores (VAI, METS-VF). The forecasted refit (R2 = 0.61, 0.51) and enhanced (R2 = 0.62, 0.55) VAT scores each showed slight improvements. Similar to the concurrent VAT score, the forecasted VAT scores were associated with breast cancer, but not colorectal cancer. Both the refit score (adjusted OR for tertile 3 vs. 1 = 1.27; 95% CI: 1.00-1.62) and enhanced score (1.27; 0.99-1.62) were associated with breast cancer independently of BMI.

CONCLUSIONS

Predicted VAT from midlife data can be used as a surrogate to assess the effect of VAT on incident diseases associated with obesity, as illustrated for postmenopausal breast cancer.

Anthropometric Equations to Predict Visceral Adipose Tissue in European and American Youth

OBJECTIVE

To investigate whether prediction equations including a limited but selected number of anthropometrics that consider differences in subcutaneous abdominal adipose tissue may improve prediction of the visceral adipose tissue (VAT) in youth.

STUDY DESIGN

Anthropometrics and abdominal adipose tissue by MRI were available in 7-18 years old youth with overweight or obesity: 181 White Europeans and 186 White and Black Americans. Multivariable regressions were performed to develop and validate the VAT anthropometric predictive equations in a cross-sectional study.

RESULTS

A model with both waist circumference (WaistC) and hip circumference (HipC) (VAT = [1.594 × WaistC] - [0.681 × HipC] + [1.74 × Age] - 48.95) more strongly predicted VAT in girls of White European ethnicity (R² = 50.8%; standard error of the estimate [SEE] = 13.47 cm²), White American ethnicity (R² = 41.9%; SEE, 15.63 cm²), and Black American ethnicity (R² = 25.1%; SEE, 16.34 cm²) (P < .001), than WaistC or BMI. In boys, WaistC was the strongest predictor of VAT; HipC did not significantly improve VAT prediction.

CONCLUSIONS

A model including both WaistC and HipC that considers differences in subcutaneous abdominal adipose tissue more accurately predicts VAT in girls and is superior to commonly measured anthropometrics used individually. In boys, other anthropometric measures did not significantly contribute to the prediction of VAT beyond WaistC alone. This demonstrates that selected anthropometric predictive equations for VAT can be an accessible, cost-effective alternative to imaging methods that can be used in both clinics and research.

Validation of the SMH Equations for the Estimation of the Total Body Water Volume in Hemodialysis Patients

Background:

Online dialysis clearance monitors typically provide an accurate value for Kt. A value for V (total body water [TBW]) is required to calculate Kt/V, the measure of the adequacy of the delivered dialysis in hemodialysis (HD) patients. Using bioimpedance spectroscopy (BIS), we previously developed 2 sex-specific equations for the estimation of the TBW, which we have chosen to name the St Michael’s Hospital (SMH) equations.

Objective:

The objective of this study was to validate the SMH equations in a second distinct population of patients.

Design:

Cross-sectional study.

Setting:

Single center hemodialysis unit at St Michael’s Hospital, a tertiary care teaching hospital, in Toronto, Canada.

Patients:

Eighty-one adult HD patients who had been receiving conventional maintenance HD for at least 3 months.

Measurements:

Anthropometric measurements including weight, height, and waist circumference were collected. TBW was measured by BIS using the Body Composition Monitor (Fresenius Medical Care, Bad Homburg, Germany).

Methods:

The Bland-Altman method to calculate the bias and limits of agreement and the difference plot analysis were used to evaluate the difference between the BIS-TBW and the TBW derived from our equations (SMH equation) in this validation cohort.

Results:

The TBW values based on our equations had a high correlation with BIS-TBW (correlation coefficients = 0.93, P values < .01, bias = 1.8 [95% CI: 1-2.6] liter). Application of SMH equations closely predicted Kt/V, based on BIS value, in all categories of waist circumference.

Limitations:

Small sample size, single-center, not including peritoneal dialysis patients. A larger and more heterogeneous sample with more patients at the extremes of body mass index would allow for more detailed sub-group analyses in different races and different anthropometric categories to better understand the performance of these equations in discrete sub-groups of patients.

Conclusions:

In maintenance HD patients, our previously derived equations to estimate the TBW using weight and waist circumference appear to be valid in a distinct patient population. Given the centrality of TBW to the calculation of small molecule clearance, the SMH equations may enhance the measurement of dialysis adequacy and inform practice.

The range of non-traditional anthropometric parameters to define obesity and obesity-related disease in children: a systematic review

Obesity is defined as an abnormal/excessive accumulation of body fat, associated with health consequences. Although overall obesity does confer a significant threat to the health of individuals, the distribution of body fat, especially abdominal/central obesity is of greater importance. For practical reasons, proxy anthropometric measurements have been developed to identify central obesity, however, major limitations are noted in these traditional measurements. The present study aims to evaluate the literature, to identify and describe non-traditional anthropometric measurements of overweight and obesity in children. The current systematic review was conducted in accordance with the PRISMA guidelines, and the search was undertaken in the PubMed^® database, using MeSH (Medical Subject Headings) terms. Data extracted from each study were: (a) details of the study, (b) anthropometric parameter(s) evaluated in the study and its details, (c) study methods, (d) objectives of the study and/or comparisons, and (e) main findings/conclusions of the study. The search yielded a total of 3697 articles, of which 31 studies were deemed eligible to be included. The literature search identified 13 non-traditional anthropometric parameters. Data on non-traditional anthropometric parameters were derived from 24 countries. Majority were descriptive cross-sectional studies (n = 29), while sample size varied from 65 to 23,043. Non-traditional anthropometric parameters showed variable correlation with obesity and/or related metabolic risk factors. Some parameters involved complex calculations, while others were based on a single anthropometric measurement or derived from traditional measures. Most studies lacked comparison with a 'gold standard' assessment of body fat, hence further research is required to determine their accuracy and precision.

Changes in whole metabolites after exenatide treatment in overweight/obese polycystic ovary syndrome patients

OBJECTIVE

Exenatide is a new agent for diabetes therapy, and its use in polycystic ovary syndrome (PCOS) has gradually increased; however, the clinical benefit and metabolic improvement need further evidence. This research aimed to study the changes in whole metabolites before and after exenatide treatment in overweight/obese PCOS patients to gain a better understanding of exenatide for the treatment of PCOS.

METHODS

Sixty-seven women, including 32 with PCOS and 35 age-matched controls, were recruited. The metabolite changes were detected with nontargeted gas chromatography-tandem mass spectrometry (NTGC-MS) before and after exenatide treatment, and changes in clinical biochemical characteristics were also observed.

RESULTS

A total of 62 metabolites were differentially expressed between the healthy and PCOS groups, and 31 differentially expressed metabolites were detected before and after exenatide treatment. Abnormal lipid metabolism and amino acid metabolism were the main metabolic disorders. Exenatide improved lipid and amino acid metabolism, especially amino acid metabolites. Three types of branched-chain amino acids (valine, leucine and isoleucine), two types of aromatic amino acids (phenylalanine and tyrosine) and lysine are important potential metabolites for the therapeutic efficacy of exenatide. Many abnormal metabolic disorders are related to insulin resistance, oxidative stress and even ovulatory dysfunction. Moreover, in this small sample clinical study, we also found that exenatide improved insulin sensitivity, reduced body weight and improved glycolipid metabolism in PCOS.

CONCLUSIONS

NTGC-MS-based metabolic pathway analysis revealed that exenatide has a beneficial effect on overweight/obese PCOS patients by regulating metabolic disorders, especially amino acid disorders.

Alternative waist-to-height ratios associated with risk biomarkers in youth with diabetes: comparative models in the SEARCH for Diabetes in Youth Study

BACKGROUND/OBJECTIVES

The waist-to-height ratio (WHtR) estimates cardiometabolic risk in youth without need for growth charts by sex and age. Questions remain about whether waist circumference measured per protocol of the National Health and Nutrition Examination Survey (WNHAHtR) or World Health Organization (WWHOHtR) can better predict blood pressures and lipid parameters in youth.

