Adiposity measures as indicators of metabolic risk factors in adolescents

Obesity anthropometric indicators associated with cardiometabolic risk in Portuguese children and adolescents

The purpose of this study was to determine the association between cardiometabolic risk with body mass index and skinfold independently or in combination in youth. This cross-sectional study comprised a convenience sample of 450 children and adolescents (255 girls), aged 10 to 18 years old. Indicators of body composition were measured, and hemodynamic assessment completed. The association between body mass index and/or sum of skinfolds and cardiometabolic risk (z score of the sum of triglycerides/high density lipoprotein cholesterol, waist circumference, and mean blood pressure), was calculated using Generalized Linear Models Regression. The results showed that youngsters classified as overweight or obese with the highest skinfold measurements had the strongest association with cardiometabolic risk (< beta >: 2.60; IC 95%: 2.25–3.0) when compared with those exhibiting normal skinfold thickness (< beta >: 1.78; IC 95%: 1.30–2.20). Body mass index was most strongly associated with cardiometabolic risk (< beta >: 1.78; IC 95%: 1.3–2.2), in comparison to skinfold thickness, which was associated to a lesser extent (< beta >: 0.41; IC 95%: 0.34–0.49). Results of this cross-sectional study indicate that body mass index is more strongly associated with cardiometabolic risk than skinfold thickness. However when these two measures of overweight/obesity are combined, prediction of cardiometabolic risk is further improved. It is therefore important that public health professionals consider both body mass index and sum of skinfolds to better predict cardiometabolic risk in overweight and obese youth. Implications for future research include the use of longitudinal designs and inclusion of children from other racial/ethnic groups.

•

Body mass index and skinfold improved the prediction of cardiometabolic risk.

•

Body mass index seems to be the best indicator of cardiometabolic risk factors.

•

Anthropometric indicators are cost-effective screening of overweight/obesity.

A randomized controlled trial on a multicomponent intervention for overweight school-aged children - Copenhagen, Denmark

Background

Obesity amongst children is a growing problem worldwide. In contrast to adults, little is known on the effects of controlled weight loss on components of the metabolic syndrome in children. The primary aim of the study was to evaluate the effects of a 20-week exercise and diet guidance intervention on body mass index (BMI) in a group of overweight children. Our hypothesis was an observed reduction in BMI and secondarily in body fat content, insulin insensitivity, and other components of the metabolic syndrome in the intervention group.

Methods

School children from Copenhagen were randomly allocated to an intervention group (n = 19) or a control group (n = 19). Anthropometric assessment, whole body dual-energy X-ray absorptiometry scan, two hours oral glucose tolerance test, steps measured by pedometer, and fitness tests were measured at baseline and at 20 weeks.

Results

Thirty-seven children (30 girls) participated at baseline, aged 8.7 ± 0.9 years with a BMI of 21.8 ± 3.7 kg/m² (mean ± SD), and 36 children completed the study. The intervention group decreased their BMI (the intervention effect is the difference in change between the groups adjusted for the respective baseline values (DELTA) = -2.0 kg/m², 95% CI: -2.5; -1.5, P <0.001), total body mass (DELTA = -4.0 kg, 95% CI: -4.9; -3.0, P <0.001), and fat mass (DELTA = -3.3 kg, 95% CI: -4.2; -2.7, P <0.001) compared to the control group after the intervention. The intervention group displayed decreased waist, hip and waist-to-height ratio (WHtR) (all three variables; P <0.001), area under curve for plasma insulin (P <0.05), and increased mean and minimum steps/day (P <0.05 and P <0.01, respectively).

Conclusions

The multicomponent intervention had significant favorable effects on BMI, weight, WHtR, mean and minimum steps/day, and fat mass. In addition, similar beneficial metabolic effects were found in the children as shown in adults, e.g. increase in peripheral insulin sensitivity.

Trial registration

Clinicaltrials.gov Identifier number NCT01660789.

Validation of a BMI cut-off point to predict an adverse cardiometabolic profile with adiposity measurements by dual-energy X-ray absorptiometry in Guatemalan children

OBJECTIVE

To identify a body fat percentage (%BF) threshold related to an adverse cardiometabolic profile and its surrogate BMI cut-off point.

DESIGN

Cross-sectional study.

SETTING

Two public schools in poor urban areas on the outskirts of Guatemala City.

SUBJECTS

A convenience sample of ninety-three healthy, prepubertal, Ladino children (aged 7-12 years).

