Evaluation of BMI-based classification of adolescent overweight and obesity: choice of percentage body fat cutoffs exerts a large influence. The COMPASS study

The apple doesn't fall far from the tree: is there a connection between the body mass indexes of adolescents and their parents?

OBJECTIVES

Adolescent cases suffering from obesity tend to increase in middle-income countries. This study focused on the relationship between adolescent obesity and parents body mass index (BMI) and the variables of satisfaction, diet implementation and sports promotion.

METHODS

This cross-sectional study was conducted among adolescents living in the Mediterranean region (n=522, evaluated n=488). Anthropometric measurements were taken by expert researchers and data were collected using face-to-face survey technique.

RESULTS

The average BMI of the adolescents and parents' was found to be above normal values. In adolescents, there was a positive and very good correlation with maternal BMI (r=0.711, p<0.01), a positive and moderate correlation with paternal BMI (r=0.512, p<0.01); In girl adolescents, it was positively and very well with maternal BMI (r=0.731, p<0.01), positively and moderately with father BMI (r=0.549, p<0.01); In boy adolescents, a positive and good correlation was found with maternal BMI (r=0.698, p<0.01), and a positive and moderate correlation with paternal BMI (r=0.459, p<0.01). In the analyzes comparing those who thought obesity threatened them (group 1) and those who did not think it threatened them (group 2), there was a statistically significant difference between the groups in terms of BMI distribution, satisfaction with body weight, diet program implementation, diet recommendation by the family and sports encouragement (p<0, 05).

CONCLUSIONS

In a cross-sectional perspective paternal obesity is also significant in adolescents and the correlation with maternal obesity is relatively more effective. Also includes evidence of individual efforts and parental contribution in adolescents who see obesity as a threat.

The triponderal mass index as a measure of adiposity in pediatric survivors of acute lymphoblastic leukemia: a cross-sectional study

Acute lymphoblastic leukemia (ALL) is the most common type of childhood cancer. Treatments of ALL predispose survivors to obesity, which increases the risk of cardiovascular disease and diabetes. The hallmark of obesity is excess fat mass, and adiposity is a superior predictor of cardiometabolic risk when compared to Body Mass Index (BMI), yet clinical measures of adiposity in children are lacking. The Tri-Ponderal Mass Index (TMI) (kg/m³) is a more accurate adiposity measure compared to BMI z-score in the general pediatric population. This cross-sectional study aimed to validate TMI as an adiposity measure against DEXA scan-derived adiposity, and to compare it to BMI z-score, in pediatric ALL survivors. This study was a retrospective chart review of pediatric ALL survivors diagnosed between 2004 and 2015 at McMaster Children’s Hospital, a tertiary pediatric center in Ontario, Canada. One hundred and thirteen patients (Female n = 55, 48.70%) were included, and adiposity was measured using DEXA scans. Exploratory partial correlations and linear regression analyses were adjusted for age, sex, ethnicity, and ALL risk status. Both TMI and BMI z-score correlated with the DEXA-measured fat mass percentage (FM%) (partial correlation TMI versus FM% r = 0.56; p value < 0.0001; BMI z-score versus FM% r = 0.55; p value < 0.0001). In regression analyses, the association of TMI was not inferior to BMI z-score in assessing adiposity (TMI versus FM% estimated unstandardized B 0.80, 95% CI 0.56, 1.02; p value < 0.0001; BMI z-score versus FM% (unstandardized B 0.37, 95% CI 0.26, 0.49; p value < 0.0001). The TMI is a useful clinical adiposity-specific measure in survivors of pediatric ALL.

The Tri-ponderal Mass Index is associated with adiposity in adolescent type 2 diabetes mellitus: a cross-sectional analysis

Pediatric type 2 diabetes mellitus (T2DM) patients are often overweight or obese, yet there are no validated clinical measures of adiposity to stratify cardiometabolic risk in this population. The tri-ponderal mass index (TMI, kg/m³) has recently been reported as a measure of adiposity in children, but there has been no validation of the association of TMI with adiposity in pediatric T2DM. We hypothesized that in children with T2DM, the TMI can serve as a more accurate measure of adiposity when compared to BMI z-score, and that it is associated with components of the metabolic syndrome. This is a cross-sectional secondary data analysis from the Improving Renal Complications in Adolescents with Type 2 Diabetes Through REsearch (iCARE) study (n = 116, age 10.20–17.90 years). Spearman’s correlations and multivariable regression were used in the analyses. When compared to DXA, TMI demonstrated significant correlation with total adiposity versus BMI z-score (TMI r = 0.74, p-value < 0.0001; BMI z-score r = − 0.08, p-value 0.403). In regression analyses, TMI was associated with WHtR (B = 35.54, 95% CI 28.81, 42.27, p-value < 0.0001), MAP dipping (B = 1.73, 95% CI 0.12, 3.33, p-value = 0.035), and HDL (B = − 5.83, 95% CI − 10.13, − 1.54, p-value = 0.008). In conclusion, TMI is associated with adiposity and components of the metabolic syndrome in pediatric T2DM patients.

