Race and gender differences in the relationships between anthropometrics and abdominal fat in youth

Sex Differences in Biochemical Analyses, Cardiometabolic Risk Factors and Their Correlation with CRP in Healthy Mexican Individuals

BACKGROUND

Few studies have been undertaken to detect the presence of cardiovascular risk factors (CRFs) in healthy populations (individuals auto-reported as healthy). These risk factors include high body mass index (BMI), high waist-to-hip ratio (WHR), high systolic and diastolic blood pressure (SBP, DBP), high uric acid and high Castelli's risk index (CRI); this last is the ratio of total cholesterol to HDL cholesterol (TC/HDL-c). In addition, the correlations between CRFs and the biomarker C-reactive protein (CRP) has not been explored in each sex.

AIM

Therefore, this study aimed to determine sex differences in the abnormalities in blood and urine analyses, including CRFs and their correlation with CPR in a non-representative sample of healthy Mexican individuals.

RESULTS

A total of 238 subjects were included, 123 (51.7%) of whom were women. The main blood alterations detected were high serum lipids, including high total cholesterol, LDL-cholesterol, triglycerides, and the CRI, which were higher in men than in women. The men's samples had a higher frequency of hypertensives and pre-hypertensives than the women's sample. The CRP showed positive significant correlations with the CRFs: BMI, WHR, SBP, DBP, uric acid, and the CRI, with a higher correlation for BMI and WHR, and most of these correlations were higher in women than in men. Additionally, all these factors showed a positive correlation among them.

CONCLUSION

In conclusion, the main alterations observed in blood are related to cardiovascular risk and were reported with a higher frequency in men when compared with women. This finding can be related to the higher values of WHR in this sex; additionally, the inflammatory marker CRP was more correlated with the cardiometabolic risk factors in women than in men, which suggests a different relationship between inflammation and cardiometabolic risk factors in each sex.

Pediatric body composition based on automatic segmentation of computed tomography scans: a pilot study

BACKGROUND

Body composition during childhood may predispose to negative health outcomes later in life. Automatic segmentation may assist in quantifying pediatric body composition in children.

OBJECTIVE

To evaluate automatic segmentation for body composition on pediatric computed tomography (CT) scans and to provide normative data on muscle and fat areas throughout childhood using automatic segmentation.

MATERIALS AND METHODS

In this pilot study, 537 children (ages 1-17 years) who underwent abdominal CT after high-energy trauma at a Dutch tertiary center (2002-2019) were retrospectively identified. Of these, the CT images of 493 children (66% boys) were used to establish normative data. Muscle (psoas, paraspinal and abdominal wall) and fat (subcutaneous and visceral) areas were measured at the third lumbar vertebral (L3) level by automatic segmentation. A representative subset of 52 scans was also manually segmented to evaluate the performance of automatic segmentation.

RESULTS

For manually-segmented versus automatically-segmented areas (52 scans), mean Dice coefficients were high for muscle (0.87-0.90) and subcutaneous fat (0.88), but lower for visceral fat (0.60). In the control group, muscle area was comparable for both sexes until the age of 13 years, whereafter, boys developed relatively more muscle. From a young age, boys were more prone to visceral fat storage than girls. Overall, boys had significantly higher visceral-to-subcutaneous fat ratios (median 1.1 vs. 0.6, P<0.01) and girls higher fat-to-muscle ratios (median 1.0 vs. 0.7, P<0.01).

CONCLUSION

Automatic segmentation of L3-level muscle and fat areas allows for accurate quantification of pediatric body composition. Using automatic segmentation, the development in muscle and fat distribution during childhood (in otherwise healthy) Dutch children was demonstrated.

Sex Differences in the Atherogenic Risk Index in Healthy Mexican Population and Its Relationship with Anthropometric and Psychological Factors

Dyslipidemia is a risk factor for cardiovascular disease and mortality; however, the association of this variable with a wide range of personal and psychological variables has not been researched. Therefore, the aim of this study was to compare lipid levels and anthropometric measures between sexes and to determine the association between personal and psychological variables with the atherogenic risk index (ARI). An adult population which auto-reported as healthy was invited to participate via social media and in person. They filled out a questionnaire with personal and psychological variables; in addition, the body mass index (BMI) and waist-to-hip ratio (WHR) were measured, and a blood sample was obtained to determine serum lipids. A total of 172 participants were included, from which 92 (53.49%) were women; both sexes were comparable in age and most sociodemographic values. Men showed significantly higher levels of total cholesterol, LDL cholesterol, triglycerides, ARI, and lower levels of HDL cholesterol. The men also showed higher values of WHR than the women. In the bivariate analysis, ARI showed the highest correlation with WHR (r = 0.664) in the men and with BMI (r = 0.619) in the women. In the multivariate analysis, the quality of food intake was negatively correlated with ARI in the global and women's samples, and the psychological variables of assertiveness and positive relations with others were negatively correlated with ARI in women, while purpose in life was negatively correlated with ARI in men. In conclusion, the higher levels of serum lipids and ARI in men can be explained by the higher values of WHR in this sex. Behavioral and psychological variables could be protective factors for high ARI.

A Review of Anthropometric Measurements for Saudi Adults and Elderly, Directions for Future Work and Recommendations to Establish Saudi Guidelines in Line with the Saudi 2030 Vision

Body weight is a significant risk factor for the disease burden of noncommunicable diseases (NCDs). Anthropometric measurements are the first step in determining NCDs risk, and clinicians must have access to valid cutoffs. This study aims to review the literature of Saudi national guidelines and studies previously conducted in Saudi Arabia (SA) and to provide insights and recommendations to establish national guidelines in anthropometric measurements for Saudi adults/elderly in line with the Saudi 2030 Vision. In total, 163 studies were included, and 12 of them contributed to the development of specific anthropometric cutoffs. Cutoffs for metabolic syndrome, waist circumference, and body mass index were established in Saudi adults. However, limited studies were conducted in the elderly. This review warrants establishing standard cutoffs of Saudi adult anthropometrics to avoid over/underreporting of malnutrition and adiposity. This review will help policymakers and the Ministry of Health to establish national guidelines and standard cutoffs to be used in SA for anthropometric measurements that may assist in detecting malnutrition and NCDs.

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.

Influence of Waist Circumference Measurement Site on Visceral Fat and Metabolic Risk in Youth

Although the rate of childhood obesity seems to have plateaued in recent years, the prevalence of obesity among children and adolescents remains high. Childhood obesity is a major public health concern as overweight and obese youth suffer from many co-morbid conditions once considered exclusive to adults. It is now well demonstrated that abdominal obesity as measured by waist circumference (WC) is an independent risk factor for cardiovascular disease and metabolic dysfunction in youth. Despite the strong associations between WC and cardiometabolic risk factors, there is no consensus regarding the optimal WC measurement sites to assess abdominal obesity and obesity-related health risk in children and adolescents. Currently, the WC measurement site that provides the best reflections of visceral fat and the best correlations with cardiometabolic risk factors is unclear. The purpose of this review is to explore whether WC measurement sites influence the relationships between WC, visceral fat, and cardiometabolic risk factors in children and adolescents.

Association between serum vitamin D levels and visceral adipose tissue among adolescents: a cross-sectional observational study in NHANES 2011–2015

Background

In recent years, obesity and vitamin D deficiency are more prevalent among adolescents. Improving our knowledge of the link between vitamin D and visceral adipose tissue (VAT) is essential for the health of adolescents. This study aimed to examine the connection between serum vitamin D levels and VAT mass among adolescents participating in the United States.

Methods

This is a cross-sectional study that used data from the 2011 to 2015 National Health and Nutrition Examination Survey (NHANES). The connection between serum vitamin D levels and VAT was investigated using weighted multiple linear regression models. Potential nonlinear relationships were explored using smooth curve fitting.

Results

The analysis included 3171 adolescents aged 12–19 years. Vitamin D levels were shown to be inversely linked with VAT in the full-adjusted model (β = − 0.34, 95% CI: − 0.49 to − 0.19). When stratified analyses by gender, this negative relationship persisted in the girls’ group (β = − 0.39, 95% CI: − 0.60 to − 0.19), but not in the boys’ group (β = − 0.06, 95% CI: − 0.25 to 0.13). When stratified analysis by race, this negative relationship persisted in the Mexican American group (β = − 0.61, 95% CI: − 1.03 to − 0.19), and the non-Hispanic White group (β = − 0.27, 95% CI: − 0.54 to − 0.01), but not in the other groups.

Conclusions

Our findings confirmed that serum vitamin D levels negatively correlated with VAT among adolescents in the United State, especially in girls, the Mexican American and non-Hispanic White. Further research is needed to determine whether increasing serum vitamin D levels decrease VAT among adolescents.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-022-03688-2.

The Differential Effects of Adiposity and Fitness on Functional Connectivity in Preadolescent Children

PURPOSE

Childhood obesity is a global health concern, with >340 million youth considered overweight or obese. In addition to contributing greatly to health care costs, excess adiposity associated with obesity is considered a major risk factor for premature mortality from cardiovascular and metabolic diseases and is also negatively associated with cognitive and brain health. A complementary line of research highlights the importance of cardiorespiratory fitness, a by-product of engaging in physical activity, on an abundance of health factors, including cognitive and brain health.