PARTICIPANTS/METHODS

WHtR was measured under both anthropometric protocols among participants in the SEARCH Study, who were recently diagnosed with diabetes (ages 5-19 years; N = 2 773). Biomarkers were documented concurrently with baseline anthropometry and again ~7 years later (ages 10-30 years; N = 1 712). For prediction of continuous biomarker outcomes, baseline WNHAHtR or WWHOHtR entered semiparametric regression models employing restricted cubic splines. To predict binary biomarkers (high-risk group defined as the most adverse quartile) linear WNHAHtR or WWHOHtR terms entered logistic models. Model covariates included demographic characteristics, pertinent medication use, and (for prospective predictions) the follow-up time since baseline. We used measures of model fit, including the adjusted-R2 and the area under the receiver operator curves (AUC) to compare WNHAHtR and WWHOHtR.

RESULTS

For the concurrent biomarkers, the proportion of variation in each outcome explained by full regression models ranged from 23 to 46%; for the prospective biomarkers, the proportions varied from 11 to 30%. Nonlinear relationships were recognized with the lipid outcomes, both at baseline and at follow-up. In full logistic models, the AUCs ranged from 0.75 (diastolic pressure) to 0.85 (systolic pressure) at baseline, and from 0.69 (triglycerides) to 0.78 (systolic pressure) at the prospective follow-up. To predict baseline elevations of the triglycerides/HDL cholesterol ratio, the AUC was 0.816 for WWHOHtR compared with 0.810 for WNHAHtR (p = 0.003), but otherwise comparisons between alternative WHtR protocols were not significantly different.

CONCLUSIONS

Among youth with recently diagnosed diabetes, measurements of WHtR by either waist circumference protocol similarly helped estimate current and prospective cardiometabolic risk biomarkers.

Abdominal obesity and prostate cancer risk: epidemiological evidence from the EPICAP study

Obesity is associated with an increased risk of several cancers, but inconsistent results have been observed between body mass index (BMI) and prostate cancer (PCa) risk. However, some associations have been reported with other indicators such as waist circumference (WC) and waist-hip ratio (WHR). We investigated the role of anthropometric indicators in PCa risk based on data from the Epidemiological study of Prostate Cancer (EPICAP).

EPICAP is a population-based case-control study that included 819 incident PCa in 2012–2013 and 879 controls frequency matched by age. Anthropometric indicators (weight, height, WC, and hip circumference) have been measured at interview. Logistic regression models were used to assess odds ratios (ORs) for the associations between anthropometric indicators (BMI, WC and WHR) and PCa risk.

We observed a slight, but not significant increased risk of PCa for men with a WC > 94 cm (OR 1.20, 95% CI 0.92–1.56) and for men with a WHR ≥ 0.95 (OR 1.30, 95% CI 1.00–1.70 between 0.95 and 1.00, OR 1.25, 95% CI 0.96–1.61 above 1.00). Associations were more pronounced after adjustment and stratification for BMI and in men with aggressive PCa.

Our results suggest that abdominal obesity may be associated with an increased risk of PCa, especially aggressive PCa.

Anthropometric dimensions provide reliable estimates of abdominal adiposity: A validation study

Abdominal fat accumulation is a major risk factor for cardiometabolic morbidity and mortality. The purpose of the study is to assess the possibility of developing accurate estimation equations based on body measurements to determine total abdominal (TFA), subcutaneous (SFA) and visceral fat area (VFA). Hungarian volunteers (n=198) aged between 20 and 81 years were enrolled in the study, which was conducted between July and November 2014. All persons underwent anthropometric measurements and computer tomographic (CT) scanning. Sex-specific multiple linear regression analyses were conducted in a subgroup of 98 participants to generate estimation models, then Bland-Altman's analyses were applied in the cross-validation group to compare their predictive efficiency. The variables best predicting VFA were hip circumference, calf circumference and waist-to-hip ratio (WHR) for males (R²=0.713; SEE=5602.1mm²) and sagittal abdominal diameter (SAD), WHR, thigh circumference and triceps skinfold for females (R²=0.845; SEE=3835.6mm²). The SFA prediction equation included SAD, thigh circumference and abdominal skinfold for males (R²=0.848; SEE=4124.1mm²), body mass index and thigh circumference for females (R²=0.861; SEE=5049.7mm²). Prediction accuracy was the highest in the case of TFA: hip circumference and WHR for males (R²=0.910; SEE=5637.2mm²), SAD, thigh circumference and abdominal skinfold for females (R²=0.915; SEE=6197.5mm²) were used in the equations. The results suggested that deviations in the predictions were independent of the amount of adipose tissue. Estimation of abdominal fat depots based on anthropometric traits could provide a cheap, reliable method in epidemiologic research and public health screening to evaluate the risk of cardiometabolic events.

Subtraction of subcutaneous fat to improve the prediction of visceral adiposity: exploring a new anthropometric track in overweight and obese youth

BACKGROUND

The efficiency of traditional anthropometric measurements such as body mass index (BMI) or waist circumference (Waist C) used to replace biomedical imaging for assessing visceral adipose tissue (VAT) is still highly controversial in youth.

HYPOTHESIS AND OBJECTIVES

We evaluated the most accurate model predicting VAT in overweight/obese youth, using various anthropometric measurements and their correlation with different body fat compartments, especially by testing, for the first time in youth, the hypothesis that subtracting the anthropometric measurement the most highly correlated with subcutaneous abdominal adipose tissue (SAAT) and less correlated possible with VAT from an anthropometric abdominal measurement highly correlated with visceral and total abdominal adipose tissue (TAAT), predicts VAT with higher accuracy.

SUBJECTS AND METHODS

VAT and SAAT data resulted from magnetic resonance imaging (MRI) analysis performed on 181 boys and girls (7-17 y) from Diabetes & Endocrinology Care Paediatrics Clinic in Luxembourg. Height, weight, abdominal diameters, waist, hip, and thigh circumferences were measured with a view to developing the anthropometric VAT predictive algorithms.

RESULTS

In girls, subtracting proximal thigh circumference (Proximal Thigh C), the most closely correlated anthropometric measurement with SAAT, from Waist C, the most closely correlated anthropometric measurement with VAT was instrumental in improving VAT prediction, in comparison with the most accurate single VAT anthropometric surrogate. [Formula: see text] Residual analysis showed a negligible estimation error (5 cm² ). In boys, Waist C was the best VAT predictor.

CONCLUSIONS

Subtraction of abdominal subcutaneous fat is important to predict VAT in overweight/obese girls.

Metabolomics biomarker analysis of threatened abortion in polycystic ovary syndrome: a clinical discovery study

In this study, using an advanced metabolomics platform based on UPLC-QTOF-MS, we found that pregnancy significantly altered the profile of metabolites in the plasma of women with PCOS.

Systematic review to identify and appraise outcome measures used to evaluate childhood obesity treatment interventions (CoOR): evidence of purpose, application, validity, reliability and sensitivity

BACKGROUND

Lack of uniformity in outcome measures used in evaluations of childhood obesity treatment interventions can impede the ability to assess effectiveness and limits comparisons across trials.

OBJECTIVE

To identify and appraise outcome measures to produce a framework of recommended measures for use in evaluations of childhood obesity treatment interventions.

DATA SOURCES

Eleven electronic databases were searched between August and December 2011, including MEDLINE; MEDLINE In-Process and Other Non-Indexed Citations; EMBASE; PsycINFO; Health Management Information Consortium (HMIC); Allied and Complementary Medicine Database (AMED); Global Health, Maternity and Infant Care (all Ovid); Cumulative Index to Nursing and Allied Health Literature (CINAHL) (EBSCOhost); Science Citation Index (SCI) [Web of Science (WoS)]; and The Cochrane Library (Wiley) - from the date of inception, with no language restrictions. This was supported by review of relevant grey literature and trial databases.

REVIEW METHODS

Two searches were conducted to identify (1) outcome measures and corresponding citations used in published childhood obesity treatment evaluations and (2) manuscripts describing the development and/or evaluation of the outcome measures used in the childhood intervention obesity evaluations. Search 1 search strategy (review of trials) was modelled on elements of a review by Luttikhuis et al. (Oude Luttikhuis H, Baur L, Jansen H, Shrewsbury VA, O'Malley C, Stolk RP, et al. Interventions for treating obesity in children. Cochrane Database Syst Rev 2009;1:CD001872). Search 2 strategy (methodology papers) was built on Terwee et al.'s search filter (Terwee CB, Jansma EP, Riphagen II, de Vet HCW. Development of a methodological PubMed search filter for finding studies on measurement properties of measurement instruments. Qual Life Res 2009;18:1115-23). Eligible papers were appraised for quality initially by the internal project team. This was followed by an external appraisal by expert collaborators in order to agree which outcome measures should be recommended for the Childhood obesity Outcomes Review (CoOR) outcome measures framework.