ANTHROPOMETRIC MEASUREMENTS, DIETARY HABITS, SERUM LIPID AND GLUCOSE LEVELS IN RELATION TO HIGH BLOOD PRESSURE AMONG ADOLESCENT BOYS AND GIRLS IN CROATIA

The aim was to determine differences in anthropometric measurements, dietary habits, serum lipid and glucose levels in relation to high blood pressure (BP) among adolescent boys and girls in Croatia. The specific aim was to determine the effect of dietary habits and lifestyle on high BP in adolescents according to sex. The study included 260 (68.2%) adolescent girls and 121 (31.8%) boys with anthropometric data obtained (without missing values) from 246 girls and 111 boys. Participants answered questions from the questionnaire and anthropometric BP and blood test values were obtained. Non-parametric tests were used in analyses of reference intervals of systolic and diastolic BP in adolescent boys and girls according to age. High BP was defined as ≥90^th percentile for adolescent girls and boys, with a value of ≥135/87.5 mm Hg. Mann-Whitney U test was used to analyze differences in anthropometric and laboratory values between the groups of girls and boys with high (≤90^th percentile) and normal BP. Increase in systolic and diastolic BP was noted in the adolescents. In girls, BP values showed a decreasing systolic and increasing diastolic BP trend with age. Girls with high BP had a significantly higher body mass index (BMI) (p=0.020), waist circumference (WC) (p=0.002), waist-to-height ratio (WHtR) (p=0.016), waist-to-hip ratio (WHR) (p=0.043), hip circumference (HC) (p=0.015), triglyceride (TG) levels (p=0.021), higher prevalence of unhealthy diet at school breakfast (p=0.008) and lower prevalence of eating fish (p=0.02). Boys with high BP had a significantly higher BMI (p=0.045), WC (p=0.004), WHtR (p=0.017), WHR (p=0.022) and higher prevalence of eating meat products (p=0.015). Effective health interventions are needed to reduce the risk of developing cardiovascular diseases and preventing age-related illness.

Youth Preferences for Weight-Related Conversations

Little guidance is available to clinicians on how to talk about weight with their patients. The aim of this study is to explore youth preferences for weight-related conversations. Participants came from the National MyVoice Text Message Cohort. Between 7/2017 and 01/2018, 952 MyVoice participants provided open-ended responses via text message to three questions about weight-related conversations ("Has your doctor ever talked to you about weight?", "What did he or she say?", and "What should a doctor NOT say when talking about weight?"). The presence of themes was coded using standard qualitative methods. Of the 952 respondents, 568 (60%) reported that their doctor had talked with them about weight. Of these, 85% indicated that their doctor had notified them of their weight, BMI, or weight status and/or the need to change their body weight and 16% had doctors who provided advice about weight control. Eight themes emerged from the analysis of responses to the question "What should a doctor NOT say when talking about weight?". The two most common themes were: (1): Avoid stigmatizing terms/language (32%); and (2) Do not shame patient for their weight (25%). Findings suggest that weight-related conversations do not reflect the preferences of the youth they are designed to benefit. Youth recommended that clinicians focus on health and sustainable behavioral solutions, avoid stigmatizing language and comparing them to others, and be aware of the potential harm associated with making assumptions that conflate weight with health behaviors, morality, or appearance.

Diagnostic performance of body mass index in detection of obesity using different cutoff points for excess body fat

OBJECTIVES

The aim of this study was to assess the diagnostic sensitivity of body mass index (BMI) in detecting obesity according to different cutoff points in order to classify a high body fat percentage (%BF) in adolescents and young adults.

METHODS

This was a cross-sectional study conducted with 2447 adolescents 18 and 19 y of age residing in São Luís, Brazil and 951 young adults 21 to 23 y of age residing in Ribeirão Preto, Brazil. Three references were used to define a high %BF (i.e., those of Williams et al., Ramírez-Vélez et al., and Macias et al.). The area under the receiver operating characteristic area under the curve (AUC) was used to assess the performance of BMI.

RESULTS

Sensitivity ranged from 38.3% to 54.1% among boys and from 12.7% to 72.7% among girls. Among young adults, it ranged from 52.3% to 67.1% in men and from 33.7% to 86.6% in women. The AUC ranged from 0.69 to 0.76 among boys, from 0.56 from 0.85 among girls, from 0.75 to 0.80 among men, and from 0.67 to 0.88 among women. The best cutoff points for the BMI were 24.79 to 25.10 kg/m² for boys, 21.89 to 27.04 kg/m² for girls, 26.43 to 28.22 kg/m² for men, and 23.34 to 29.28 kg/m² for women.