METHODS

This study investigated the relationship among excess adiposity (visceral adipose tissue [VAT], subcutaneous abdominal adipose tissue), total abdominal adipose tissue, whole-body percent fat [WB%FAT], body mass index (BMI), and fat-free cardiorespiratory fitness (FF-V̇O 2max ) on resting-state functional connectivity (RSFC) in 121 ( f = 68) children (7-11 yr) using a data-driven whole-brain multivoxel pattern analysis.

RESULTS

Multivoxel pattern analysis revealed brain regions that were significantly associated with VAT, BMI, WB%FAT, and FF-V̇O 2 measures. Yeo's (2011) RSFC-based seven-network cerebral cortical parcellation was used for labeling the results . Post hoc seed-to-voxel analyses found robust negative correlations of VAT and BMI with areas involved in the visual, somatosensory, dorsal attention, ventral attention, limbic, frontoparietal, and default mode networks. Further, positive correlations of FF-V̇O 2 were observed with areas involved in the ventral attention and frontoparietal networks. These novel findings indicate that negative health factors in childhood may be selectively and negatively associated with the 7 Yeo-defined functional networks, yet positive health factors (FF-V̇O 2 ) may be positively associated with these networks.

CONCLUSIONS

These novel results extend the current literature to suggest that BMI and adiposity are negatively associated with, and cardiorespiratory fitness (corrected for fat-free mass) is positively associated with, RSFC networks in children.

A Comprehensive Overview of the Physical Health of the Adolescent Brain Cognitive Development Study Cohort at Baseline

Physical health in childhood is crucial for neurobiological as well as overall development, and can shape long-term outcomes into adulthood. The landmark, longitudinal Adolescent Brain Cognitive Development StudySM (ABCD study®), was designed to investigate brain development and health in almost 12,000 youth who were recruited when they were 9-10 years old and will be followed through adolescence and early adulthood. The overall goal of this paper is to provide descriptive analyses of physical health measures in the ABCD study at baseline, including but not limited to sleep, physical activity and sports involvement, and body mass index. Further this summary will describe how physical health measures collected from the ABCD cohort compare with current normative data and clinical guidelines. We propose this data set has the potential to facilitate clinical recommendations and inform national standards of physical health in this age group. This manuscript will also provide important information for ABCD users and help guide analyses investigating physical health including new avenues for health disparity research as it pertains to adolescent and young adult development.

Assessing visceral and subcutaneous adiposity using segmented T2-MRI and multi-frequency segmental bioelectrical impedance: A sex-based comparative study

BACKGROUND AND AIM

This study aims to quantify abdominal visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) using T2-weighted magnetic resonance imaging (MRI), and assess the extent of its concordance with VAT surface-area measured by a state-of-the-art segmental multi-frequency bioelectrical impedance analysis (BIA) device. A comparison between manual and semi-automated segmentation was conducted. Further, abdominal VAT and SAT sex-based comparison in healthy Arab adults was piloted.

METHODS

A cross-sectional design was followed to recruit subjects. Abdominal VAT and SAT were determined on T2-weighted MRI manually and semi-automatically. Body composition was assessed using a BIA machine. Statistical differences between the abdominal VAT areas defined by BIA, manual, and semi-automated MRI were compared. Correlation between all methods was assessed, and statistical differences between sex abdominal VAT/SAT defined areas were compared.

RESULTS

A total of 165 abdominal T2-weighted MR images taken for 55 overweight/obese adult subjects were analyzed Differences between manual and semi-automated MRI-obtained abdominal VAT and SAT were found statistically significant (P<0.001) for all subjects. Mean abdominal VAT using the BIA technique was found to correlate significantly with manually and semi-automated T2-weighted MRI defined VAT (r=0.7436; P<0.001 and r=0.8275; P<0.001, respectively). Abdominal VAT was significantly (P<0.001) different between male and female subjects accumulating at different abdominal levels.

CONCLUSION

Semi-automatic segmentation showed a stronger significant correlation with BIA compared to manual segmentation, implying a more reliable quantification of abdominal VAT/SAT. Segmental BIA technique may serve as a feasible and convenient assessment tool for the visceral adiposity in obese subjects.

Sex and Ethnic Differences in the Relationship between Changes in Anthropometric Measurements and Visceral Fat in Adolescents with Obesity

OBJECTIVE

To examine sex and ethnic differences in how baseline and changes in anthropometric measures relate with change in visceral fat with interventions in adolescents.

STUDY DESIGN

Black and white adolescents (n = 143: body mass index [BMI] ≥85th percentile, 12-18 years) who participated in intervention studies (3-6 months) were included and had assessments of anthropometric measures (weight, BMI, waist circumference, waist-to-hip ratio [WHR], and waist-to-thigh ratio) and visceral fat at L4-L5 by magnetic resonance imaging before and after interventions.

RESULTS

At baseline, all of the anthropometric measures were positively associated with visceral fat (P < .05), with weight, waist circumference, and WHR having the largest variance explained (model adjusted R² = 0.35-0.47 vs 0.32-0.35). Blacks had 11.5-23.3 cm² less visceral fat compared with whites for a given anthropometric value. Girls tended to have less visceral fat for a given anthropometric value, but the sex differences were not consistently significant (range: 0.7-12.9 cm²). Changes in waist circumference, BMI, and weight, but not WHR, remained significantly associated with changes in visceral fat. There were no sex differences, and much more minimal ethnic differences (<4.9 cm²).

CONCLUSIONS

At baseline, there are sex and ethnic differences in how anthropometric measures correlate with visceral fat. However, there were minimal sex and ethnic differences in how changes in anthropometric measures related with changes in visceral fat. Although all of the anthropometric measures were associated with visceral fat at baseline, waist circumference, BMI, and weight, but not WHR were associated with changes in visceral fat.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT00739180, NCT01323088, and NCT01938950.

Association Between Early Life Weight Gain and Abdominal Fat Partitioning at 4.5 Years is Sex, Ethnicity, and Age Dependent

OBJECTIVE

The aim of this study was to investigate the independent associations between age-specific annual weight gain from birth to age 4 years and fat deposition in metabolically distinct compartments at age 4.5 years in a South Asian longitudinal birth cohort.

METHODS

Volumetric abdominal magnetic resonance imaging with comprehensive segmentation of deep and superficial subcutaneous adipose tissue (SAT) and visceral adipose tissues (VAT) was performed in 316 children (150 boys and 166 girls in three ethnic groups; 158 Chinese, 94 Malay, and 64 Indian) aged 4.5 years. Associations between fat volumes and annual relative weight gain conditional on past growth were assessed overall and stratified by sex and ethnicity.

RESULTS

Conditional relative weight gain had stronger associations with greater SAT and VAT at age 4.5 years in girls than boys and in Indians compared with Malay and Chinese. Overall, the magnitude of association was the largest during 2 to 3 years for SAT and 1 to 2 years for VAT. Despite similar body weight, Indian children and girls had the highest deep and superficial SAT volumes at age 4.5 years (all interactions P < 0.05). No significant sex or ethnic differences were observed in VAT. With increasing BMI, Indian children had the highest tendency to accumulate VAT, and girls accumulated more fat than boys in all depots (all interactions P < 0.001).

CONCLUSIONS

Indian ethnicity and female sex predisposed children to accumulate more fat in the VAT depot with increasing conditional relative weight gain in the second year of life. Thus, 1 to 2 years of age may be a critical window for interventions to reduce visceral fat accumulation.

Adipose Tissue Insulin Resistance in Youth on the Spectrum From Normal Weight to Obese and From Normal Glucose Tolerance to Impaired Glucose Tolerance to Type 2 Diabetes

OBJECTIVE

Adipose tissue insulin resistance is one of the pathophysiological components of type 2 diabetes. Herein we investigated: 1) adipose insulin resistance index (Adipose-IR) (calculated as fasting insulin × free fatty acids [FFAs]) in youth across the spectrum of adiposity from normal weight to obese and the spectrum from normal glucose tolerance (NGT) to impaired glucose tolerance (IGT) to type 2 diabetes, 2) the relationship of Adipose-IR with physical and metabolic characteristics, and 3) the predictive power of Adipose-IR for determining dysglycemia in youth.

RESEARCH DESIGN AND METHODS

A total of 205 youth had fasting glucose, insulin, FFA, Adipose-IR, body composition, visceral adipose tissue (VAT), leptin, and adiponectin evaluated.

RESULTS

Adipose-IR was 2.2-fold higher in obese NGT, 4.3-fold higher in IGT, and 4.6-fold higher in type 2 diabetes compared with that in normal-weight peers (all P < 0.05). Females with dysglycemia (IGT and type 2 diabetes) had higher Adipose-IR than their male counterparts (P < 0.001). Adipose-IR correlated positively with total body and visceral adiposity, fasting glucose, HOMA-IR, and leptin and negatively with adiponectin. Receiver operating characteristic curve analysis yielded an optimal cutoff for Adipose-IR of 9.3 μU/mL × mmol/L for determining dysglycemia with 80% predictive power.