RESULTS

Three hundred and seventy-nine manuscripts describing 180 outcome measures met eligibility criteria. Appraisal of these resulted in the recommendation of 36 measures for the CoOR outcome measures framework. Recommended primary outcome measures were body mass index (BMI) and dual-energy X-ray absorptiometry (DXA). Experts did not advocate any self-reported measures where objective measurement was possible (e.g. physical activity). Physiological outcomes hold potential to be primary outcomes, as they are indicators of cardiovascular health, but without evidence of what constitutes a minimally importance difference they have remained as secondary outcomes (although the corresponding lack of evidence for BMI and DXA is acknowledged). No preference-based quality-of-life measures were identified that would enable economic evaluation via calculation of quality-adjusted life-years. Few measures reported evaluating responsiveness.

LIMITATIONS

Proposed recommended measures are fit for use as outcome measures within studies that evaluate childhood obesity treatment evaluations specifically. These may or may not be suitable for other study designs, and some excluded measures may be more suitable in other study designs.

CONCLUSIONS

The CoOR outcome measures framework provides clear guidance of recommended primary and secondary outcome measures. This will enhance comparability between treatment evaluations and ensure that appropriate measures are being used. Where possible, future work should focus on modification and evaluation of existing measures rather than development of tools de nova. In addition, it is recommended that a similar outcome measures framework is produced to support evaluation of adult obesity programmes.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

The population distribution of the sagittal abdominal diameter (SAD) and SAD/height ratio among Finnish adults

Sagittal abdominal diameter (SAD; 'abdominal height' measured in supine position) may improve upon conventional anthropometry for predicting incident cardiometabolic diseases. However, the SAD is used infrequently by practitioners and epidemiologists. A representative survey of Finnish adults in 2000-2001 collected body measurements including SAD (by sliding-beam calliper) using standardized protocols. Sampled non-pregnant adults (ages 30+ years; 79% participation) provided 6123 SAD measurements from 80 health centre districts. Through stratified, complex survey design, these data represented 2.86 million adults at ages 30+ years. SAD ranged from 13.5 to 38.0 cm, with a population mean (standard error) of 21.7 (0.05) cm and median (interquartile range) of 21.0 (19.1-23.4). Median SAD was higher at ages 50+ years compared with ages 30-49 both for men (22.4 [20.5-24.6] vs. 20.8 [19.3-22.7]) and women (21.7 [19.6-23.9] vs. 19.4 [17.8-21.4]). The SAD/height ratio was similar (0.118) for both sexes at 30-39 years, rising more steeply with age for women than men. Attaining only a basic education, compared with a high level, was associated with increased mean (95% confidence interval) SADs for men (22.6 [22.3-22.8] vs. 22.0 [21.7-22.2]) and women (21.8 [21.5-22.0] vs. 20.6 [20.4-20.8]). Finland's early experience with nationally representative SAD measurements provides normative reference values and physiological insights useful for investigations of cardiometabolic risk.

Introducing excess body weight in childhood and adolescence and comparison with body mass index and waist-to-height ratio

BACKGROUND

Weight status in children and adolescents is commonly defined using age- and gender-corrected standard deviation scores for body mass index (BMI-SDS, also called z-scores). Values are not reliable for the extremely obese however. Moreover, paediatricians and parents may have difficulties understanding z-scores, and while percentiles are easier to gauge, the very obese have values above the 99th percentile, making distinction difficult. The notion of excess body weight (EBW) is increasingly applied in adult patients, mainly in the context of bariatric surgery. However, a clear definition is not available to date for the paediatric population.

METHODS

A simple definition of EBW for children and adolescents is introduced, with median weight as a function of height, age and gender (characterized by an asterisk): EBW (%) = 100x(weight-median weight*)/median weight*. EBW is compared with BMI-SDS and waist-to-height ratio (WHtR). Using two data sources (APV registry and German Health Interview and Examination Survey for Children and Adolescents (KiGGS)) including more than 14,000 children, the relationships between these anthropometric and various metabolic parameters are analysed for a group of overweight/obese children who have sought obesity therapy (APV), for the general paediatric population and for the subset of overweight/obese children from the general population (KiGGS).

RESULTS

The three anthropometric parameters are strongly correlated, with the linear correlation coefficients exceeding 0.8 in the general population and 0.75 in those seeking obesity therapy. Moreover, their relationship to metabolic parameters is quite similar regarding correlations and area under the curve from receiver operating characteristic analyses.

CONCLUSIONS

EBW has similar predictive value for metabolic or cardiovascular comorbidities compared with BMI and WHtR. As it is reliable at the extreme end of the obesity spectrum, easily communicable and simple to use in daily practice, it would make a very useful addition to existing tools for working with obese children and adolescents. Its usefulness in assessing weight change needs to be studied however.

Cardiometabolic risk assessments by body mass index z-score or waist-to-height ratio in a multiethnic sample of sixth-graders

Convention defines pediatric adiposity by the body mass index z-score (BMIz) referenced to normative growth charts. Waist-to-height ratio (WHtR) does not depend on sex-and-age references. In the HEALTHY Study enrollment sample, we compared BMIz with WHtR for ability to identify adverse cardiometabolic risk. Among 5,482 sixth-grade students from 42 middle schools, we estimated explanatory variations (R²) and standardized beta coefficients of BMIz or WHtR for cardiometabolic risk factors: insulin resistance (HOMA-IR), lipids, blood pressures, and glucose. For each risk outcome variable, we prepared adjusted regression models for four subpopulations stratified by sex and high versus lower fatness. For HOMA-IR, R² attributed to BMIz or WHtR was 19%–28% among high-fatness and 8%–13% among lower-fatness students. R² for lipid variables was 4%–9% among high-fatness and 2%–7% among lower-fatness students. In the lower-fatness subpopulations, the standardized coefficients for total cholesterol/HDL cholesterol and triglycerides tended to be weaker for BMIz (0.13–0.20) than for WHtR (0.17–0.28). Among high-fatness students, BMIz and WHtR correlated with blood pressures for Hispanics and whites, but not black boys (systolic) or girls (systolic and diastolic). In 11-12 year olds, assessments by WHtR can provide cardiometabolic risk estimates similar to conventional BMIz without requiring reference to a normative growth chart.

Anthropometrics to Identify Overweight Children at Most Risk for the Development of Cardiometabolic Disease

BACKGROUND

Sagittal abdominal diameter (SAD) is a novel anthropometric that correlates more strongly with visceral adipose tissue (VAT) and cardiometabolic disease risk in adults compared with body mass index (BMI). However, little research has evaluated this measurement in children.

OBJECTIVE

To evaluate SAD as a measure of cardiometabolic risk compared with other anthropometrics in overweight/obese children.

METHODS

This study was a cross-sectional subset analysis of 8- to 12-year-old overweight/ obese children. SAD was compared to BMI, waist circumference (WC), BMI z-score, and percent body fat to determine which measurement was most closely associated with cardiometabolic risk factors. A total cardiometabolic risk score comprising all biochemical markers and blood pressure was also compared to these same anthropometrics.

RESULTS

Overweight/obese children (n = 145, mean age 10 ± 1.4 years, mean BMI percentile 97.9 ± 0.02) were included in the analysis. SAD correlated with the greatest number of biochemical markers/blood pressure values including triglycerides (r = .18, P = .03), HgbA1c (r = .21, P = .01), and systolic blood pressure (r = .38, P < .0001). SAD was more strongly correlated to total risk score (r = .25, P = .002) than WC (r = .22, P = .006), BMI (r = .17, P = .04), BMI-z (r = .18, P = .03), and percent body fat (r = .18, P = .03).

CONCLUSION

This is the first study to evaluate SAD in overweight/obese American children as a marker of cardiometabolic disease risk. The results suggest a slightly stronger correlation between SAD and cardiometabolic risk factors in overweight/obese children; however, all correlations were weak. As this was a pilot study, additional research is needed prior to recommending the use of this measurement in clinical practice.

Comparison among T1-weighted magnetic resonance imaging, modified dixon method, and magnetic resonance spectroscopy in measuring bone marrow fat

INTRODUCTION

An increasing number of studies are utilizing different magnetic resonance (MR) methods to quantify bone marrow fat due to its potential role in osteoporosis. Our aim is to compare the measurements of bone marrow fat among T1-weighted magnetic resonance imaging (MRI), modified Dixon method (also called fat fraction MRI (FFMRI)), and magnetic resonance spectroscopy (MRS).