CONCLUSION

The use of different references for the classification of a high %BF implied a difference in the diagnostic sensitivity of the BMI. Higher cutoff points resulted in greater sensitivity and ability to differentiate individuals with and without obesity.

Dietary Polyphenol Intake Associated with Adiposity Indices among Adults from Low to Medium Socioeconomic Status in a Suburban Area of Kuala Lumpur: A Preliminary Findings

Background

Researches on polyphenols have been the interest of few parties due to its possible roles in the prevention of obesity. However, studies regarding this topic are still limited. Therefore, this study was conducted to examine the relationship between the intake of polyphenols with adiposity indices among middle-aged adults.

Methods

This cross-sectional study involved 227 adults aged 40 to 59 years at low-cost housing flats in suburban area of Cheras, Kuala Lumpur. Data collection involved food frequency questionnaire (FFQ) for polyphenols and international physical activity questionnaire (IPAQ). Subjects were measured for anthropometric parameters including height, weight, waist and neck circumferences (NC), and body fat percentage. The polyphenol intake from the diet was estimated using local polyphenol database built according to PHENOL-EXPLORER.

Results

The average intake of polyphenol of subjects was 1815 (672) mg/day. The main food sources of polyphenol were coffee with milk, followed by chocolate milk and red beans. A higher polyphenol intake according to quartile was significantly associated with a lower neck circumference (χ² = 8.30, P = 0.040), waist circumference (χ² = 8.45, P = 0.038) and body fat percentage (χ² = 8.06, P = 0.045). Binomial logistic regression analysis showed that the association remained significant for the neck circumference (P = 0.032), after controlling for age, household income, energy intake and physical activity level. More subjects with normal NC had higher intake of polyphenols (50th percentile and above). In contrast, subjects with high NC showed lower percentiles of polyphenols intake (50th percentile and below).

Conclusion

The result showed that polyphenol intake was associated with neck circumference and thus it can be suggested that polyphenol intake is associated with obesity.

The Accuracy of Body Mass Index and Gallagher's Classification in Detecting Obesity among Iranians

BACKGROUND

The study was conducted to examine the comparability of the BMI and Gallagher's classification in diagnosing obesity based on the cutoff points of the gold standards and to estimate suitable cutoff points for detecting obesity among Iranians.

METHODS

The cross-sectional study was comparative in nature. The sample consisted of 20,163 adults. The bioelectrical impedance analysis (BIA) was used to measure the variables of interest. Sensitivity, specificity, positive predictive power (PPV), and negative predictive power (NPV) were used to evaluate the comparability of the two classification methods in detecting obesity.

RESULTS

The BMI wrongly classified 29% of the obese persons as overweight. In both classifications, as age increased, the accuracy of detecting obesity decreased. The Gallagher's classification is better than MBI in detecting obesity in men with the exception of those older than 59 years. In females, the BMI was better in determining sensitivity. In both classifications, either female or male, an increase in age was associated with a decrease in sensitivity and NPV with the exception of the BMI for the 18 year olds. Gallagher can correctly classify males and females who are less than 40 and 19 years old, respectively.

CONCLUSION

Gallagher's classification is recommended for non-obese in both sexes and in obese males younger than 40 years old. The BMI is recommended for obese females. The suitable cutoff points for the BMI to detect obesity are 27.70 kg/m(2) for females and males, 27.70 kg/m(2) for females, and 27.30 kg/m(2) for males.

Relationship Between Abdominal Adiposity and Exercise Tolerance in Children With Obesity

PURPOSE

To determine whether abdominal obesity is associated with lower exercise tolerance in children.

METHODS

Waist-to-height ratios (WHtRs) were determined for 50 children aged 8 to 12 years with body mass index greater than the 95th percentile and 6-minute walk distance (6MWD) conducted.

RESULTS

Mean 6MWD was found to be 510 (standard deviation = 60) m. Univariate analysis revealed that WHtR was the only significant predictor of 6MWD (P = .01). In modeling using multiple regression analysis, 26% of the variance in 6MWD could be attributed to the participant's age, WHtR, and sex; WHtR was the only significant contributor to 6MWD (P = .001).

CONCLUSION

WHtR was the most strongly correlated factor with distance achieved on the 6-minute walk test, a measure of exercise tolerance, and is an important measure to screen for cardiovascular disease risk and to prompt further evaluation of functional exercise capacity.

Prevalence of obesity and central obesity among adolescent girls in a district school in Bangladesh

INTRODUCTION

The prevalence of childhood obesity has increased over the last two decades. Obesity is a major risk factor for chronic diseases and plays a central role in insulin resistance or metabolic syndrome.

METHODS

The aim of the study was to assess the prevalence of obesity and abdominal obesity by means of body mass index (BMI) and waist-to-height ratio (WHtR) in adolescent girls in a district school in Bangladesh. Based on age and sex specific BMI percentiles, the students were classified as normal weight (5(th)-<85(th) percentile), overweight (85(th)-<95(th) percentiles), and obese (≥95(th) percentile). Central obesity was categorized as WHtR ≥ 0.5. Adolescent girls (aged 9-17 years) attending the sixth to twelfth grades (n = 501) in a Bengali medium school participated in the study.