RESULTS

Spearman correlations of cardiometabolic parameters were higher with %BF than with BMI-for-age Z-score. BMI-for-age Z-score and %BF were highly correlated (r=0·84). The %BF threshold that maximized sensitivity and specificity for predicting an adverse cardiometabolic profile (elevated homeostasis model assessment-insulin resistance index and/or total cholesterol:HDL-cholesterol ratio) according to receiver operating characteristic curve analysis was 36 %. The BMI-for-age Z-score cut-off point that maximized the prediction of BF ≥ 36 % by the same procedure was 1·5. The area under the curve (AUC) for %BF and for BMI data showed excellent accuracy to predict an adverse cardiometabolic profile (AUC 0·93 (sd 0·04)) and excess adiposity (AUC 0·95 (sd 0·02)).

CONCLUSIONS

Since BMI standards have limitations in screening for adiposity, specific cut-off points based on ethnic-/sex- and age-specific %BF thresholds are needed to better predict an adverse cardiometabolic profile.

[Accuracy of body fat and waist circumference in predicting metabolic abnormalities indicating cardiovascular risk in adolescents]

OBJECTIVE

To evaluate the performance of percent body fat (%BF) and waist circumference (WC) in predicting metabolic abnormalities indicating cardiovascular risk in adolescents.

SUBJECTS AND METHODS

Cross-sectional study with a probabilistic sample of 573 adolescents aged 12 to 19 years from state public schools in Niterói, RJ. The Receiver Operating Characteristic Curve was used to evaluate the accuracy of WC and %BF in predicting alterations in blood pressure, lipid profile, and blood glucose.

RESULTS

The best %BF cutoff points were 21% for boys, and 23% for girls, with sensitivity (SE) and specificity (SP) of approximately 60%. The best WC cutoff points were 71 cm for boys, and 66 cm for girls (SE: 55% to 70%; SP: 55% to 78%).

CONCLUSION

Even the best cutoff points misidentified high proportions of adolescents with metabolic abnormalities. Caution is recommended in the use of these indicators for cardiovascular risk screening in this age group.

BMI percentiles for the identification of abdominal obesity and metabolic risk in children and adolescents: evidence in support of the CDC 95th percentile

OBJECTIVES

Body mass index (BMI) percentiles have been routinely and historically used to identify elevated adiposity. The aim of this study was to investigate the optimal Centers for Disease Control and Prevention (CDC) BMI percentile that predicts elevated visceral adipose tissue (VAT), fat mass and cardiometabolic risk in a biracial sample of children and adolescents.

PARTICIPANTS AND METHODS

This cross-sectional analysis included 369 white and African-American children (5-18 years). BMI was calculated using height and weight and converted to BMI percentiles based on CDC growth charts. Receiver operating characteristic curve analysis identified the optimal (balance of sensitivity and specificity) BMI percentile to predict the upper quartile of age-adjusted VAT (measured by magnetic resonance imaging), age-adjusted fat mass (measured by dual-energy X-ray absorptiometry) and elevated cardiometabolic risk (≥ 2 of high glucose, triglycerides and blood pressure, and low high-density lipoprotein cholesterol) for each race-by-sex group.

RESULTS

The optimal CDC BMI percentile to predict those in the top quartile of age-adjusted VAT, age-adjusted fat mass and elevated cardiometabolic risk were the 96th, the 96th and the 94th percentiles, respectively, for the sample as a whole. Sensitivity and specificity was satisfactory (>0.70) for VAT and fat mass. Compared to VAT and fat mass, there was a lower overall accuracy of the optimal percentile in identifying those with elevated cardiometabolic risk.

CONCLUSIONS

The present findings support the utility of the 95th CDC BMI percentile as a useful threshold for the prediction of elevated levels of VAT, fat mass and cardiometabolic risk in children and adolescents.

Changes in lipidemia during chronic care treatment of childhood obesity

BACKGROUND

Childhood obesity and related co-morbidities are increasing. This intervention study assessed the associations between weight changes and lipidemia in obese children and adolescents.

METHODS

A total of 240 obese children and adolescents (median age, 11.3 years; range, 3.9-20.9) were enrolled in a best-practice multidisciplinary chronic care treatment program. The concentrations of total cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), and triglycerides (TGs) and anthropometric data comprising height and weight were collected at baseline and after up to 39 months of continuous treatment.

RESULTS

The BMI standard deviation score (SDS) decreased in 51% of patients and maintained unchanged in 32% of patients during the treatment. At baseline, 65 (27.1%) of the patients exhibited dyslipidemia defined as increased concentrations of total cholesterol (>200 mg/dL), LDL (>130 mg/dL), or TGs (>150 mg/dL), or decreased HDL concentration (<35 mg/dL). Dyslipidemia improved with weight loss; the odds ratio (OR) was 0.37 per BMI SDS (p = 0.014) after adjusting for age, sex, and baseline BMI SDS. Baseline TG concentration correlated positively and HDL concentration correlated negatively with baseline BMI SDS. Weight loss was associated with a decrease in the concentrations of total cholesterol (p = 0.0005), LDL (p < 0.0001), non-HDL (p < 0.0001), and TGs (p < 0.0001), and with an increase in HDL concentration (p < 0.0001).