CONCLUSIONS

Adipose-IR is a simple surrogate estimate that reflects pathophysiological alterations in adipose tissue insulin sensitivity in youth, with progressive deterioration from normal weight to obese and from NGT to IGT to type 2 diabetes. Adipose-IR can be applied in large-scale epidemiological/observational studies of the natural history of youth-onset type 2 diabetes and its progression or reversal with intervention strategies.

Waist Circumference and All-Cause Mortality among Older Adults in Rural Indonesia

Waist circumference, a measure of abdominal obesity, is associated with all-cause mortality in general adult population. However, the link between abdominal obesity with all-cause mortality in the studies of older adults is unclear. This study aims to determine the association between waist circumference and all-cause mortality in older adults in Indonesia. The association between waist circumference and all-cause mortality was examined in 10,997 men and women aged 50 years and older, in the World Health Organization (WHO) and International Network of field sites for continuous Demographic Evaluation of Populations and their Health in developing countries (INDEPTH) collaboration Study on global AGEing and adult health (SAGE) in Purworejo District Central Java, Indonesia during 2007⁻2010. Multivariate Cox regression analysis with restricted cubic splines was used to assess the non-linear association between waist circumference and all-cause mortality. During the 3-year follow-up, a total of 511 men and 470 women died. The hazard ratio plot shows a pattern of U-shape relationship between waist circumference and all-cause mortality among rich women, though the result was significant only for women in the lower end of waist circumference distribution (p < 0.05). Poor men with a low waist circumference (5th percentile) have a two times higher mortality risk (HR = 2.1; 95% CI = 1.3, 3.3) relative to those with a waist circumference of 90 cm. Poor women with a low waist circumference (25th percentile) have a 1.4 times higher mortality risk (HR = 1.4; 95% CI = 1.1, 1.8) relative to those with a waist circumference of 80 cm. This study shows a significant association between low waist circumference measure and mortality, particularly among poor men and women. Though the association between large waist circumference and mortality was not significant, we observed a trend of higher mortality risk particularly among rich women with large waist circumference measure. Public health intervention should include efforts to improve nutritional status among older people and promoting healthy lifestyle behaviours including healthy food and active lifestyle.

Vitamin D supplementation and body fat mass: a systematic review and meta-analysis

Studies have indicated that 25-hydroxyvitamin D (25(OH)D) level in obese is lower than normal weight subjects; however, results of studies that investigated relationship between 25(OH)D and fat mass are inconsistent. In addition, several randomized clinical trials (RCTs) have studied the influence of cholecalciferol supplement on percentage fat mass (PFM) but their results are conflicting. The objectives were to investigate the association between vitamin D3 and PFM pooling together observational studies and RCTs. PubMed/MEDLINE, Cochrane, and Scopus were comprehensively searched from inception to September 2016. The Fisher's Z (SE) of correlation coefficient and mean (SD) of changes in PFM from baseline were used to perform meta-analysis in observational studies and RCTs, respectively. To determine potential source of heterogeneity, subgroup and meta-regression analyses were conducted. Pooling correlation coefficients showed an inverse association between PFM (Fisher's Z: - 0.24, 95% CI: - 0.30 to -0 .18) and FM (Fisher's Z: - 0.32, 95% CI: - 0.43 to - 0.22) and 25(OH)D. Subgroup analysis revealed continent but not gender influence on the effect size. Meta-regression analysis indicated that age, latitude, and longitude are not sources of heterogeneity. Combining trials showed vitamin D3 supplementation had a mild but insignificant effect on PFM (- 0.31%, 95% CI: - 1.07 to 0.44). Subgroup analyses indicated that type of cholecalciferol and treatment regimens explain source of heterogeneity. Age, baseline body mass index, dose of cholecalciferol, length of study, female (%), and baseline 25(OH)D are not source of heterogeneity. In conclusion, our results state that 25(OH)D level is inversely correlated with PFM but cholecalciferol supplementation had no effect on PFM.

Impaired Lipolysis, Diminished Fat Oxidation, and Metabolic Inflexibility in Obese Girls With Polycystic Ovary Syndrome

Context

Metabolic flexibility reflects the ability to switch from lipid to carbohydrate oxidation during insulin stimulation manifested in increased respiratory quotient (RQ). Little is known about adipose tissue metabolism and metabolic flexibility in adolescent girls with polycystic ovary syndrome (PCOS).

Objective

We investigated whole-body lipolysis, substrate oxidation, and metabolic flexibility in obese girls with PCOS vs obese girls without PCOS.

Patients/Design

Twenty-one obese girls with PCOS and 21 obese girls without PCOS were pair-matched for age and race. Body composition, abdominal visceral adipose tissue (VAT), sex hormones, lipid profile, and adiponectin were measured. Whole-body lipolysis ([2H5]glycerol turnover), RQ, and substrate oxidation (indirect calorimetry) were evaluated during fasting and a hyperinsulinemic-euglycemic clamp together with assessment of insulin sensitivity (IS).

Results

Despite similar body mass index and percent body fat, girls with PCOS vs girls without PCOS had lower fasting lipolysis and fat oxidation, less increase in RQ during hyperinsulinemia with impaired suppression in lipolysis and lipid oxidation, and lower IS. In multiple regression, the best predictors of metabolic flexibility were [using clinical parameters: adiponectin, fasting triglycerides, and insulin (R2 = 0.618, P < 0.0001); using research parameters: IS, VAT, and baseline RQ (R2 = 0.756, P < 0.0001)].

Conclusions

Obese girls with PCOS vs obese girls without PCOS have decreased lipid mobilization, diminished fat oxidation, and metabolic inflexibility. Whether this metabolic phenotype of adipose tissue dysfunction, which is conducive to fat accretion, plays a role in the induction and maintenance of obesity in adolescent girls with PCOS remains to be determined.

Accelerometer-determined peak cadence and weight status in children from São Caetano do Sul, Brazil

The purpose of this study was to determine the relationship between peak cadence indicators and body mass index (BMI) and body fat percentage (BF%)-defined weight status in children. The sample comprised 485 Brazilian children. Minute-by-minute step data from accelerometry were rank ordered for each day to identify the peak 1-minute, 30-minute and 60-minute cadence values. Data were described by BMI-defined and bioelectrical impedance-determined BF% weight status. BMI-defined normal weight children had higher peak 1-minute (115.5 versus 110.6 and 106.6 steps/min), 30-minute (81.0 versus 77.5 and 74.0 steps/min) and 60-minute cadence (67.1 versus 63.4 and 60.7 steps/min) than overweight and obese children (p<.0001), respectively. Defined using %BF, normal weight children had higher peak 1-minute (114.5 versus 106.1 steps/min), 30-minute (80.4 versus 73.1 steps/min) and 60-minute cadence (66.5 versus 59.9 steps/min) than obese children (p<.0001). Similar relationships were observed in boys; however, only peak 1- minute cadence differed significantly across BMI and %BF-defined weight status categories in girls. Peak cadence indicators were negatively associated with BMI and BF% in these schoolchildren and significantly higher among normal weight compared to overweight or obese children.

Anti-Müllerian Hormone in Obese Adolescent Girls With Polycystic Ovary Syndrome

PURPOSE

Anti-Müllerian hormone (AMH) is proposed as a biomarker of polycystic ovary syndrome (PCOS). This study investigated: (1) AMH concentrations in obese adolescents with PCOS versus without PCOS; (2) the relationship of AMH to sex steroid hormones, adiposity, and insulin resistance; and (3) the optimal AMH value and the multivariable prediction model to determine PCOS in obese adolescents.

METHODS

AMH levels were measured in 46 obese PCOS girls and 43 obese non-PCOS girls. Sex steroid hormones, clamp-measured insulin sensitivity and secretion, body composition, and abdominal adiposity were evaluated. Logistic regression and receiver-operating characteristic curve analyses were used, and multivariate prediction models were developed to test the utility of AMH for the diagnosis of PCOS.

RESULTS

AMH levels were higher in obese PCOS versus non-PCOS girls (8.3 ± .6 vs. 4.3 ± .4 ng/mL, p < .0001), of comparable age and puberty. AMH concentrations correlated positively with age in both groups, total and free testosterone in PCOS girls only, abdominal adipose tissue in non-PCOS girls, with no correlation to in vivo insulin sensitivity and secretion in either groups. A multivariate model including AMH (cutoff 6.26 ng/mL, area under the curve .788) together with sex hormone-binding globulin and total testosterone exhibited 93.4% predictive power for diagnosing PCOS.

CONCLUSIONS

AMH may be a useful biomarker for the diagnosis of PCOS in obese adolescent girls.

Adiponectin gene variants and abdominal obesity in an Iranian population

INTRODUCTION

Waist-to-height ratio (WHtR) can be effective for the diagnosis of abdominal obesity and the risk of type 2 diabetes. The role of genetic factors in the development of obesity has been broadly recognized. Adiponectin's level is inversely correlated with body fat percentage and is reduced in obesity and type 2 diabetes. The aim of this study is to investigate the association between WHtR and adiponectin gene polymorphisms in Iranian population.