RESULTS

The prevalence of obesity and overweight were 23% and 14% among the girls. The prevalence of central obesity was 26%. Around 14% of girls in the normal weight group were centrally obese. There was a significant relationship between WHtR and BMI status (P = 0.0001).

CONCLUSION

Our study provides evidence showing a high prevalence of overall and central obesity in adolescent girls in our population. We emphasize the need for further large scale surveillance programs and preventive strategies in our population to reduce the incidence of obesity.

Diagnostic performance of body mass index to identify obesity as defined by body adiposity in children and adolescents: a systematic review and meta-analysis

BACKGROUND

The ideal means of identifying obesity in children and adolescents has not been determined although body mass index (BMI) is the most widely used screening tool.

OBJECTIVE

We performed a systematic review and meta-analysis of studies assessing the diagnostic performance of BMI to detect adiposity in children up to 18 years.

METHODS

Data sources were EMBASE, MEDLINE, Cochrane, Database of Systematic Reviews Cochrane CENTRAL, Web of Science and SCOPUS up to March 2013. Studies providing measures of diagnostic performance of BMI and using body composition technique for body fat percentage measurement were included.

RESULTS

Thirty-seven eligible studies that evaluated 53 521 patients, with mean age ranging from 4 to 18 years were included in the meta-analysis. Commonly used BMI cut-offs for obesity showed pooled sensitivity to detect high adiposity of 0.73 (confidence interval [CI] 0.67-0.79), specificity of 0.93 (CI 0.88-0.96) and diagnostic odds ratio of 36.93 (CI 20.75-65.71). Males had lower sensitivity. Moderate heterogeneity was observed (I(2) = 48%) explained in meta-regression by differences across studies in race, BMI cut-off, BMI reference criteria (Center for Disease Control vs. International Obesity Task Force) and reference standard method assessing adiposity.

CONCLUSION

BMI has high specificity but low sensitivity to detect excess adiposity and fails to identify over a quarter of children with excess body fat percentage.

Temporal divergence of percent body fat and body mass index in pre-teenage children: the LOOK longitudinal study

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

The index of body mass related to stature, (body mass index, BMI, kgm(-2) ), is widely used as a proxy for percent body fat (%BF) in cross-sectional and longitudinal investigations. BMI does not distinguish between lean and fat mass and in children, the cross-sectional relationship between %BF and BMI changes with age and sex.

WHAT THIS STUDY ADDS

While BMI increases linearly with age from age 8 to 12 years in both boys and girls, %BF plateaus off between 10 and 12 years. Repeated measures in children show a systematic decrease in %BF for any given BMI from age 8 to 10 to 12 years. Because changes in BMI misrepresent changes in %BF, its use as a proxy of %BF should be avoided in longitudinal studies in this age group.

BACKGROUND

Body mass index (BMI, kgm(-2) ) is commonly used as an indicator of pediatric adiposity, but with its inability to distinguish changes in lean and fat mass, its use in longitudinal studies of children requires careful consideration.

OBJECTIVE

To investigate the suitability of BMI as a surrogate of percent body fat (%BF) in pediatric longitudinal investigations.

METHODS

In this longitudinal study, healthy Australian children (256 girls and 278 boys) were measured at ages 8.0 (standard deviation 0.3), 10.0 and 12.0 years for height, weight and percent body fat (%BF) by dual-energy X-ray absorptiometry.

RESULTS

The patterns of change in the means of %BF and BMI were different (P < 0.001). While mean BMI increased linearly from 8 to 12 years of age, %BF did not change between 10 and 12 years. Relationships between %BF and BMI in boys and girls were curvilinear and varied with age (P < 0.001) and gender (P < 0.001); any given BMI corresponding with a lower %BF as a child became older.

CONCLUSION

Considering the divergence of temporal patterns of %BF and BMI between 10 and 12 years of age, employment of BMI as a proxy for %BF in absolute or age and sex standardized forms in pediatric longitudinal investigations is problematical.

The four-compartment model of body composition in obese Chilean schoolchildren, by pubertal stage: comparison with simpler models

OBJECTIVES

We assessed the agreement of body fat and fat-free mass measured by simpler methods against the four-compartment model (4C).

METHODS

In 60 obese schoolchildren (body mass index ≥95th percentile) between the ages of 8 and 13 y who were recruited from one school in Chile, multicompartmental body composition was estimated with the use of isotopic dilution, plethysmography (BodPod), radiographic absorptiometry (DEXA), and anthropometric equations. These results were compared to those of the 4C model, which is considered the gold standard.