CONCLUSION

High lipid concentrations were associated with childhood obesity. The lipid profile improved during weight loss independently of the baseline BMI SDS and baseline lipid concentration.

Obesity is associated with insulin resistance and components of the metabolic syndrome in Lebanese adolescents

Background

Prevalence of metabolic syndrome (MS) in obese adolescents has been reported to range between 18–42%, depending on country of origin, thus suggesting an ethnic-based association between obesity and MS.

Aim

This study aims to investigate the magnitude of the association between obesity, insulin resistance and components of MS among adolescents in Lebanon.

Subjects and methods

The sample included 263 adolescents at 4^th and 5^th Tanner stages of puberty (104 obese; 78 overweight; 81 normal weight). Anthropometric, biochemical and blood pressure measurements were performed. Body fat was assessed using dual-energy X-ray absorptiometry.

Results

According to International Diabetes Federation criteria, MS was identified in 21.2% of obese, 3.8% of overweight and 1.2% of normal weight subjects. The most common metabolic abnormalities among subjects having MS were elevated waist circumference (96.2%), low HDL (96.2%) and hypertriglyceridemia (73.1%). Insulin resistance was identified in all subjects having MS. Regression analyses showed that percentage body fat, waist circumference and BMI were similar in their ability to predict the MS in this age group.

Conclusions

MS was identified in a substantial proportion of Lebanese obese adolescents, thus highlighting the importance of early screening for obesity-associated metabolic abnormalities and of developing successful multi-component interventions addressing adolescent obesity.

Ability of different adiposity indicators to identify children with elevated blood pressure

OBJECTIVE

Body composition measured by dual-energy X-ray absorptiometry (DXA) is believed to be superior to crude measures such as BMI or waist circumference (WC) to assess health risks associated with adiposity in adults. We compared the ability of BMI, WC, waist-to-height ratio (WHtR), percentage body fat from skinfold thickness, and measures of total and central fat assessed by DXA to identify children with elevated blood pressure (BP).

STUDY DESIGN

The QUALITY Study follows 630 Caucasian families (father, mother, and child originally aged 8-10 years). BP, height, weight, WC, and skinfold thickness were measured according to standardized protocols. Elevated BP was defined as systolic or diastolic BP at least 90th age, sex, and height-specific percentile. Total and central fat were determined with DXA. The area under the receiver operating characteristic (ROC) curve (AUC) statistic was computed from logistic models that adjusted for age, sex, height, Tanner stage, and physical activity.

RESULTS

All adiposity indicators were highly correlated. WC and WHtR did not show superior ability over BMI to identify children with elevated SBP (P = 0.421 and 0.473). Measures of total and central fat from DXA did not show an improved ability over BMI or WC to identify children with elevated SBP (P = 0.325-0.662).

CONCLUSION

Results support the use of BMI in clinical and public health settings, at least in this age group. As all indicators had a limited ability to identify children with elevated BP, results also support measurement of BP in all children of this age independent of a weight status.

The identification of children with adverse risk factor levels by body mass index cutoffs from 2 classification systems: the Bogalusa Heart Study

BACKGROUND

The cutoffs from the Centers for Disease Control and Prevention (CDC) growth charts and from the Cooper Institute (FitnessGram) are widely used to identify children who have a high body mass index (BMI).

OBJECTIVE

We compared the abilities of these 2 systems to identify children who have adverse lipid concentrations and blood pressure measurements and the reliability (consistency) of each classification system over time (mean follow-up: 7 y).

DESIGN

A cross-sectional analysis based on data from 22,896 examinations of 5- to 17-y-olds was conducted. Principal components analyses were used to summarize levels of the 5 risk factors, and likelihood ratios and the κ statistic were used to compare the screening abilities of the 2 systems. Of these children, 3972 were included in longitudinal analyses.

RESULTS

There were marked differences in the prevalence of a high FitnessGram BMI by age, with the prevalence among boys increasing from 2.5% to 21% between the ages of 5 and 11 y. The identification of adverse risk factors by the 2 systems was only fair (κ = 0.25), but there was little difference in the abilities of the CDC and FitnessGram cutoffs to identify high-risk children. Longitudinal analyses, however, indicated that the agreement between initial and follow-up FitnessGram classifications was substantially lower than that based on CDC cutoffs (κ = 0.28 compared with 0.49).

CONCLUSIONS

The FitnessGram and CDC cutoffs have similar abilities to identify high-risk children. However, a high FitnessGram BMI is difficult to interpret because the reliability over time is low, and the prevalence increases markedly with age.

Body fat reference curves for healthy Turkish children and adolescents

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

CONCLUSIONS

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