METHODS

This study was conducted on 610 subjects from two Iranian populations. Anthropometric characteristics were measured by routine methods. Blood samples were collected in tubes (3-5 mL) containing EDTA and were stored at 20 °C. After DNA extraction, genotyping was performed using PCR-RFLP technique.

RESULTS

There were statistically significant differences in genotype frequencies of -11391 G/A in centrally obese (WHtR >0.5) and noncentrally obese (WHtR ≤0.5) subjects (P value <0.044). In the former, the frequencies of GG and GA + AA genotypes were 89.4 and 10.6 %, respectively, while the frequencies of GG and GA + AA genotypes were 95.9 and 4.1 %, respectively, in noncentrally obese subjects.

CONCLUSIONS

The frequency of GG genotype was significantly increased in subjects with WHtR >0.5 compared to the other group. After adjustment for diabetes, abdominal obesity was significantly associated with the -11391 G/A polymorphism.

Differences in β-cell function and insulin secretion in Black vs. White obese adolescents: do incretin hormones play a role?

Black youth are at higher risk for type 2 diabetes (T2D) than their White peers. Previously we demonstrated that for the same degree of insulin sensitivity, Black youth have an upregulated β-cell function and insulin hypersecretion, in response to intravenous (iv) glucose, compared with Whites. To investigate if the same holds true during an oral glucose challenge and because of the important role of glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) in augmenting insulin secretion, we examined β-cell function and incretin hormones in 85 Black and 78 White obese adolescents, with normal glucose tolerance (NGT), during a 2-h oral glucose tolerance test (OGTT) with mathematical modeling of plasma glucose and C-peptide concentrations to assess β-cell glucose sensitivity (βCGS), rate sensitivity, potentiation factor, and insulin sensitivity. Incretin, pancreatic polypeptide, and glucagon concentrations were measured during the OGTT. Black obese youth had a heightened early insulin secretion together with significantly greater βCGS, rate sensitivity, and potentiation factor compared with Whites, with no differences in incretin and glucagon concentrations. Basal and stimulated insulin clearance was lower (p = 0.001) in Black vs. White youth. In conclusion, during an OGTT Black obese youth with NGT demonstrate a pronounced early insulin secretion jointly with heightened β-cell glucose sensitivity, rate sensitivity, and potentiation factor. These racial disparities in β-cell function and the pathophysiological components of T2D are unlikely to be attributed to incretin hormones and remain to be investigated further to explain the metabolic basis for the enhanced risk of T2D in back youth.

Dexa Body Composition Assessment in 10-11 Year Healthy Children

INTRODUCTION

Obesity is a growing health problem associated with metabolic derangements and cardiovascular disease. Accumulating evidence links the accumulation of visceral adipose tissue (VAT) to these obesity related health risks in adults. Childhood obesity is associated with a lifetime risk of cardiovascular disease and poses a serious challenge to future health care. In children, there is much less data on the prevalence and gender differences of visceral obesity than in adults. This study aims to provide reference values for VAT in children 10-11 years of age.

METHODS

In a cross-sectional study performed in the north western part of theNetherlands, healthy children of 10-11 years of age, were recruited from primary schools. Anthropometric data consisting of height, weight, waist circumference (WC) and BMI were measured. Body composition was measured using DXA, providing measures for bone mineral content, total fat mass (TFM), lean body mass (LBM) and VAT.

RESULTS

217 children were eligible for this study. Girls appeared to have a greater TFM (31.4% vs 27.5% of total body weight (TBW); P < .01) but lower VAT (0.3% vs 0.5% of TBW;P < .01) than boys, whereas boys had higher LBM (65.4% vs 69.3% TBW;P < .01). Median VAT area (cm2) was 41.1 for boys and 22.4 for girls (P < .01). Moderate to strong correlations were found for WC and BMI with VAT (boys: r = .664 and r = .630; Girls r = .699 and r = .546 respectively all P < .001).

DISCUSSION

This study shows gender specific differences in VAT percentiles in healthy non-obese 10-11 year old children as measured by DXA that may serve as reference values in children. Independent of BMI and WC, girls tend to have more TFM but less VAT and LBM than boys.

The association of visceral adipose tissue and subcutaneous adipose tissue with metabolic risk factors in a large population of Chinese adults

OBJECTIVE

Abdominal visceral (VAT) and subcutaneous (SAT) adipose tissues contribute to obesity, but may have different cardiometabolic risk profiles. We examined and compared the associations of abdominal VAT and SAT with metabolic risk factors in a large cohort of Chinese adults.

METHODS

This study was based on cross-sectional analysis of data from 1449 adults aged 40-65 years. VAT and SAT were assessed at L4-L5 level by magnetic resonance imaging. The associations of VAT and SAT with blood pressure, glucose and lipid were examined by linear regression stratified by sex and glucose tolerance status (normal glucose tolerance and prediabetes). Logistic regression was used to analyse the association of VAT and SAT with risk of hypertension, prediabetes and dyslipidaemia.

RESULTS

VAT was more strongly associated with metabolic risk factors. Higher VAT was associated with higher blood pressure (βmen = 3·99, P = 0·0002; βwomen = 6·46, P = 0·0002), higher triglyceride (βmen = 0·45, P < 0·0001; βwomen = 0·6, P < 0·0001), higher total cholesterol (βmen = 0·15, P = 0·02; βwomen = 0·37, P = 0·0002) and higher 2-h glucose levels (βmen = 0·68, P = 0·003; βwomen = 0·94, P < 0·0001). The association remained significant after subjects were stratified by glucose tolerance status. However, SAT was not associated with any additional risk factors. VAT was associated with increased risk of hypertension (OR = 1·97, P < 0·0001), prediabetes (OR = 1·53, P = 0·0007) and dyslipidaemia (OR = 2·40, P < 0·0001). These associations were not observed for SAT.

CONCLUSIONS

VAT was more strongly associated with cardiometabolic risk factors than SAT in a large cohort of Chinese adults. Higher VAT was associated with increased risk of hypertension, dyslipidaemia and prediabetes.

Role of waist measures in addition to body mass index to assess the hypertension risk in children

AIM

This study aimed to evaluate whether waist measures, including waist circumference (WC) and waist-to-height ratio (WHtR), can improve the ability of body mass index (BMI) to assess the hypertension risk when used as continuous variables.

METHODS

In this cross-sectional study, 82 432 Chinese children aged 9-17 years were included. Elevated BP was defined using age-sex-and-height-specific references. Logistic regression model and area under the receiver operating characteristic curve (AUC) were performed after BMI and waist measures were converted into age-and-sex-based z-scores.

RESULTS

WHtR, but not WC, was associated with elevated BP after adjusting for BMI, with the odds ratios ranging between 1.14 (95% confidence interval: 1.04, 1.25) and 1.30 (1.21, 1.39) for one unit increase in WHtR z-score. Combined use of BMI and WHtR z-scores showed a significantly larger AUC than BMI alone (p < 0.05), while joint use of BMI and WC was not better than BMI alone.

CONCLUSION

WHtR, rather than WC, provided further information on hypertension risk beyond that provided by BMI alone when used as a continuous variable. This study suggests WHtR, in addition to BMI, should be included for the assessment of childhood adiposity in routine paediatric practice.

Distinguishing characteristics of metabolically healthy versus metabolically unhealthy obese adolescent girls with polycystic ovary syndrome

OBJECTIVE

To investigate the key physical, metabolic, hormonal and cardiovascular characteristics of metabolically healthy obese (MHO) versus unhealthy obese (MUHO) girls with polycystic ovary syndrome (PCOS).

DESIGN

Cross-sectional study.

SETTING

Research center.

PATIENT(S)

Seventy obese girls with PCOS were divided into 19 MHO and 51 MUHO based on cutoff points for in vivo insulin sensitivity (within and < 2 SDs of the mean of the insulin sensitivity of the normal-weight girls, respectively).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Body composition, abdominal fat, in vivo insulin sensitivity and secretion (hyperinsulinemic-euglycemic and hyperglycemic clamps respectively), hormonal profile, and cardiovascular disease risk markers.

RESULT(S)

MUHO-PCOS girls had higher waist circumference, visceral adipose tissue, leptin, and free testosterone, lower SHBG and E2, higher non-high-density lipoprotein (HDL) cholesterol and atherogenic lipoprotein particle concentrations, smaller HDL particle size, and higher high-sensitivity C-reactive protein compared with MHO-PCOS girls. Hepatic and peripheral insulin sensitivity were lower with higher first- and second-phase insulin secretion, but β-cell function relative to insulin sensitivity was lower in MUHO versus MHO. Pair matching of MHO and MUHO regarding age and body mass index revealed similar findings. MUHO-PCOS girls had larger visceral adiposity, lower insulin sensitivity and β-cell function, worse hormonal profile, and severely atherogenic lipoprotein concentrations compared with MHO-PCOS girls.