RESULTS

For body fat, the 4C model showed the best agreement with DEXA for boys in Tanner stages I and II (r = 0.971) and with isotopic dilution for boys in Tanner stages III and IV (r = 0.984). The best agreement in girls occurred with isotopic dilution, regardless of pubertal stage (r = 0.948 for Tanner stages I and II; r = 0.978 for Tanner stages III and IV). Both isotopic dilution and the Huang, Ellis, and Deurenberg anthropometric equations underestimated body fat in boys; by contrast, DEXA, BodPod, and the Slaughter equation overestimated body fat in boys. All of the equations underestimated body fat in girls. For fat-free mass in both boys and girls, the 4C model showed the best agreement with isotopic dilution, regardless of pubertal stage. The Huang equation showed the best agreement for boys (r = 0.730 for Tanner stages I and II; r = 0.695 for Tanner stages III and IV) and for girls in Tanner stages I and II (r = 0.884). The Ellis equation had the best agreement for girls in Tanner stages III and IV (r = 0.917).

CONCLUSIONS

For obese Chilean children of both sexes, isotopic dilution and DEXA were the two-compartment methods that had the best agreement with the gold-standard 4C model for both body fat and fat-free mass; these were followed by the Huang and Ellis anthropometric equations.

Top 10 research questions related to body composition

An understanding of body composition is crucial to understanding human health, disease, and function. Research in body composition has focused on the development of assessment methods, description of normal changes in body composition with growth and development and aging, and the changes that occur in body composition in response to challenges ranging from illness to planned interventions. Each focus is significant, and in a sense, they are interdependent, because technological advances allow more sophisticated questions to be addressed, which in turn drives the development of better methods. Significant advances have been made in each area, although perhaps surprisingly basic questions remain. For example, growth trajectories are often estimated from cross-sectional data, given the resources needed for long-term observational studies, and thus, longitudinal descriptive data are still needed. Along with advances in laboratory methods, development of field methods remains relevant for screening and clinical practice. Despite recognition of wide interindividual differences in intervention response, average outcomes continue to be emphasized. With technological advances, it is now possible to examine genetic along with nongenetic factors that underlie changes in body composition, and these techniques need to be applied in long-term, well-controlled trials. In this article, we review 10 key questions in related areas in which research is needed to continue to advance the field.

Effect of four additional physical education lessons on body composition in children aged 8-13 years--a prospective study during two school years

Background

Strategies for combating increasing childhood obesity is called for. School settings have been pointed out as potentially effective settings for prevention. The objective of this paper was to evaluate the effect of four additional Physical Education (PE) lessons/week in primary schools on body composition and weight status in children aged 8–13.

Methods

Children attending 2nd to 4th grade (n = 632) in 10 public schools, 6 intervention and 4 control schools, participated in this longitudinal study during 2 school years. Outcome measures: Primary: Body Mass Index (BMI) and Total Body Fat percentage (TBF%) derived from Dual Energy X ray Absorptiometry (DXA). Secondary: the moderating effect of overweight/obesity (OW/OB) and adiposity based on TBF% cut offs for gender.

Results

Intervention effect on BMI and TBF% (BMI: β -0.14, 95% CI: -0.33; 0.04, TBF%: β -0.08, 95% CI:-0.65;0.49) was shown insignificant. However, we found significant beneficial intervention effect on prevalence of OW/OB based on BMI (OR 0.29, 95% CI: 0.11;0.72). The intervention effect on adiposity based on TBF% cut offs was borderline significant (OR 0.64, 95% CI:0. 39; 1.05).

Conclusion

Four additional PE lessons/week at school can significantly improve the prevalence of OW/OB in primary schoolchildren. Mean BMI and TBF% improved in intervention schools, but the difference with controls was not significant. The intervention had a larger effect in children who were OW/OB or adipose at baseline.

Body fat percentile curves for Korean children and adolescents: a data from the Korea National Health and Nutrition Examination Survey 2009-2010

A valid assessment of obesity in children and adolescents is important due to significant change in body composition during growth. This study aimed to develop percentile curves of body fat and fat free mass using the Lambda, Mu, and Sigma method, and to examine the relationship among body mass index (BMI), fat mass and fat free mass in Korean children and adolescents, using the Korea National Health and Nutrition Examination Survey (KNHANES) 2009-2010. The study subjects were 834 for boys and 745 for girls aged between 10 and 18 yr. Fat mass and fat free mass were measured by dual-energy x-ray absorptiometry. The patterns of development in body fat percentage, fat mass and fat free mass differed for boys and girls, showing a decreased fat mass with an increased fat free mass in boys but gradual increases with age in girls. The considerable proportion of boys and girls with relatively normal fat mass appeared to be misclassified to be at risk of overweight based on the BMI criteria. Therefore, the information on the percentiles of body fat and fat free mass with their patterns would be helpful to complement assessment of overweight and obesity based on BMI for Korean children and adolescents.

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.