METHODS

Contiguous MRI scans were acquired in 27 Caucasian postmenopausal women with a modified Dixon method (i.e., FFMRI). Bone marrow adipose tissue (BMAT) of T1-weighted MRI and bone marrow fat fraction of the L3 vertebra and femoral necks were quantified using SliceOmatic and Matlab. MRS was also acquired at the L3 vertebra.

RESULTS

Correlation among the three MR methods measured bone marrow fat fraction and BMAT ranges from 0.78 to 0.88 (P < 0.001) in the L3 vertebra. Correlation between BMAT measured by T1-weighted MRI and bone marrow fat fraction measured by modified FFMRI is 0.86 (P < 0.001) in femoral necks.

CONCLUSION

There are good correlations among T1-weighted MRI, FFMRI, and MRS for bone marrow fat quantification. The inhomogeneous distribution of bone marrow fat, the threshold segmentation of the T1-weighted MRI, and the ambiguity of the FFMRI may partially explain the difference among the three methods.

Prediction of Visceral Adipose Tissue Using Air Displacement Plethysmography in Children

OBJECTIVE

To determine the ability of air displacement plethysmography (ADP) to predict visceral adipose tissue (VAT) volume in children.

RESEARCH METHODS AND PROCEDURES

Fifty-five (33 boys/22 girls) white children 13 to 14 years old were studied. Anthropometric measures were collected for body mass, stature, BMI, and waist-to-hip ratio (WHR), and body fat percentage was estimated from triceps and subscapular skinfolds, bioelectrical impedance analysis, and ADP. VAT volume was determined using magnetic resonance imaging, using a multiple slice protocol at levels L1 to L5.

RESULTS

Boys had significantly (p < or = 0.05) less VAT volume than girls [645.1 (360.5) cm(3) vs. 1035.8 (717.3) cm(3)]. ADP explained the greatest proportion of the variance in VAT volume compared with the other anthropometric measures. Multiple regression analysis indicated that VAT volume was best predicted by ADP body fat percentage in boys [r(2) = 0.81, SE of the estimate (SEE) = 160.1, SEE coefficient of variation = 25%] and by WHR and BMI in girls (r(2) = 0.80, SEE = 337.71, SEE coefficient of variation = 33%).

DISCUSSION

Compared with the other anthropometric measures, ADP explains the greatest proportion of the variance in VAT volume in children 13 to 14 years old. For boys, ADP is the tool of choice to predict VAT volume, yet using the more simply collected measures of BMI and WHR is recommended for girls. However, large SE of the estimates remained, suggesting that if precision is needed, there is no surrogate for direct imaging of VAT.

MRI-measured pelvic bone marrow adipose tissue is inversely related to DXA-measured bone mineral in younger and older adults

BACKGROUND/OBJECTIVES

Recent research has shown an inverse relationship between bone marrow adipose tissue (BMAT) and bone mineral density (BMD). There is a lack of evidence at the macro-imaging level to establish whether increased BMAT is a cause or effect of bone loss. This cross-sectional study compared the BMAT and BMD relationship between a younger adult group at or approaching peak bone mass (PBM; age 18.0-39.9 years) and an older group with potential bone loss (PoBL; age 40.0-88.0 years).

SUBJECTS/METHODS

Pelvic BMAT was evaluated in 560 healthy men and women with T1-weighted whole-body magnetic resonance imaging. BMD was measured using whole-body dual-energy X-ray absorptiometry.

RESULTS

An inverse correlation was observed between pelvic BMAT and pelvic, total and spine BMD in the younger PBM group (r=-0.419 to -0.461, P<0.001) and in the older PoBL group (r=-0.405 to -0.500, P<0.001). After adjusting for age, sex, ethnicity, menopausal status, total body fat, skeletal muscle, subcutaneous and visceral adipose tissue, neither subject group (younger PBM vs older PoBL) nor its interaction with pelvic BMAT significantly contributed to the regression models with BMD as dependent variable and pelvic BMAT as independent variable (P=0.434-0.928).

CONCLUSIONS

Our findings indicate that an inverse relationship between pelvic BMAT and BMD is present both in younger subjects who have not yet experienced bone loss and also in older subjects. These results provide support at the macro-imaging level for the hypothesis that low BMD may be a result of preferential differentiation of mesenchymal stem cells from osteoblasts to adipocytes.

Ethnic and sex differences in bone marrow adipose tissue and bone mineral density relationship

The relationship between bone marrow adipose tissue and bone mineral density is different between African Americans and Caucasians as well as between men and women. This suggests that the mechanisms that regulate the differentiation and proliferation of bone marrow stromal cells may differ in these populations.

INTRODUCTION

It has long been established that there are ethnic and sex differences in bone mineral density (BMD) and fracture risk. Recent studies suggest that bone marrow adipose tissue (BMAT) may play a role in the pathogenesis of osteoporosis. It is unknown whether ethnic and sex differences exist in the relationship between BMAT and BMD.

METHODS

Pelvic BMAT was evaluated in 455 healthy African American and Caucasian men and women (age 18-88 years) using whole-body T1-weighted magnetic resonance imaging. BMD was measured using whole-body dual-energy X-ray absorptiometry.

RESULTS

A negative correlation was observed between pelvic BMAT and total body BMD or pelvic BMD (r = -0.533, -0.576, respectively; P < 0.001). In multiple regression analyses with BMD as the dependent variable, ethnicity significantly entered the regression models as either an individual term or an interaction with BMAT. Menopausal status significantly entered the regression model with total body BMD as the dependent variable. African Americans had higher total body BMD than Caucasians for the same amount of BMAT, and the ethnic difference for pelvic BMD was greater in those participants with a higher BMAT. Men and premenopausal women had higher total body BMD levels than postmenopausal women for the same amount of BMAT.

CONCLUSIONS

An inverse relationship exists between BMAT and BMD in African American and Caucasian men and women. The observed ethnic and sex differences between BMAT and BMD in the present study suggest the possibility that the mechanisms regulating the differentiation and proliferation of bone marrow stromal cells may differ in these populations.

Relationship between MRI-measured bone marrow adipose tissue and hip and spine bone mineral density in African-American and Caucasian participants: the CARDIA study

CONTEXT

An increasing number of studies suggest that bone marrow adipose tissue (BMAT) might play a role in the pathogenesis of osteoporosis. Our previous study of Caucasian women demonstrated that there is an inverse relationship between BMAT and whole-body bone mineral density (BMD). It is unknown whether visceral adipose tissue (VAT), sc adipose tissue (SAT), and skeletal muscle had an effect on the relationship between BMAT and BMD.

OBJECTIVE

In the present study we investigated the relationship between pelvic, hip, and lumbar spine BMAT with hip and lumbar spine BMD in the population-based Coronary Artery Risk Development in Young Adults (CARDIA) sample with adjustment for whole-body magnetic resonance imaging (MRI)-measured VAT, SAT, and skeletal muscle.

DESIGN

T1-weighted MRI was acquired for 210 healthy African-American and Caucasian men and women (age 38-52 yr). Hip and lumbar spine BMD were measured by dual-energy x-ray absorptiometry.

RESULTS

Pelvic, hip, and lumbar spine BMAT had negative correlations with hip and lumbar spine BMD (r = -0.399 to -0.550, P < 0.001). The inverse associations between BMAT and BMD remained strong after adjusting for demographics, weight, skeletal muscle, SAT, VAT, total adipose tissue (TAT), menopausal status, lifestyle factors, and inflammatory markers (standardized regression coefficients = -0. 296 to -0.549, P < 0.001). Among body composition measures, skeletal muscle was the strongest correlate of BMD after adjusting for BMAT (standardized regression coefficients = 0.268-0.614, P < 0.05), with little additional contribution from weight, SAT, VAT, or total adipose tissue.

CONCLUSION

In this middle-aged population, a negative relationship existed between MRI-measured BMAT and hip and lumbar spine BMD independent of demographics and body composition. These observations support the growing evidence linking BMAT with low bone density.

Peptides from adipose tissue in monitoring energy balance in infants

BACKGROUND/AIM

Overnutrition as well as undernutrition is a serious problem in hospitalized patients, especially in infants. Routine laboratory tests detecting disturbances in energy balance are not specific or accurate. The aim of this study was to evaluate adiponectin and leptin as markers of short-time energy malnutrition.