CONCLUSION(S)

MHO-PCOS girls have favorable physical, metabolic, hormonal, and cardiovascular disease (CVD) characteristics and lower risk biomarkers for type 2 diabetes compared with their MUHO-PCOS peers. A greater understanding of the contrast in this risk phenotype in obese girls with PCOS may have important implications for therapeutic interventions, their outcomes, and their durability.

Abdominal fat depots associated with insulin resistance and metabolic syndrome risk factors in black African young adults

Background

Individuals of black African ethnicity tend to have less visceral adipose tissue (VAT) but more subcutaneous-abdominal adipose tissue (SCAT) than white Caucasians. However, it is unclear whether such distribution of abdominal fat is beneficial for metabolic disease risk in black individuals. Here we compared the associations between these specific abdominal fat depots, insulin sensitivity and metabolic syndrome risk.

Methods

A cross-sectional analysis of 76 black South African young adults (36 men; 40 women) aged 18–19 years participating in the Birth to Twenty Cohort Study had VAT and SCAT measured by MRI. The metabolic syndrome traits (blood pressure, lipid profile, fasting glucose and insulin) were measured and the values were combined into a metabolic syndrome risk score. Fasting glucose and insulin were used to derive the HOMA-index of insulin resistance (HOMA-IR).

Results

Compared to men, women had greater VAT (mean: 16.6 vs. 12.5 cm²) and SCAT (median 164.0 vs. 59.9 cm²). In men, SCAT (r = 0.50) was more strongly correlated to the metabolic syndrome score (MetS) than was VAT (r = 0.23), and was associated with both MetS (P = 0.001) and HOMA-IR (P = 0.001) after adjustment for VAT and total fat mass. In women, both abdominal fat compartments showed comparable positive correlations with MetS (r = 0.26 to 0.31), although these trends were weaker than in men.

Conclusions

In young black South African adults, SCAT appears to be more relevant than VAT to metabolic syndrome traits.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-015-2147-x) contains supplementary material, which is available to authorized users.

Abdominal Fat Distribution and Cardiovascular Risk in Men and Women With Different Levels of Glucose Tolerance

CONTEXT

Regional fat distribution rather than overall obesity has been recognized as important to understanding the link between obesity and cardiovascular disease.

OBJECTIVE

We examined the associations of abdominal visceral adipose tissue (VAT) and abdominal subcutaneous adipose tissue (SAT) with cardiovascular risk factors in a Caucasian population of men and women with normal glucose tolerance, prediabetes, or screen-detected diabetes.

DESIGN, SETTING, AND PARTICIPANTS

The study was based on cross-sectional analysis of data from 1412 adults age 45-80 years. VAT and SAT were assessed by ultrasound. The associations of VAT and SAT with blood pressure and lipids were examined by linear regression analysis adjusted for age, sex, smoking, alcohol, physical activity, glucose tolerance status (GTS), medication use, and body mass index. Effect modification by GTS and sex was examined, and stratified analyses performed.

RESULTS

Independent of SAT and overall obesity, VAT was associated with higher triglyceride and lower high-density lipoprotein (HDL) cholesterol levels in both men and women and additionally associated with higher total cholesterol in men. SAT was independently associated with higher total cholesterol and low-density lipoprotein cholesterol levels in both sexes, and SAT was additionally associated with higher triglyceride and lower HDL cholesterol levels in women and with higher blood pressure in participants with diabetes.

CONCLUSION

Both abdominal VAT and SAT are independent of overall obesity associated with cardiovascular risk in a population of men and women at low to high risk of diabetes or with screen-detected diabetes.

Elevated neck circumference and associated factors in adolescents

Background

Upper body subcutaneous fat, estimated by neck circumference (NC), may present greater metabolic risk than visceral fat. The aim of this study was to determine cutoff values for NC in adolescents that identify overweight and obesity, the prevalence of elevated NC, and its association with associated factors.

Methods

Cross-sectional study with adolescents from public schools in São Paulo. Anthropometric variables, blood pressure and pubertal stage were collected. Cutoff values for NC were determined by Receiver Operating Characteristic curves. A binary logistic regression was used to determine relationships between NC and associated factors.

Results

Among 1668 adolescents studied, 54.92% were female. The cutoff values of NC in girls and boys that identified overweight were 31.25 and 34.25 cm, and obesity, 32.65 and 37.95 cm, respectively, and the prevalence of adolescents with high NC was 32.63% in females and 37.63% among males. NC for overweight was observed that there was an association with sex, weight, body mass index, arm, waist and thigh circumferences, pubertal stages and body fat percent (BF%). NC for obesity was found association with gender, weight, arm and thigh circumferences, and BF% (p < 0.001).

Conclusion

It was concluded that there is high prevalence of elevated NC and higher risks for this outcome considering overweight and obesity, sex, weight, arm and thigh circumferences, BF%, besides being an easy and simple measure for use in clinical practice.

The Relation between Visceral and Subcutaneous Fat to Bone Mass among Egyptian Children and Adolescents

BACKGROUND: The relation between fat distribution and bone mass is still being debated in children and adolescents.AIM: To verify the influence of both visceral and subcutaneous fat on bone mass among Egyptian children and adolescents.SUBJECTS AND METHODS: The study involved 78 (38 boys and 40 girls) individuals from children (42) and adolescents (36), aged 8-17 years. They were divided into 2 age groups: children group (20 boys and 22 girls) aged 8-12 years and adolescent group (18 boys and 18 girls) aged 13-17 years. Anthropometric measurements, visceral and subcutaneous fat (measured by ultrasound), body composition, BMD and BMC (Measured by DXA), were attempted.RESULTS: Among children, significant positive correlations between visceral fat; in males; and subcutaneous fat; in females; with total BMC, BMD and its Z-score were revealed. After exclusion of age effect, the association between visceral fat in females with total BMD and its Z-score and lumbar BMD-Z-score became significant.  For adolescents, no correlation was observed between either visceral or subcutaneous fat with any parameter of bone mass.CONCLUSIONS: Visceral and subcutaneous fat had significant positive association with bone mass in children; males and females respectively. On the contrary such association disappeared during adolescence.

β-cell function, incretin effect, and incretin hormones in obese youth along the span of glucose tolerance from normal to prediabetes to type 2 diabetes

Using the hyperglycemic and euglycemic clamp, we demonstrated impaired β-cell function in obese youth with increasing dysglycemia. Herein we describe oral glucose tolerance test (OGTT)-modeled β-cell function and incretin effect in obese adolescents spanning the range of glucose tolerance. β-Cell function parameters were derived from established mathematical models yielding β-cell glucose sensitivity (βCGS), rate sensitivity, and insulin sensitivity in 255 obese adolescents (173 with normal glucose tolerance [NGT], 48 with impaired glucose tolerance [IGT], and 34 with type 2 diabetes [T2D]). The incretin effect was calculated as the ratio of the OGTT-βCGS to the 2-h hyperglycemic clamp-βCGS. Incretin and glucagon concentrations were measured during the OGTT. Compared with NGT, βCGS was 30 and 65% lower in youth with IGT and T2D, respectively; rate sensitivity was 40% lower in T2D. Youth with IGT or T2D had 32 and 38% reduced incretin effect compared with NGT in the face of similar changes in GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) in response to oral glucose. We conclude that glucose sensitivity deteriorates progressively in obese youth across the spectrum of glucose tolerance in association with impairment in incretin effect without reduction in GLP-1 or GIP, similar to that seen in adult dysglycemia.

Relationship of anthropometric indices to abdominal and total body fat in youth: sex and race differences

OBJECTIVE

To determine the influence of sex and race on relationships between anthropometry (body mass index [BMI], waist circumference [WC], waist-to-height ratio [W/Ht]) and adiposity (fat mass [FM], abdominal subcutaneous [SAT] and visceral adipose tissue [VAT]) in African American and white youth.

METHODS

The sample included 382 youth 5-18 years of age. FM and abdominal adiposity were assessed using dual energy X-ray absorptiometry and magnetic resonance imaging. Regression was used to examine sex and race effects in the relationship between independent (BMI, WC, and W/Ht) and dependent (FM, SAT and VAT) variables.

RESULTS

BMI and WC were highly related to adiposity while W/Ht was moderately related. The association of BMI with FM and SAT was independent of sex and race, while the relationships of WC and W/Ht with FM and SAT were influenced by both sex and race. In contrast, the association between BMI and VAT was influenced by sex and race, while the relationships of WC and W/Ht with VAT were not.

CONCLUSIONS

WC and W/Ht have similar relationships with adiposity; however, WC presented stronger relationships. BMI is a predictor of overall adiposity but sex and race play a role in its relationship with VAT.

Polycystic ovary syndrome and nonalcoholic fatty liver in obese adolescents: association with metabolic risk profile

OBJECTIVE

To investigate the relationship between liver fat and in vivo insulin sensitivity, body composition, abdominal adiposity, and lipid metabolism in obese adolescent girls with polycystic ovary syndrome (PCOS).

DESIGN

Cross-sectional case-control study.

SETTING

Research center.