The use of Stunkard's figure rating scale to identify underweight and overweight in Chinese adolescents

BACKGROUND

To compare the performance of Stunkard's current body size (CBS) with self-reported body mass index (BMI), waist circumference (WC) and waist to stature ratio (WSR) in predicting weight status in Chinese adolescents, and to determine the CBS cutoffs for overweight/obesity and underweight.

METHODOLOGY

This cross-sectional study was conducted in a sample of 5,418 secondary school students (45.2% boys; mean age 14.7 years). Height and weight were measured by trained teachers or researchers. Subjects were classified as underweight, normal weight, or overweight/obese according to the International Obesity Task Force cutoffs. Subjects were asked to select the figure that best resembled their CBS on the Stunkard's figure rating scale. Self-reported height, weight, WC and WSR were also obtained. The performance of CBS, self-reported BMI, WC and WSR as a weight status indicator was analysed by sex-specific receiver operating characteristic curves. The optimal CBS cutoffs for underweight and overweight/obesity were determined based on the Youden Index.

PRINCIPAL FINDINGS

Apart from self-reported BMI, CBS had the greatest area under curve (AUC) for underweight in boys (0.82) and girls (0.81). For overweight/obesity, CBS also had a greater AUC (0.85) than self-reported WC and WSR in boys, and an AUC (0.81) comparable to self-reported WC and WSR in girls. In general, CBS values of 3 and 5 appeared to be the optimal cutoffs for underweight and overweight/obesity, respectively, in different sex-age subgroups.

CONCLUSIONS/SIGNIFICANCE

CBS is a potentially useful indicator to assess weight status of adolescents when measured and self-reported BMI are not available.

Can weight-related health risk be more accurately assessed by BMI, or by gender specific calculations of Percentage Body Fatness?

The problem of obesity over the last 10 years has consistently been referred to as a 'global epidemic'. The Body Mass Index (BMI) is the currently accepted measure for classifying weight-related risk, but is a crude measure that has not changed in 150 years. It is recognised as having significant limitations, largely due to its lack of distinction between fat and muscle tissue. As the health risks of obesity are linked to the fat content of the body, a more accurate method of classifying would be Percentage Body Fatness (PBF). Although skinfold thickness analysis is recognised as a valid and accurate estimate of PBF in field studies, this method is not routinely used in clinical practice. Using data collected from young adults in the United Kingdom, we compared classifications (underweight, normal weight, overweight and obese) using BMI, with classifications using estimated PBF (from skinfold thickness analysis). We identified disparity between these two methods in approximately 1/3 of participants. BMI correctly classified 66.5% of females and 62.7% of males, with different gender profiles of incorrect classification. Regression analysis was conducted using estimated PBF (by skinfold thickness analysis) as the dependent variable, with explanatory variables of age, height, weight, systolic blood pressure, frequency of vigorous exercise and grip strength. The resulting gender-specific formulae derived from this regression analysis provides a regression R(2) of around 65%, and improved correct classifications to 74% for females and 76% for males. This represents an average improvement of roughly ten percentage points over BMI (male: 7.2% points; female: 13.4% points). We hypothesise that the presented formulae provide gender-specific calculations of PBF, which result in a more accurate indicator of weight-related health risk, compared with BMI in this population. This provides a new approach to an increasingly important clinical issue. These formulae use data that can be easily, quickly and cost-effectively measured in a practice setting. If shown to be repeatable with larger and more diverse populations, the PBF formulae could provide an alternative to the BMI as the major indicator of body-composition related health risk. This would ensure resources are targeted more appropriately and efficiently.

A matter of fat: insulin resistance and oxidative stress

BACKGROUND

Obesity is linked to insulin resistance (IR), which can lead to type 2 diabetes mellitus. Oxidative stress present in early obesity may favor the progression to comorbid conditions.

OBJECTIVE

To examine the relationship between oxidative stress biomarkers and the severity of IR in a group of obese children.

METHODS

Forty obese children with a body mass index (BMI) Z-score ≥ 2 were divided into two groups using the median obtained for the homeostasis model assessment of IR (HOMA-IR). Anthropometric parameters (including body fat composition by bioelectrical impedance) and biochemical parameters were assessed. The following biomarkers of oxidative stress were measured: malondialdehyde (MDA), carbonyl groups (CG), reduced glutathione, oxidized low-density lipoprotein, and vitamin E. Comparisons were adjusted for gender and Tanner stage.

RESULTS

Children with high values of HOMA-IR were more likely to have high body fat percentage and waist circumferences. However, the BMI Z-score did not correlate to the level of IR. Children with higher values of HOMA-IR presented increased levels of markers of oxidative stress in lipids (MDA, p = 0.005) and proteins (CG, p = 0.015). Moreover, MDA increased with increasing levels of HOMA-IR (r = 0.50, p = 0.002), suggesting that lipoperoxidation increases as IR worsens. In a multivariate regression model, only HOMA-IR was predictive of MDA values, irrespective of adiposity parameters and other metabolic risk factors (r2 = 0.22, p = 0.002).