METHODS

Forty-five infants fed orally and parenterally were included in the study. Plasma glucose, leptin and adiponectin were measured in a fasting state and postprandially (1 h after the meal), after a minimum of 24 h of total parenteral nutrition (TPN) and after a minimum of 8 h of intravenous infusion of glucose and crystalloids.

RESULTS

Postprandial glucose levels in children fed orally was similar to that observed in children who received intravenous infusion of glucose. The TPN children had slightly higher glucose concentration in contrast to leptin levels which were significantly lower in this group (1.08 mg/mL +/- 0.43) as compared to the others (p < 0.05 in both cases). The mean postprandial levels of the adiponectin in orally fed children were significantly higher (10.7 microg/mL +/- 2.4) than in children with TPN (5.8 microg/mL +/- 2.4; p < 0.001) and in children hydrated intravenously (3.3 microg/mL +/- 2.3; p < 0.001). The concentration of adiponectin correlated significantly with calorie intake.

CONCLUSIONS

Oral meal does not affect the plasma concentrations of leptin and adiponectin in infants. Adiponectin is a good short-time marker of energy malnutrition in infants.

Efficacy of increasing physical activity to reduce children's visceral fat: a pilot randomized controlled trial

OBJECTIVE

To examine whether differentially targeting physical activity within the context of pilot family-based pediatric weight control treatment results in differential change in abdominal fat, particularly visceral fat.

METHOD

Twenty-nine overweight children (>85(th) body mass index [BMI] percentile) and at least one participating parent were randomly assigned to one of two family-based behavioral weight management conditions that either targeted 1) primarily dietary change (STANDARD; n = 15) or 2) dietary plus physical activity change (ADDED; n = 14). Differences at post-treatment in overall child weight status (e.g., BMI), whole-body composition (measured by dual x-ray absorptiometry), and abdominal fat (measured by waist circumference and magnetic resonance imaging) were assessed using intent-to-treat analyses, as were post-treatment parent BMI and waist circumference. Child and parent physical activity and dietary behavior changes were also evaluated. Results. At post-treatment, overall child weight status, whole-body composition, and child dietary measures did not differ by condition. Children in the ADDED condition tended to have higher physical activity and lower visceral abdominal fat at post-treatment relative to children in the STANDARD condition.

CONCLUSIONS

Increasing physical activity may be important to optimize reductions in abdominal fat, especially visceral fat, among overweight children provided with family-based behavioral weight management treatment.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00359957.

Visceral adipose tissue in children and adolescents: a review

Research conducted among adults has mainly shown that visceral adipose tissue (VAT) is strongly linked to insulin resistance, type 2 diabetes, hypertension and dyslipidaemia, leading to increased risk of CVD or the metabolic syndrome. However, little is known about the aetiology, determinants and consequences of VAT in children. The present article reviews the current literature relating to the factors influencing visceral fat accumulation in children and adolescents. The literature used in the present study was collected by searching a PubMed database, in which studies up to 2008 exploring the factors influencing accumulation of visceral fat among children and youth were found on the basis of appropriate keywords. Further studies concerning different factors influencing deposition of VAT among children and youth should first of all concentrate on: carrying out long-term analyses among children of different ethnical groups, which should begin in the period of prepuberty and which should cover the whole period of puberty till adulthood; drawing up norms specifying the amount of VAT among healthy children; identification of anthropometric indicators which will help to determine the VAT:subcutaneous adipose tissue ratio in the most precise way; broader studies of the influence of eating habits on developing VAT deposit among children and youth.

Abdominal fat assessment in adolescents using dual-energy X-ray absorptiometry

BACKGROUND

Abdominal obesity is an increasing problem in adolescents, often persisting into adulthood. Reliable assessment has been restricted to techniques limited by relatively high radiation doses or cost.

AIM

To investigate the reliability of several abdominal regions using dual-energy X-ray absorptiometry (DXA), and to assess the construct validity of these methods against metabolic profile.

METHODS

Inter- and intra-rater precision of two assessors were examined, for fat mass analysis in six different abdominal regions using DXA in overweight/obese and normal weight adolescents. Construct validity was examined in overweight/obese individuals.

RESULTS

All methods had acceptable intra- and inter-rater reliability. Region 1 was most precise in overweight/obese individuals, while Region 6 was most precise in normal weight individuals. In all regions, assessments were less precise in overweight/obese individuals. All regions were equally predictive of insulin outcomes.

CONCLUSIONS

Abdominal adiposity can be reliably assessed in adolescents using DXA, and the most precisely assessed regions were identified. All regions predicted insulin outcomes.

Magnetic resonance imaging of abdominal adiposity in a large cohort of British children

OBJECTIVE

To describe abdominal adipose tissue distribution in a large sample of contemporary British children; to determine the influence of gender, stage of maturation and body mass index (BMI) on abdominal adipose tissue distribution; and to compare the ability of BMI and waist circumference to predict abdominal adipose tissue.

SUBJECTS AND METHODS

A total of 74 boys (mean age 13.4+/-0.4 years) and 96 girls (mean age 13.5+/-0.5 years) were selected from volunteer children enrolled in the Avon Longitudinal Study of Parents and Children (ALSPAC). Height, weight and waist circumference were measured and BMI calculated. Stage of sexual maturation was available for 113 children using a self-report questionnaire based on Tanner's criteria. Magnetic resonance imaging was used to assess subcutaneous abdominal adipose tissue (SAAT) and intra-abdominal adipose tissue (IAAT) volumes and patterning.

RESULTS

Boys had lower levels of IAAT (P=0.036) and SAAT (P=0.003) than girls. IAAT and SAAT were higher in overweight and obese boys and girls when compared with normal weight children (P<0.0001). This pattern was also reflected in waist circumference groups. Boys had higher IAAT/SAAT ratios than girls, indicating proportionately more adipose tissue deposited intra-abdominally (P=0.002). However, both boys and girls deposited less than 10% of their abdominal fat as internal adipose tissue. WC predicted 67.4% of the variance in IAAT (P<0.001), and BMI predicted 84.8% of the variance in SAAT (P<0.001). However, BMI as the best single predictor explained only 8.4% of the variance in the IAAT/SAAT ratio (P<0.001).

CONCLUSIONS

At this age and stage of sexual maturation, the amount of IAAT remains relatively small. WC and BMI offer a feasible alternative to the MRI estimation of IAAT and SAAT, respectively, in a population-based sample of boys and girls. International Journal of Obesity (2008) 32, 91-99; doi:10.1038/sj.ijo.0803780; published online 27 November 2007.

Prediction of visceral fat area at the umbilicus level using fat mass of the trunk: The validity of bioelectrical impedance analysis

The aims of this study were to determine the validity of fat mass of the trunk as a predictor for visceral fat area at the umbilicus level and to develop equations to predict visceral fat mass at the umbilicus level using fat mass of the trunk measured by dual-energy X-ray absorptiometry (DXA) and bioelectrical impedance analysis (BIA). The participants were 121 normal Japanese adults (69 males, 52 females). Another 60 volunteer adults (34 males, 26 females) were recruited for examination of cross-validity. Altogether, 41 adults (15 males, 26 females) in the original group and 19 adults (7 males, 12 females) in the cross-validity group received BIA measurement. We measured fat mass by DXA and the BIA system, which was a single-frequency BIA with 8-point contact electrodes, and visceral fat area by computed tomography. We observed significant correlations for visceral fat area in waist circumference (0.56) and fat mass of the trunk measured by DXA (0.64). There was no significant difference in fat mass of the trunk between the DXA and BIA systems, but the BIA system tended to provide an underestimate compared with DXA. With combined fat mass of the trunk measured by DXA and waist circumference as predictors, visceral fat area was estimated by equation (1) (R = 0.87, R(2) = 0.76, standard error of the estimate = 20.9 cm(2)). When substituting fat mass of the trunk measured by BIA into equation (1), there was no significant difference in visceral fat area between the reference and predicted values. An equation using fat mass of the trunk measured by BIA (equation 2) was obtained (R = 0.89, R(2) = 0.78, standard error of the estimate = 20.7 cm(2)), but a systematic error was found for the males. There was cross-validity in both equations. In conclusion, fat mass of the trunk is an effective predictor for the visceral fat area at the umbilicus level. Fat mass of the trunk measured by BIA might be a valid method to predict visceral fat, although further studies with larger samples taking into account the extent and type of obesity are required.