PATIENT(S)

Thirty Tanner stage V obese girls with PCOS.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Liver fat, abdominal adiposity, in vivo insulin-stimulated glucose disposal, whole-body lipolysis, fat oxidation, lipoprotein particle size and concentration, and liver enzymes (alanine aminotransferase and aspartate aminotransferase). Fatty liver index <1 is indicative of fatty liver.

RESULT(S)

Fatty liver was present in 6.7% of the individuals (6.7%). Levels of alanine aminotransferase and aspartate aminotransferase were not different between those with fatty liver vs. without. Fatty liver index was associated with age (r = -0.53), body mass index (r = -0.41), total (r = -0.43) and subcutaneous (r = -0.41) abdominal adiposity, insulin-stimulated glucose disposal (r = 0.36), and small, medium small, and very small low-density lipoprotein concentrations (r ≥ -0.43). In a multiple regression analysis, age, total T, race, and insulin-stimulated glucose disposal explained 43% of the variance (R(2) = 0.43) in fatty liver index, with age (R(2) = 0.28) and total T (R(2) = 0.11) being independent contributors.

CONCLUSION(S)

Liver fat is associated with increasing age, even in the narrow adolescent age range, increasing abdominal adiposity, worsening insulin sensitivity, and dyslipoproteinemia in obese adolescent girls with PCOS. Targeting these abnormalities early in the course of PCOS may halt future nonalcoholic fatty liver disease in adulthood.

Reproducibility of ultrasonography for assessing abdominal fat distribution in a population at high risk of diabetes

Background:

Visceral fat plays an important role in the development of metabolic disease independently of the effect of overall abdominal fat. Ultrasonography is an accessible method of accurately assessing abdominal fat distribution in epidemiological studies, but few details about the reproducibility of this method have been published.

Objective:

The aim of this study was to investigate the reproducibility of ultrasonography in the assessment of abdominal fat distribution in a population at high risk of type 2 diabetes.

Design and Methods:

Ultrasonography was used to estimate visceral and subcutaneous abdominal fat. Intra- and interobserver variation, short-term variation and variation between estimates in the fasting and non-fasting state were examined in three samples of 30, 33 and 23 participants from the ADDITION-PRO study. A variance components model was used to calculate intra- and interobserver variation, and Bland–Altman plots were drawn for all three substudies.

Results:

Coefficients of variation for intra- and interobserver variation were in the range 3.4–6.1%, except for interobserver variation for subcutaneous fat (9.5%). Short-term variation over a median of 35 days had a coefficient of variation of 15%. The effect of a meal was primarily on the visceral estimates and did not extend beyond the first postprandial hour. Non-fasting visceral estimates were larger than fasting estimates.

Conclusion:

Both visceral and subcutaneous fat can be estimated with ultrasonography with adequate intra- and interobserver reproducibility by clinical researchers with limited training, making it a feasible method of assessing abdominal fat distribution in epidemiological studies.

25-Hydroxyvitamin D in obese youth across the spectrum of glucose tolerance from normal to prediabetes to type 2 diabetes

OBJECTIVE

To 1) determine if plasma 25-hydroxyvitamin D (25[OH]D) concentrations differ among obese youth with normal glucose tolerance (NGT) versus prediabetes versus type 2 diabetes and 2) assess the relationships between 25(OH)D and in vivo insulin sensitivity and β-cell function in this cohort.

RESEARCH DESIGN AND METHODS

Plasma 25(OH)D concentrations were examined in banked specimens in 9- to 20-year-old obese youth (n = 175; male 42.3%, black 46.3%) (NGT, n = 105; impaired glucose tolerance [IGT], n = 43; type 2 diabetes, n = 27) who had in vivo insulin sensitivity and secretion measured by hyperinsulinemic-euglycemic and hyperglycemic clamp techniques and had an assessment of total body composition and abdominal adiposity.

RESULTS

The mean age and BMI of the subjects were 14.3 ± 2.1 years and 35.7 ± 5.6 kg/m(2), respectively. BMI, plasma 25(OH)D, and the proportion of vitamin D-deficient and -insufficient children did not differ across the three groups. Furthermore, there was no association between 25(OH)D and in vivo insulin sensitivity or β-cell function relative to insulin sensitivity (disposition index) in all groups combined or in each group separately.

CONCLUSIONS

Our data in obese youth show 1) no differences in plasma 25(OH)D concentrations across the glucose tolerance groups and 2) no relationship between 25(OH)D and in vivo insulin sensitivity and β-cell function relative to insulin sensitivity in any of the groups. It remains uncertain if enhancement of the vitamin D status could improve pathophysiological mechanisms of prediabetes and type 2 diabetes in obese youth.

Waist circumference measurement site does not affect relationships with visceral adiposity and cardiometabolic risk factors in children

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

A number of anatomic sites are used for the measurement of waist circumference. A number of studies have documented differences in the absolute values of waist circumference measurements across these common sites in adults. It is unclear whether waist circumference measurement site alters the relationship with abdominal adiposity and cardiometabolic risk factors in children.

WHAT THIS STUDY ADDS

The absolute values of waist circumference at four anatomic locations (minimal, midway, iliac, umbilicus) differed and this affected prevalence of high (≥90th percentile) waist circumference. The relationships between waist circumference values at four anatomic locations and both depot-specific adiposity and cardiometabolic risk factors were similar across race and sex groups.

BACKGROUND

Different waist circumference (WC) measurement sites are used in clinical and epidemiological settings.

OBJECTIVES

To examine differences in WC measurement at four anatomic sites and how each WC measurement relates to visceral adipose tissue (VAT) and cardiometabolic risk factors in children.

METHODS

A total of 371 white and African-American children aged 5 to 18 years had WC measured at four sites: minimal waist, midpoint between the iliac crest and the lowest rib, superior border of the iliac crest and the umbilicus. Abdominal VAT was measured using magnetic resonance imaging and cardiometabolic risk factors were defined using National Heart, Lung and Blood Institute guidelines. Relationships between WC sites and VAT and risk factors were explored in each race-by-sex group.

RESULTS

All WC sites were highly correlated (r = 0.97 to 0.99). Differences in absolute mean WC values existed in all race-by-sex groups, and this affected the prevalence of high WC (≥90th percentile). Values were lowest for minimal waist and highest for umbilicus. Age-controlled partial correlations between WC and logVAT VAT were 0.81-0.89 (all P < 0.001) and between WC and cardiometabolic risk factors were -0.24 to -0.41 and 0.19 to 0.52 (all P < 0.05).

CONCLUSIONS

  While the absolute values of WC at four anatomic locations differed, the relationships between WC values and both VAT and cardiometabolic risk factors were similar within all race-by-sex groups.

Ethnic and sex differences in visceral, subcutaneous, and total body fat in children and adolescents

OBJECTIVE

This study investigated ethnic and sex differences in the distribution of fat during childhood and adolescence.

DESIGN AND METHODS

A cross-sectional sample (n = 382), aged 5-18 years, included African American males (n = 84), White males (n = 96), African American females (n = 118), and White females (n = 84). Measures for total body fat (TBF) mass and abdominal adipose tissue (total volume and L4-L5 cross-sectional area) for both subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) depots were assessed by dual-energy X-ray absorptiometry and magnetic resonance image, respectively. Analyses of covariance (ANCOVAs) were used to determine ethnic and sex differences in TBF (adjusted for age) and ethnic and sex differences in SAT and VAT (adjusted for both age and TBF).

RESULTS

Age-adjusted TBF was greater in African Americans (P = 0.017) and females (P < 0.0001) compared with Whites and males, respectively. In age- and TBF-adjusted ANCOVAs, no differences were found in the SAT. The VAT volume was, however, greater in Whites (P < 0.0001) and males (P < 0.0001) compared with African Americans and females, respectively. Similar patterns were observed in SAT and VAT area at L4-L5.

CONCLUSIONS

The demonstrated ethnic and sex differences are important confounders in the prevalence of obesity and in the assignment of disease risk in children and adolescents.

Maturity-associated variation in total and depot-specific body fat in children and adolescents

OBJECTIVES

This study considered the association between sexual maturation and adiposity in children and adolescents, and examined the contribution of sexual maturation to ethnic differences in total and depot-specific body fat.

METHODS

The sample included 382 White and African American 5-18-year-olds. Body mass index (BMI), waist circumference (WC) and sexual maturity status (breast/genital and pubic hair stage) were assessed in a clinical setting. Total body fat (TBF) was measured by dual-energy X-ray absorptiometry and abdominal subcutaneous (SAT) and visceral adipose tissue (VAT) were measured by magnetic resonance imaging. Analysis of covariance adjusted for age was used to examine the association between sexual maturity status and adiposity, and linear regression adjusted for age was used to examine the influence of sexual maturation on ethnic differences in adiposity. Analysis of VAT also controlled for TBF. Significance was accepted at P < 0.05.

RESULTS

Breast/genital stage was significantly associated with BMI, WC, TBF, and SAT in girls of both ethnic groups and in White boys. Breast stage was associated with VAT. Stage of pubic hair was significantly associated with TBF and VAT in White girls only. In girls, sexual maturation attenuated the ethnic effects on BMI and WC, but the ethnic effect in VAT persisted. In boys, sexual maturation did not attenuate ethnic differences on VAT and did not predict WC or SAT. Sexual maturity status independently explained variance in adiposity in girls only.