CONCLUSIONS

Oxidative stress increases in obese children according to the severity of IR, which could be linked to the development of comorbidities.

Utility of the waist-to-height ratio as an instrument to measure parental perception of body weight in children and its use in a population-based survey of children

OBJECTIVE

To investigate which anthropometric measure of overweight status, BMI or waist-to-height ratio (WHtR), is most closely associated with parents' perception of their child's overweight status.

DESIGN

The sensitivity and specificity of parental perception against child-specific BMI and WHtR definitions of overweight were tested.

SETTING

Primary schools in Queensland, Australia.

SUBJECTS

Boys and girls aged 9·00-11·99 years (n 1431).

RESULTS

Of the 138 boys and 202 girls who were classified as overweight according to BMI, only 27·5 % (boys) and 22·7 % (girls) were also perceived as overweight by their parents. Using WHtR, 206 boys and 333 girls were classified as overweight, of whom only 21·9 % and 13·8 %, respectively, were perceived as overweight. Perception of overweight was underestimated in approximately 15 % of boys and 21 % of girls when compared with BMI. Underestimation was higher when compared with WHtR: 25 % (boys) and 39 % (girls). Overweight prevalence was significantly lower according to perception than according to BMI or WHtR. Mother's education level was significantly associated with accurate perception of overweight status (P < 0·001).

CONCLUSIONS

The sensitivity of parental perception of child overweight was higher when BMI was used. However, emphasis needs to be placed on using WHtR as an actual measure of overweight because high central adiposity is associated with increased risk of CVD. The combined use of WHtR, body-shape images rather than word responses regarding perception and public health messages that educate parents and children about body shape and associated health risks may be the best combination in improving parents' perception of their child's overweight status.

Body Mass Index standards based on agreement with health-related body fat

BACKGROUND

Multiple screening tools, such as BMI and skinfold-derived percent body fat (%BF), are available to identify youth at risk of excess adiposity. However, poor classification agreement among these tools can be problematic for those interpreting test results.

PURPOSE

The purpose of this study was to investigate the validity of using BMI as an estimate of %BF in youth and to identify optimal BMI thresholds for identifying at-risk children and adolescents based on %BF.

METHODS

Percent body fat was derived from the skinfold thicknesses of children aged 5-18 years from three cross-sectional waves of the National Health and Nutrition Examination Survey (NHANES [1999-2004]; N=8269). Stature and body mass from the same data set were used to calculate BMI. Receiver operating characteristic (ROC) analysis was employed to determine the optimal BMI thresholds for detecting previously created %BF standards.

RESULTS

The optimal BMI percentile associated with the low risk %BF threshold was the 83 rd and 80th in boys and girls, respectively. The selected BMI percentiles associated with the higher risk threshold were the 92 nd and 90th in boys and girls, respectively. Overall, classification accuracy when using BMI percentiles to identify the two %BF risk groups ranged from 86.9% to 89.1%.

CONCLUSIONS

BMI and skinfold-derived %BF demonstrate reasonable agreement when used to classify adiposity status in children and adolescents.

Performance of body fat and body mass index cutoffs in elevated blood pressure screening among male children and adolescents

For percentage of body fat (%BF), there are no internationally accepted cutoffs. The primary function of body fat cutoffs should be to identify not only excessive body fatness, but also the increased risk of unhealthy outcomes, such as hypertension. The purpose of this study was to analyze the accuracy of different %BF and body mass index (BMI) cutoffs as screening measures for EBP in pediatric populations. It was a cross-sectional study with a sample of 358 male subjects from 8 to 18 years old. BP was measured by the oscilometric method, and body composition was measured by dual-energy X-ray absorptiometry (DXA). The accuracy of three reference tables used for body fat cutoffs was assessed. The three body fat reference tables were highly specific, but insensitive, for elevated BP screening. For elevated BP screening, all body fat cutoffs presented similar sensitivity (range=48.3-53.7%) and specificity (range=79.2-84.1%). The body fat cutoffs performed no better than BMI in screening of children and adolescents at risk of elevated BP (EBP). BMI seems a more attractive tool for this function, as it performed similarly and can be applied in large surveys and with lower costs.

Utility of waist-to-height ratio in assessing the status of central obesity and related cardiometabolic risk profile among normal weight and overweight/obese children: the Bogalusa Heart Study

Background

Body Mass Index (BMI) is widely used to assess the impact of obesity on cardiometabolic risk in children but it does not always relate to central obesity and varies with growth and maturation. Waist-to-Height Ratio (WHtR) is a relatively constant anthropometric index of abdominal obesity across different age, sex or racial groups. However, information is scant on the utility of WHtR in assessing the status of abdominal obesity and related cardiometabolic risk profile among normal weight and overweight/obese children, categorized according to the accepted BMI threshold values.