The thrifty phenotype as an adaptive maternal effect

Human diseases in adulthood are increasingly associated with growth patterns in early life, implicating early-life nutrition as the underlying mechanism. The thrifty phenotype hypothesis proposed that early-life metabolic adaptations promote survival, with the developing organism responding to cues of environmental quality by selecting an appropriate trajectory of growth. Recently, some authors have proposed that the thrifty phenotype is also adaptive in the longer-term, by preparing the organism for its likely adult environment. However, windows of plasticity close early during human development, and subsequent environmental changes may result in the selected trajectory becoming inappropriate, leading to adverse effects on health. This paradox generates uncertainty as to whether the thrifty phenotype is indeed adaptive for the offspring in humans. The thrifty phenotype should not be considered a dichotomous concept, rather it refers to the capacity of all offspring to respond to environmental information during early ontogenetic development. This article argues that the thrifty phenotype is the consequence of three different adaptive processes - niche construction, maternal effects, and developmental plasticity - all of which in humans are influenced by our large brains. While developmental plasticity represents an adaptation by the offspring, both niche construction and parental effects are subject to selection on parental rather than offspring fitness. The three processes also operate at different paces. Human offspring do not become net calories-producers until around 18 years of age, such that the high energy costs of the human brain are paid primarily by the mother, even after weaning. The evolutionary expansion of human brain volume occurred in environments characterised by high volatility, inducing strong selective pressure on maternal capacity to provision multiple offspring simultaneously. The thrifty phenotype is therefore best considered as a manipulation of offspring phenotype for the benefit of maternal fitness. The information that enters offspring phenotype during early development does not predict the likely future environment of the offspring, but rather reflects the mother's own developmental experience and the quality of the environment during her own maturation. Offspring growth trajectory thus becomes aligned with long-term maternal capacity to provision. In contemporary populations, the sensitivity of offspring development to maternal phenotype exposes the offspring to adverse effects, through four distinct pathways. The offspring may be exposed to (1) poor maternal metabolic control (e.g. gestational diabetes), (2) maternally derived toxins (e.g. maternal smoking), or (3) low maternal social status (e.g. small size). Adverse consequences of these effects may then be exacerbated by (4) exposure either to the "toxic" western environment in postnatal life, in which diet and physical activity levels are mismatched with metabolic experience in utero, or at the other extreme to famine. The rapid emergence of the epidemic of the metabolic syndrome in the 20th Century reflects the rapid acceleration in the pace of niche construction relative to the slower physiological combination of developmental plasticity and parental effects.

Elevated total and central adiposity and low physical activity are associated with insulin resistance in children

The aim of this study was 2-fold: (1) to examine insulin resistance, blood lipid levels, and inflammatory markers in 9- to 11.5-year-old obese and lean children and (2) to identify factors that influence insulin resistance in this cohort of youths. Body mass index, skinfold thickness, waist circumference, physical activity (4-day triaxial accelerometer), cardiorespiratory fitness (submaximal bicycle ergometer test), and dietary intake (3-day food records) were evaluated in 27 obese and 27 lean boys and girls. Fasting blood samples were analyzed for insulin, glucose, lipids and lipoproteins, C-reactive protein (CRP), interleukin 6, soluble intercellular adhesion molecule, and soluble vascular cell adhesion molecule. Homeostasis model assessment (HOMA) was used to evaluate insulin resistance (HOMA-IR). Obese children presented higher HOMA-IR, CRP, and blood lipid levels (all P < .01) compared with lean children. Total body fat and waist circumference were positively associated with fasting insulin (r > or = 0.51), HOMA-IR (r > or = 0.56), CRP (r > or = 0.51), and blood triacylglycerol (r > or = 0.38), and were inversely correlated with high-density lipoprotein cholesterol (r > or = -0.39; all P < .01). Cardiorespiratory fitness was inversely associated with HOMA-IR (r = -0.24; P < .05), but this association disappeared when adjusted for age, sex, and fat mass. Waist circumference and total daily physical activity explained 49% of the variance in HOMA-IR in these children. In conclusion, these findings suggest that total and central adiposity are positively associated and physical activity is negatively associated with insulin resistance in children. Interventions to improve glucose metabolism in youth should target at reducing total body and abdominal fat and increasing physical activity. The lack of association between inflammatory markers and HOMA-IR suggests that obesity may precede the elevation of these markers in the evolution of insulin resistance in youth.

Visceral abdominal fat is correlated with whole-body fat and physical activity among 8-y-old children at risk of obesity

BACKGROUND

Abdominal fat is more related to health risk than is whole-body fat. Determining the factors related to children's visceral fat could result in interventions to improve child health.

OBJECTIVE

Given the effects of physical activity on adults' visceral fat, it was hypothesized that, after accounting for whole-body fat, physical activity would be inversely related to children's visceral (VAT), but not to subcutaneous (SAT), abdominal adipose tissue.

DESIGN

In this cross-sectional observational study conducted in forty-two 8-y-old children (21 boys, 21 girls) at risk of obesity [>75th body mass index (BMI) percentile, with at least one overweight parent], familial factors (eg, maternal BMI), historic weight-related factors (eg, birth weight), and the children's current physical activity (self-reported and measured with accelerometry) and diet were examined as potential correlates of the children's whole-body composition (measured with BMI and dual-energy X-ray absorptiometry) and abdominal fat distribution (measured by magnetic resonance imaging).

RESULTS

Accelerometer-measured physical activity was related to whole-body fat (r = -0.32, P < 0.10), SAT (r = -0.29, P < 0.10), and VAT (r = -0.43, P < 0.05). In regression models, whole-body fat was positively associated with and the only significant correlate of SAT. Whole-body fat was positively related and accelerometer-measured physical activity was negatively and independently related to the children's VAT.

CONCLUSIONS

Both SAT and VAT in 8-y-old children at risk of obesity are most closely associated with whole-body fat. However, after control for whole-body fat, greater physical activity is only associated with lower VAT, not SAT, in these children.

Methods for assessing body composition, cardiovascular and metabolic function in children and adolescents: implications for exercise studies

PURPOSE OF REVIEW

To critically evaluate the most recent literature on the methods used to assess body composition, cardiovascular and metabolic function in children and adolescents.

RECENT FINDINGS

Although regional body composition can be fairly accurately calculated by dual-energy X-ray absorptiometry, the accuracy of noninvasive estimations of visceral adipose tissue is questionable. Regarding the cardiovascular and metabolic adaptations, there is no doubt that direct and invasive methods provide high accuracy and reproducibility. For instance, exercise until exhaustion, direct Fick equation, nuclear magnetic resonance and magnetic resonance imaging are valid methods to determine maximum oxygen uptake, cardiac output and tissue substrate metabolism, respectively. Except for the direct Fick equation, all have been successfully used in pediatric studies. Relatively new techniques for the assessment of exercise training-induced adaptations in youths include the thoracic bioimpedance and the Modelflow method for cardiac output determination, and magnetic resonance spectroscopy for intramuscular and intrahepatic lipid content. Additional validation and reliability studies in pediatric populations are needed for some of these techniques (e.g. the Modelflow method).

SUMMARY

Most of the techniques used in adults appear not directly applicable to youths. A combination of techniques and/or the application of new, promising and easy to use ones, such as near-infrared spectroscopy and Laser Doppler flowmetry, may advance our knowledge in pediatric exercise science.

A simplified approach to analysing bio-electrical impedance data in epidemiological surveys

BACKGROUND

Bio-electrical impedance analysis (BIA) is widely used to estimate body composition. It is simple, quick and cheap, but less accurate than other methods. It has potential epidemiological value, but has conventionally required validation before application.

AIMS

To develop a simple method of expressing weight, height and impedance data that avoids the need for population-specific validation equations in order to facilitate epidemiological application.

METHODS

Body composition was measured using the four-component model in young adults (43 males, 90 females). Impedance (R) was measured hand-foot and foot-foot. Lean mass and fat mass were adjusted for height to give lean mass index (LMI) and fat mass index (FMI). Based on theoretical principles, we generated the index 1/R, which provides an index of body water adjusted for height. Sex-specific regression models were used to investigate the relationships between (a) 1/R and LMI, and (b) body mass index (BMI) adjusted for 1/R and FMI. The success of this approach was evaluated in relation to the conventional BIA approach, using correlation analysis.

RESULTS

1/R was a highly significant predictor of LMI. BMI adjusted for 1/R was a significant predictor of FMI. Our approach performed as well as the conventional approach for LMI, but not for FMI.

DISCUSSION

Direct use of BIA data, rather than their combination with population-specific equations for the prediction of total body water, proved successful at ranking individuals of both sexes in terms of LMI and FMI. The index 1/R may prove particularly valuable in epidemiological studies where ranking of LMI is required.