CONCLUSIONS

Sexual maturity status is an important determinant of pediatric adiposity and attenuates ethnic differences in girls' adiposity.

Adiposity in children and adolescents: correlates and clinical consequences of fat stored in specific body depots

The 2011 Pennington Biomedical Research Center's Scientific Symposium focused on adiposity in children and adolescents. The symposium was attended by 15 speakers and other invited experts. The specific objectives of the symposium were to (i) integrate the latest published and unpublished findings on the laboratory and clinical assessment of depot-specific adiposity in children and adolescents, (ii) understand the variation in depot-specific adiposity and related health outcomes associated with age, sex, maturation, ethnicity and other factors and (iii) identify opportunities for incorporating new markers of abdominal obesity into clinical practice guidelines for obesity in children and adolescents. This symposium provided an overview of important new advances in the field and identified directions for future research. The long-term goal of the symposium is to aid in the early identification of children and adolescents who are at increased health risk because of obesity and obesity-related conditions.

Ethnic and sex differences in body fat and visceral and subcutaneous adiposity in children and adolescents

Body fat and the specific depot where adipose tissue (AT) is stored can contribute to cardiometabolic health risks in children and adolescents. Imaging procedures including magnetic resonance imaging and computed tomography allow for the exploration of individual and group differences in pediatric adiposity. This review examines the variation in pediatric total body fat (TBF), visceral AT (VAT) and subcutaneous AT (SAT) due to age, sex, maturational status and ethnicity. TBF, VAT and SAT typically increase as a child ages, though different trends emerge. Girls tend to accumulate more TBF and SAT during and after puberty, depositing fat preferentially in the gynoid and extremity regions. In contrast, pubertal and postpubertal boys tend to deposit more fat in the abdominal region, particularly in the VAT depot. Sexual maturation significantly influences TBF, VAT and SAT. Ethnic differences in TBF are mixed. VAT tends to be higher in white and Hispanic youth, whereas SAT is typically higher in African American youth. Asian youth typically have less gynoid fat but more VAT than whites. Obesity per se may attenuate sex and ethnic differences. Particular health risks are associated with high amounts of TBF, VAT and SAT, including insulin resistance, hepatic steatosis, metabolic syndrome and hypertension. These risks are affected by genetic, biological and lifestyle factors including physical activity, nutrition and stress. Synthesizing evidence is difficult as there is no consistent methodology or definition to estimate and define depot-specific adiposity, and many analyses compare SAT and VAT without controlling for TBF. Future research should include longitudinal examinations of adiposity changes over time in representative samples of youth to make generalizations to the entire pediatric population and examine variation in organ-specific body fat.

High-molecular-weight adiponectin and anthropometric variables among elementary schoolchildren: a population-based cross-sectional study in Japan

Background

Studies about the relationship between high-molecular-weight adiponectin (HMW-adn) and anthropometric variables among population-based elementary schoolchildren have been too limited, especially in Japan, where blood collection is not usually performed in the annual health examination at elementary schools. The objective of the present study was to investigate the relationship between HMW-adn and anthropometric variables (body mass index [BMI], percent body fat [%BF], waist circumference [WC], and waist-to-height ratio [WHtR]) among population-based elementary schoolchildren in Japan.

Methods

Subjects comprised all fourth-grade schoolchildren (9 or 10 years of age) in the town of Ina, Saitama Prefecture, Japan during 2005–2008 (N = 1675). After excluding 21 subjects because of refusal to participate or incomplete data, data from a total of 1654 subjects (846 boys and 808 girls) were analyzed. The height, weight, %BF, and WC of each subject were measured, while blood samples were drawn from the subjects to measure adiponectin levels (HMW-adn and total adiponectin). Childhood obesity was determined according to the age- and sex-specific cut-off points proposed by the International Obesity Task Force. Spearman’s correlation coefficients between adiponectin levels and anthropometric variables were calculated for each sex.

Results

The anthropometric variables were negatively correlated with HMW-adn in both boys and girls. Correlation coefficients of HMW-adn with anthropometric variables in the obesity group were consistently higher than those in the non-obesity group among both boys and girls. In addition, only WHtR was significantly correlated with HMW-adn regardless of sex and physique (obesity or non-obesity); the correlation coefficient was -0.386 among boys and -0.543 among girls in the obesity group, while it was -0.124 among boys and -0.081 among girls in the non-obesity group.

Conclusions

HMW-adn was negatively correlated with anthropometric variables, while the correlation coefficients of HMW-adn with anthropometric variables in the obesity group were consistently higher than those in the non-obesity group. Moreover, only WHtR was significantly associated with HMW-adn regardless of sex and physique. The results of this study suggested that it is useful to monitor WHtR as a surrogate for HMW-adn among elementary school students, especially obese children.

Distribution and association of hs-CRP with cardiovascular risk variables of metabolic syndrome in adolescent learners

OBJECTIVE

Metabolic syndrome (MetS) and its associated cardiovascular risk are on the increase in children. High-sensitivity C-reactive protein (hs-CRP) has emerged as a useful marker for inflammation associated with atherosclerosis and cardiovascular disease. Our aim was to determine the distribution of hs-CRP in an effort to identify the MetS variable that is critical in modulating plasma CRP levels in a population of South African adolescents.

DESIGN

A cross-sectional analytical study design was used for this investigation, where the dependent and independent variables were measured simultaneously.

METHODS

Anthropometric variables, blood pressure, fasting blood glucose and lipids were performed on 324 consenting learners aged 15-18 years from three different ethnic groups (Black, White and Coloured). The National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) for ages 15-18 year olds was used to define MetS.

RESULTS

The prevalence of MetS and obesity was 3.7% and 7.1%, respectively. The hs-CRP levels were significantly higher in subjects with a waist-circumference greater than the 90th percentile (p < 0.01) and in obese learners with MetS, but was lower in adolescents with normal weight and MetS. Median hs-CRP levels increased with an increasing number of metabolic abnormalities and exceeded 3 mg/L in 19% of adolescents. Gender and ethnic differences were observed.

CONCLUSION

Our findings suggest that obesity and waist circumference appear to be major mediators of hs-CRP levels in South African adolescents.

Type 2 diabetes in youth: are there racial differences in β-cell responsiveness relative to insulin sensitivity?

OBJECTIVE

Non-diabetic African American (AA) youth have an upregulated insulin secretion relative to insulin sensitivity (IS) compared with their American White (AW) peers. We investigated if similar racial differences exist in youth with T2DM.

RESEARCH DESIGN AND METHODS

Fourteen AAs and 14 AWs T2DM adolescents underwent evaluation of IS and clearance (hyperinsulinemic-euglycemic clamp), first- and second-phase insulin and C-peptide secretion (hyperglycemic clamp); body composition (DEXA); and abdominal adiposity (CT).

RESULTS

AA and AW T2DM had similar HbA1c, diabetes duration, BMI, and % body fat, with lower visceral fat in AAs (p = 0.013). While insulin-stimulated glucose disposal was similar in AA and AW (7.5 ± 1.0 vs. 7.3 ± 0.9 mg/kg FFM/min), IS tended to be lower (2.5 ± 0.4 vs. 3.8 ± 0.6 mg/kg FFM/min per µU/mL, p = 0.081). First-phase insulin (175.7 ± 52.9 vs. 66.6 ± 10.8 µU/mL, p = 0.01) and second-phase insulin (236.2 ± 40.7 vs. 105.1 ± 17.9 µU/mL, p = 0.008), and first-phase C-peptide (8.2 ± 1.2 vs. 5.0 ± 0.3 ng/mL, p = 0.02) and second-phase C-peptide (10.8 ± 0.9 vs. 7.6 ± 0.6 ng/mL, p = 0.012) were higher in AA. β-Cell function relative to IS was higher in AA vs. AW (259.5 ± 35.3 vs. 168.8 ± 25.1 mg/kg FFM/min, p = 0.043).

CONCLUSIONS

Racial differences in insulin secretion can be demonstrated with the clamp technique in obese adolescents with T2DM. Similar to non-diabetic youth, AA adolescents with T2DM compared with their AW counterparts have an upregulated β-cell function relative to IS, the reasons for which remain to be investigated.

Association between dairy product intake and abdominal obesity in Azorean adolescents

BACKGROUND

Some studies have reported an inverse association between dairy product (DP) consumption and weight or fat mass loss.

OBJECTIVES

The objective of our study was to assess the association between DP intake and abdominal obesity (AO) among Azorean adolescents.

SUBJECTS/METHODS

This study was a cross-sectional analysis. A total of 903 adolescents (370 boys) aged 15-16 years was evaluated. Anthropometric measurements were collected (weight, height and waist circumference (WC)) and McCarthy's cut-points were used to categorize WC. AO was defined when WC was ≥90th percentile. Adolescent food intake was assessed using a self-administered semiquantitative food frequency questionnaire and DP intake was categorized in <2 and ≥2 servings/day. Data were analyzed separately for girls and boys, and logistical regression was used to estimate the association between DPs and AO adjusting for potential confounders.

RESULTS

The prevalence of AO was 54.9% (boys: 32.1% and girls: 70.7%, P<0.001). For boys and girls, DP consumption was 2.3±1.9 and 2.1±1.6 servings/day (P=0.185), respectively. In both genders, the proportion of adolescents with WC <90th percentile was higher among individuals who reported a dairy intake of <2 servings/day compared with those with an intake <2 servings/day (boys: 71% vs 65% and girls: 36% vs 24%, P<0.05). After adjustments for confounders, two or more DP servings per day were a negative predictor of AO (odds ratio, 0.217; 95% confidence interval, 0.075-0.633) only in boys.

CONCLUSION

We found a protective association between DP intake and AO only in boys.

25-hydroxyvitamin D concentrations and in vivo insulin sensitivity and β-cell function relative to insulin sensitivity in black and white youth

OBJECTIVE

To examine the relationships between plasma 25-hydroxyvitamin D [25(OH)D] and in vivo insulin sensitivity and β-cell function relative to insulin sensitivity, disposition index (DI), in black and white youth.

RESEARCH DESIGN AND METHODS

Plasma 25(OH)D concentrations were analyzed in banked specimens in healthy youth aged 8 to 18 years who had existing data on hyperinsulinemic-euglycemic and hyperglycemic clamp to assess insulin sensitivity and secretion, and measurements of body composition, and abdominal visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT).

RESULTS

A total of 183 research volunteers (mean ± SD; age, 12.6 ± 2.2 years; 98 white, 98 male, 92 obese) were studied. Analysis of HbA(1c), fasting glucose and insulin, insulin sensitivity, and DI across quartiles of plasma 25(OH)D revealed no differences among whites. In blacks, the observed significance of higher insulin sensitivity and DI in the highest quartile of 25(OH)D disappeared after adjusting for any of the adiposity measures (BMI or fat mass or VAT or SAT). The difference in insulin sensitivity (9.4 ± 1.2 vs. 5.6 ± 0.5 mg/kg/min per μU/mL; P = 0.006) between 25(OH)D nondeficient (≥20 ng/mL) versus deficient (<20 ng/mL) black youth also was negated when adjusted for adiposity.

CONCLUSIONS

In healthy youth, plasma 25(OH)D concentrations bear no independent relationship to parameters of glucose homeostasis and in vivo insulin sensitivity and β-cell function relative to insulin sensitivity. It remains to be determined whether in youth with dysglycemia the relationships are different and whether vitamin D optimization enhances insulin sensitivity and β-cell function.

Metabolomic profiling of fatty acid and amino acid metabolism in youth with obesity and type 2 diabetes: evidence for enhanced mitochondrial oxidation

OBJECTIVE

We compared acylcarnitine (AcylCN) species, common amino acid and fat oxidation (FOX) byproducts, and plasma amino acids in normal weight (NW; n = 39), obese (OB; n = 64), and type 2 diabetic (n = 17) adolescents.

RESEARCH DESIGN AND METHODS

Fasting plasma was analyzed by tandem mass spectrometry, body composition by dual energy X-ray absorptiometry and computed tomography, and total-body lipolysis and substrate oxidation by [(2)H(5)]glycerol and indirect calorimetry, respectively. In vivo insulin sensitivity (IS) was assessed with a 3-h hyperinsulinemic-euglycemic clamp.

RESULTS

Long-chain AcylCNs (C18:2-CN to C14:0-CN) were similar among the three groups. Medium- to short-chain AcylCNs (except C8 and C10) were significantly lower in type 2 diabetes compared with NW, and when compared with OB, C2-, C6-, and C10-CN were lower. Amino acid concentrations were lower in type 2 diabetes compared with NW. Fasting lipolysis and FOX were higher in OB and type 2 diabetes compared with NW, and the negative association of FOX to C10:1 disappeared after controlling for adiposity, Tanner stage, and sex. IS was lower in OB and type 2 diabetes with positive associations between IS and arginine, histidine, and serine after adjusting for adiposity, Tanner stage, and sex.

CONCLUSIONS

These metabolomics results, together with the increased rates of in vivo FOX, are not supportive of defective fatty acid or amino acid metabolism in obesity and type 2 diabetes in youth. Such observations are consistent with early adaptive metabolic plasticity in youth, which over time-with continued obesity and aging-may become dysfunctional, as observed in adults.

Four-Year Trends in Cardiometabolic Risk Factors according to Baseline Abdominal Obesity Status in West-African Adults: The Benin Study

The study examined whether abdominal obesity (AO) according to waist circumference was associated with more unfavourable changes in other cardiometabolic risk (CMR) factors in sub-Saharan Africans. The study included 541 randomly selected and apparently healthy subjects (50% women) aged 25-60 years. Complete data at baseline, 24, and 48 months later was available in 366 subjects. AO was associated with higher CMR at baseline and over the follow-up period, except for high blood pressure. A significantly higher incidence of high ratio of total cholesterol : HDL-cholesterol (TC/HDL-C) was associated with AO. Controlling for WC changes, age, baseline diet, and lifestyles, the relative risk (RR) of low HDL-C and high TC/HDL-C was 3.2 (95% CI 1.06-9.61) and 7.4 (95% CI 2.01-25.79), respectively, in AO men; the RR was not significant in women. Over a four-year period, AO therefore appeared associated with an adverse evolution of cholesterolemia in the study population.

Genetic influences in childhood obesity: recent progress and recommendations for experimental designs

The increasing prevalence of pediatric obesity around the world has become an area of scientific interest because of public health concern. Although since early stages of the lifespan body weight might be heavily influenced by an individual's behavior, epidemiological research highlights the involvement of genetic influences contributing to variation in fat accumulation and thus body composition. Results from genome-wide association studies and candidate gene approaches have identified specific regions across the human genome influencing obesity-related phenotypes. Reviewing the scientific literature provides support to the belief that at the conceptual level scientists understand that genes and environments do not act independently, but rather synergistically, and that such interaction might be the responsible factor for differences within and among populations. However, there is still limited understanding of genetic and environmental factors influencing fat accumulation and deposition among different populations, which highlights the need for innovative experimental designs, improved body composition measures and appropriate statistical methodology.

Cross-sectional association between blood pressure, in vivo insulin sensitivity and adiponectin in overweight adolescents

AIMS

To examine the cross-sectional relationship between blood pressure (BP) and (1) in vivo insulin sensitivity (IS) and (2) circulating adiponectin levels in overweight adolescents, and to determine if these relationships are driven by adiposity.

METHODS

Sixty-five white pubertal overweight adolescents underwent a hyperinsulinemic-euglycemic clamp to measure IS. Body composition and abdominal adiposity were determined by dual energy X-ray absorptiometry and computed tomography scan. BP was measured by an automated sphygmomanometer every 10 min over 1 h, between 06:00 and 07:00 a.m.

RESULTS

In vivo IS was not associated with BP after adjustment for adiposity measurements (body mass index, percentage body fat or abdominal adiposity). However, adiponectin was inversely related to systolic BP independent of adiposity.

CONCLUSION

Our findings demonstrate that in overweight adolescents the relationship between in vivo IS and systolic BP is mediated through adiposity. However, the association between adiponectin and BP is independent of adiposity suggestive of a potential modulatory role of adiponectin in BP regulation.

Validation of ultrasound estimates of visceral fat in black South African adolescents

Accurate quantification of visceral adipose tissue (VAT) is needed to understand ethnic variations and their implications for metabolic disease risk. The use of reference methods such as computed tomography (CT) and magnetic resonance imaging (MRI) is limited in large epidemiological studies. Surrogate measures such as anthropometry and dual-energy X-ray absorptiometry (DXA) do not differentiate between VAT and subcutaneous abdominal adipose tissue (SCAT). Ultrasound provides a validated estimate of VAT and SCAT in white populations. This study aimed to validate the use of ultrasound-based assessment of VAT in black South African adolescents. One hundred healthy adolescents (boys = 48, girls = 52) aged 18-19 years participating in the birth to twenty cohort study had VAT and SCAT measured by single slice MRI at L4. These MRI "criterion measures" were related to ultrasound VAT and SCAT thickness, anthropometry (BMI, waist and hip circumferences), and DXA android region fat. Ultrasound VAT thickness showed the strongest correlations with MRI VAT (Spearman's correlation coefficients: r = 0.72 and r = 0.64; in boys and girls, respectively), and substantially improved the estimation of MRI VAT compared to anthropometry and DXA alone; in regression models the addition of ultrasound VAT thickness to models containing BMI, waist, and DXA android fat improved the explained variance in VAT from 39% to 60% in boys, and from 31% to 52% in girls. In conclusion, ultrasound substantially increased the precision of estimating VAT beyond anthropometry and DXA alone. Black South African adolescents have relatively little VAT compared to elderly whites, and we therefore provide new ultrasound-based prediction equations for VAT specific to this group.