Assessment of obesity status in outpatients from three disease states

AIM

To assess obesity status in patients with cystic fibrosis (CF), human immunodeficiency virus (HIV) and various metabolic disorders (MD), through comparison against a) UK reference data and b) contemporary healthy children.

METHODS

Weight, height, waist circumference (WC), and triceps (TRI) and sub-scapular (SUBS) skinfold thickness were measured in a total of 57 healthy, 49 HIV, 68 MD and 49 CF children. Using published reference data, standard deviation scores (SDS) were calculated.

RESULTS

CF patients had weight, height and BMI SDS significantly below zero. MD patients had height SDS significantly below, and BMI SDS significantly above, zero. Healthy children had BMI SDS significantly above zero. In all three patient groups and healthy children, TRI and WC SDS were significantly above zero. SUBS SDS was also significantly above zero in patients with MD and HIV. WC SDS was greater in patients than in healthy children, but only significantly so for the MD children.

CONCLUSION

In all three patient groups, even those associated with reduced stature or reduced weight, indices of fatness were significantly increased relative to reference data. The tendency to central fatness was evident in healthy children, but was more extreme in patients, especially those with MD.

Measuring body composition

Several aspects of body composition, in particular the amount and distribution of body fat and the amount and composition of lean mass, are now understood to be important health outcomes in infants and children. Their measurement is increasingly considered in clinical practice; however, paediatricians are often unsure as to which techniques are appropriate and suitable for application in specific contexts. This article summarises the pros and cons of measurement technologies currently available for paediatric application. Simple techniques are adequate for many purposes, and simple regional data may often be of greater value than "whole body" values obtained by more sophisticated approaches.

Indices of body composition and chronic morbidity: a cross-sectional study of a rural population in central Russia

Our objective was to clarify how different groups of chronic morbidities are associated with indices of body composition, such as body mass index (BMI), waist circumference (WC), waist to hip ratio (WHR), skinfold index (SF), and fat-free mass index (FFMI). Our sample comprised Chuvasha residing in numerous villages in a rural area of the Russian Federation. The investigated cohort included 787 males aged 18-89 years, and 716 females aged 18-90 years. We performed a cross-sectional, community-based study of a large sample of individuals not receiving any medications for treatment or prevention of chronic morbidities. To elucidate the association between morbidity and age-adjusted anthropometrical indices, we used one-way analysis of variance, wherein the above indices were the dependent variables, while individuals affected vs. nonaffected for a specific disease were the grouping variables. Individuals with ischemic heart disease, diabetes mellitus, hypertension, and peptic ulcer showed significant differences in their BMI, WC, WHR, and SF. In the first diseases, mean values of anthropometric indices were higher in affected individuals, whereas in the peptic ulcer group, mean values were higher in the nonaffected. Skin diseases and gynecological diseases showed significant differences in WHR. Mean values in affected individuals were lower than in the nonaffected. The group afflicted with local forms of arthritis showed significant differences in FFMI, suggesting that arthritis is not linked to obesity, but is linked to high lean mass. Rheumatic diseases positively correlated with WC and FFMI.

Aerobic exercise training improves insulin sensitivity without changes in body weight, body fat, adiponectin, and inflammatory markers in overweight and obese girls

The aim of this study was to examine the effect of aerobic exercise training on insulin sensitivity in overweight and obese girls. Nineteen overweight and obese girls (mean +/- SD: age, 13.1+/-1.8 years; body mass index, 26.8+/-3.9 kg/m(2)) volunteered for this study. Body composition (dual-energy x-ray absorptiometry), insulin sensitivity (oral glucose tolerance test and homeostasis model assessment estimate of insulin resistance; n=15), adiponectin, C-reactive protein (CRP), interleukin (IL) 6, insulin-like growth factor-1, soluble intercellular adhesion molecule-1 and soluble vascular cell adhesion molecule-1 serum levels, and blood lipids and lipoproteins were assessed before and after 12 weeks of aerobic training. Cardiorespiratory fitness increased by 18.8% (P<.05) as a result of training. The area under the insulin concentration curve (insulin area under the curve) decreased by 23.3% (12781.7+/-7454.2 vs 9799.0+/-4918.6 microU.min/mL before and after intervention, respectively; P=.03). Insulin sensitivity was improved without changes in body weight (pre-intervention, 67.9+/-14.5 kg; post-intervention, 68.3+/-14.0 kg) or percent body fat (pre-intervention, 41.4% +/- 4.8%; post-intervention, 40.7%+/-5.2%). The lower limb fat-free mass increased by 6.2% (P<.01) as a result of training, and changes in lower limb fat-free mass were correlated with changes in the insulin area under the curve (r= -.68; P< .01). Serum adiponectin, IL-6, and CRP concentrations did not change (pre-intervention vs post-intervention: adiponectin, 9.57+/-3.01 vs 9.08+/-2.32 microg/mL; IL-6, 1.67+/-1.29 vs 1.65+/-1.25 pg/mL, CRP, 3.21+/-2.48 vs 2.73+/-1.88 mg/L) whereas insulin-like growth factor-1 was lower after training (pre-intervention, 453.8 +/- 159.3 ng/mL; post-intervention, 403.2+/- 155.1 ng/mL; P<.05). In conclusion, 12 weeks of aerobic training improved insulin sensitivity in overweight and obese girls without change in body weight, percent body fat, and circulating concentrations of adiponectin, IL-6, CRP, and other inflammatory markers. These findings suggest that increased physical activity may ameliorate the metabolic abnormalities associated with obesity in children with a mechanism other than the parameters cited earlier.

Are age references for waist circumference, hip circumference and waist-hip ratio in Dutch children useful in clinical practice?

The aim of this study was to present age references for waist circumference (WC), hip circumference (HC), and waist/hip ratio (WHR) in Dutch children. Cross-sectional data were obtained from 14,500 children of Dutch origin in the age range 0-21 years. National references were constructed with the LMS method. This method summarises the distribution by three smooth curves representing skewness (L curve), the median (M curve), and coefficient of variation (S curve). The correlations between body mass index-standard deviation score (BMI-SDS), the circumferences and their ratio, and demographic variables were assessed by (multiple) regression analysis for three age groups: 0-<5 years (1), 5-<12.5 years (2), and 12.5-<21 years (3). A cut-off for clinical use was suggested based on the International Obesity Task Force criteria for BMI. Mean WC and HC values increased with age. Mean WC was slightly higher in boys than in girls, and this difference was statistically significant from 11 years of age onwards. In contrast, HC was significantly higher in girls than in boys from 9 years onwards. The correlation between WC-SDS and BMI-SDS ( r =0.73, P <0.01) and between HC and BMI-SDS ( r =0.67, P <0.01) increased with age. With regard to WHR-SDS, a low correlation was found for 12.5-20 years of age ( r =0.2, P <0.01). WC-SDS correlated positively with height SDS ( r =0.35, P <0.01).

CONCLUSION

Waist circumferences can be used to screen for increased abdominal fat mass in children, whereby a cut-off point of 1.3 standard deviation score seems most suitable.

Comparison of anthropometric parameters as predictors of serum lipids in premenopausal women

No single anthropometric parameter has yet been generally accepted as being superior to others in assessing the metabolic risk associated with abdominal obesity. To compare waist circumference (WC) with waist-to-hip ratio (WHR) and waist-to-height ratio (WHtR), regarding their association with serum lipids, we studied 166 women aged 20 to 48 yr; 53 were obese [body mass index (BMI) 30-39.9 Kg/m2], 50 were overweight (BMI 25-29.9 Kg/m2) and 63 normal weight (BMI 18.5-24.9 Kg/m2). Height, body weight, waist and hip circumferences, total serum cholesterol (Ch), low (LDL) and high density lipoprotein (HDL)-Ch and triglyceride (TG) concentrations were measured. The correlation coefficients between the concentration of serum lipid fractions and each anthropometric parameter did not differ significantly for any lipid variable when WC, WHR and WHtR were compared in the 166 women. The same applied for the obese and the overweight group, whereas in normal weight women there was significant association only between WC and LDL-Ch and between WHR and Ch/HDL-Ch ratio. Stepwise regression analysis showed that the proportion of variance in serum lipids did not change significantly when WHR or WHR+WHtR were added to WC into the regression model (18%, 18% and 18% for Ch; 13%, 18% and 18% for HDL-Ch; 18%, 18% and 12% for LDL-Ch; 35%, 35% and 37% for TG, respectively). These results indicate that WC is the main parameter associated with serum lipid levels and that the ratios studied do not provide additional substantial information in women who need weight management.

Childhood obesity in Canada: a review of prevalence estimates and risk factors for cardiovascular diseases and type 2 diabetes

Childhood obesity in Canada has become increasingly prevalent over the past 2 decades. Despite inconsistencies regarding different anthropometric indicators, cut-offs, and reference populations, both regional and national investigations have revealed high numbers of overweight and obese children and adolescents. A number of risk factors and health consequences have been associated with increased levels of body fatness in youth. Specifically, risk factors for cardiovascular diseases (CVD) and type 2 diabetes are known to develop early in life and tend to emerge in clusters among overweight youngsters. Unhealthy lifestyle behaviours (i.e., physical inactivity), a genetic disposition, and a centralized body fat distribution, all contribute to increased risk. In order to prevent future generations of children from experiencing increased morbidity and mortality as overweight and obese adults, coordinated efforts at all levels (family, school, community, and government) must be established with a long-term commitment to promote healthy nutrition and physical activity behaviours in our youth.

Effects of exercise intensity on cardiovascular fitness, total body composition, and visceral adiposity of obese adolescents

BACKGROUND

Little is known about how the intensity of exercise influences cardiovascular fitness and body composition, especially in obese adolescents.

OBJECTIVE

Our goal was to determine the effects of physical training intensity on the cardiovascular fitness, percentage of body fat (%BF), and visceral adipose tissue (VAT) of obese adolescents.

DESIGN

Obese 13-16-y-olds (n = 80) were assigned to 1) biweekly lifestyle education (LSE), 2) LSE + moderate-intensity physical training, or 3) LSE + high-intensity physical training. The intervention lasted 8 mo. Physical training was offered 5 d/wk, and the target energy expenditure for all subjects in physical training groups was 1047 kJ (250 kcal)/session. Cardiovascular fitness was measured with a multistage treadmill test, %BF with dual-energy X-ray absorptiometry, and VAT with magnetic resonance imaging.

RESULTS

The increase in cardiovascular fitness in the high-intensity physical training group, but not in the moderate-intensity group, was significantly greater than that in the LSE alone group (P = 0.009); no other comparisons of the 3 groups were significant. Compared with the LSE alone group, a group composed of subjects in both physical training groups combined who attended training sessions >or=2 d/wk showed favorable changes in cardiovascular fitness (P < 0.001), %BF (P = 0.001), and VAT (P = 0.029). We found no evidence that the high-intensity physical training was more effective than the moderate-intensity physical training in enhancing body composition.

CONCLUSIONS

The cardiovascular fitness of obese adolescents was significantly improved by physical training, especially high-intensity physical training. The physical training also reduced both visceral and total-body adiposity, but there was no clear effect of the intensity of physical training.

Threshold values of visceral fat measures and their anthropometric alternatives for metabolic derangement in Japanese obese boys

OBJECTIVE

To determine whether the direct measure of visceral adipose tissue (VAT) by computed tomography (CT) is a superior diagnostic criterion to the anthropometric surrogates and more classical criteria of obesity.

DESIGN

Cross-sectional, clinical study. Obese boys were classified according to the occurrence of abnormal values in either serum triglyceride, alanine aminotransferase or insulin level. A threshold value of each criterion for such metabolic derangement was calculated, using the analysis of receiver operating characteristic (ROC) curve.

SUBJECTS

Seventy-five consecutive outpatient Japanese obese boys, ranging in age from 6 to 14 y, were studied.

MEASUREMENTS

Anthropometric indices measured were height, body weight, waist girth, hip girth, triceps and subscapular skinfold thicknesses. Classical criteria for obesity used were percentage overweight (POW), body mass index (BMI) and percentage body fat. Waist girth, sagittal diameter by CT and waist-hip ratio (WHR) were evaluated as anthropometric surrogates for VAT. The areas of total abdominal fat (TAF), VAT and subcutaneous adipose tissue (SAT) were measured by CT at the level of the umbilicus. Clinical blood biochemistry was analyzed in fasting blood samples of obese boys.

RESULTS

Thirty-three boys were classified into a no-complication group, and 42 into a complication group. TAF, VAT and SAT areas were closely associated with age, body size and degree of overweight and adiposity, while VAT/SAT was not. VAT area, sagittal diameter, TAF area and waist girth were closely correlated with alanine aminotransferase, insulin, TG and HDL-C. VAT/SAT, BMI, SAT area, WHR, percentage body fat and POW were less closely associated with these biochemical indices. The descending order of the values of area under the curve for the ROC curves were as follows: VAT>sagittal diameter>TAF>VAT/SAT>waist girth>BMI>WHR>percentage body fat>POW. Both VAT area and VAT/SAT gave >80% of sensitivity and specificity. Among the anthropometric indices studied, the sagittal diameter was the best surrogate of visceral fat measure. The sensitivity and specificity for the rest of the anthropometric indices were in an unsatisfactory range. The threshold values for VAT area, VAT/SAT and sagittal diameter were 58.0 cm(2), 0.276 and 19.2 cm, respectively.

CONCLUSION

The threshold values for VAT area, VAT/SAT and sagittal diameter for detecting biochemical complication in Japanese obese boys were lower than the respective values reported in adults. These values can be used for classifying the obese boys into two types: those with medical problem and those without.

Larger amounts of visceral adipose tissue in Asian Americans

OBJECTIVE

Excess visceral adipose tissue (VAT) is recognized as an important risk factor for the development of coronary heart disease and type 2 diabetes. Several studies have reported less VAT in African Americans compared with whites. As little is known about the levels of VAT in Asians, we compared whole-body VAT in Asian Americans with European Americans.

RESEARCH METHODS AND PROCEDURES

VAT was measured using whole-body multislice magnetic resonance imaging in 54 women (18 Asian Americans, 36 European Americans) and 53 men (19 Asian Americans, 34 European Americans) with body mass index (measured in kilograms per square meter) < 30. Data were analyzed by multiple regression modeling.

RESULTS

Asian American women had higher log-transformed VAT compared with European American women (p < 0.05), after adjusting for age and total body fat. There was a significant age by race interaction such that race differences in VAT were most evident over the age of 30 years. No differences in VAT could be detected between Asian American and European American men, even after adjusting for potential covariates, including total adiposity.

DISCUSSION

These data are the first to demonstrate higher amounts of VAT in healthy Asian Americans, a finding that suggests normative VAT values or standards derived from whites may not be applicable to Asians.

Critical value for the index of body fat distribution based on waist and hip circumferences and stature in obese girls

OBJECTIVE

To determine the critical value for the standard deviation score (SDS) of waist-hip ratio (WHR)/height (Ht), as an age-adjusted measure of body fat distribution, in relation to occurrence of biochemical complications in obese girls.

DESIGN

Cross-sectional, clinical study. The (WHR/Ht)-SDS was calculated as described previously. Obese girls were classified into two groups according to the occurrence of abnormal values in either serum triglyceride, alanine aminotransferase or insulin level. The criteria for obesity were subjected to the receiver operating characteristic (ROC) analysis.

SUBJECTS

One-hundred and twenty-four outpatient Japanese obese girls, ranging in age from 9 to 15 y.

MEASUREMENTS

Height, body weight, waist girth and hip girth as anthropometric measures. Percentage overweight, waist girth, WHR and (WHR/Ht)-SDS as criteria for obesity. Clinical laboratory analysis for fasting blood samples of obese children.

RESULTS

Fifty-nine girls were classified into the no complication group, and 65 girls into the complication group. Those with complications were older, more obese, and their waist girth and WHR were larger, than the girls without complications. The (WHR/Ht)-SDS was >2-fold higher and lipoprotein profile was more atherogenic in the complication group than in the no complication group. Among the four criteria of obesity, (WHR/Ht)-SDS gave the ROC curve skewed furthest into the top left corner of the diagram. Both sensitivity and specificity for (WHR/Ht)-SDS were >80% at the critical value of 2.00. The sensitivity for waist girth was as high as that for specificity for the rest of the criteria were <80%.

CONCLUSION

Only (WHR/Ht)-SDS showed high enough sensitivity and specificity to predict metabolic derangement in the present obese girls. (WHR/Ht)-SDS can serve as the diagnostic criterion that classifies obesity in Japanese adolescent girls into two types.