Methods

Cross-sectional cardiometabolic risk factor variables on 3091 black and white children (56% white, 50% male), 4-18 years of age were used. Based on the age-, race- and sex-specific percentiles of BMI, the children were classified as normal weight (5th - 85th percentiles) and overweight/obese (≥ 85th percentile). The risk profiles of each group based on the WHtR (<0.5, no central obesity versus ≥ 0.5, central obesity) were compared.

Results

9.2% of the children in the normal weight group were centrally obese (WHtR ≥0.5) and 19.8% among the overweight/obese were not (WHtR < 0.5). On multivariate analysis the normal weight centrally obese children were 1.66, 2.01, 1.47 and 2.05 times more likely to have significant adverse levels of LDL cholesterol, HDL cholesterol, triglycerides and insulin, respectively. In addition to having a higher prevalence of parental history of type 2 diabetes mellitus, the normal weight central obesity group showed a significantly higher prevalence of metabolic syndrome (p < 0.0001). In the overweight/obese group, those without central obesity were 0.53 and 0.27 times less likely to have significant adverse levels of HDL cholesterol and HOMA-IR, respectively (p < 0.05), as compared to those with central obesity. These overweight/obese children without central obesity also showed significantly lower prevalence of parental history of hypertension (p = 0.002), type 2 diabetes mellitus (p = 0.03) and metabolic syndrome (p < 0.0001).

Conclusion

WHtR not only detects central obesity and related adverse cardiometabolic risk among normal weight children, but also identifies those without such conditions among the overweight/obese children, which has implications for pediatric primary care practice.

Developing waist-to-height ratio cut-offs to define overweight and obesity in children and adolescents

OBJECTIVE

The waist-to-height ratio (WHtR) assesses abdominal adiposity and has been proposed to be of greater value in predicting obesity-related cardiovascular health risks in children than BMI. The present study aims to develop WHtR cut-offs for overweight and obesity based on the 85th and 95th percentiles for the percentage body fat (%BF) in a cohort of children and adolescents.

DESIGN

Waist circumference (WC), height, triceps and subscapular skinfolds were used to calculate WHtR and %BF. Correlations between WHtR and %BF and WHtR/mid-abdominal skinfold were made. Receiver-operating characteristic (ROC) curve analysis was used to select WHtR cut-offs to define overweight and obesity. Subjects were grouped by WHtR cut-offs, and mean values for anthropometry, blood lipids and blood pressure (BP) variables were compared.

SETTING

Australian primary and secondary schools.

SUBJECTS

A total of 2773 male (M) and female (F) subjects of the 1985 Australian Health and Fitness Survey, aged 8-16 years.

RESULTS

Correlation coefficients between WHtR and %BF were M: r = 0.73, F: r = 0.60, P < 0.01 and WHtR/mid-abdominal skinfold were M: r = 0.78, F: r = 0.65, P < 0.01. WHtR of 0.46(M) and 0.45(F) best identified subjects with > or = 85th percentile for %BF and 0.48(M) and 0.47(F) identified subjects with > or = 95th percentile for %BF. When comparing the highest WHtR group to the lowest, both sexes had significantly higher means for weight, WC, %BF, TG (male subjects only), systolic BP (female subjects only) and lower means for HDL cholesterol (P < 0.05).

CONCLUSIONS

WHtR is useful in clinical and population health as it identifies children with higher %BF at greater risk of developing weight-related CVD at an earlier age.

The validity of BMI as an indicator of body fatness and risk among children

PURPOSE OF REVIEW

Although the prevalence of childhood obesity, as assessed by BMI (kg/m(2)), has tripled over the last 3 decades, this index is a measure of excess weight rather than excess body fatness. In this review we focus on the relation of BMI to body fatness and health risks, particularly on the ability of BMI for age >or=95th Centers for Disease Control and Prevention [CDC] percentile to identify children who have excess body fatness. We also examine whether these associations differ according to race/ethnicity and whether skinfold and circumference measurements provide additional information on body fatness or health risks.

RESULTS

The accuracy of BMI varies according to the degree of body fatness. Among relatively fat children, BMI is a good indicator of excess adiposity, but differences in the BMIs of relatively thin children can be largely due to fat-free mass. Although the accuracy of BMI in identifying children with excess body fatness depends on the chosen cut points, we have found that a high BMI-for-age has a moderately high (70%-80%) sensitivity and positive predictive value, along with a high specificity (95%). Children with a high BMI are much more likely to have adverse risk factor levels and to become obese adults than are thinner children. Skinfold thicknesses and the waist circumference may be useful in identifying children with moderately elevated levels of BMI (85th to 94 th percentiles) who truly have excess body fatness or adverse risk factor levels.

CONCLUSION

A BMI for age at >or=95th percentile of the CDC reference population is a moderately sensitive and a specific indicator of excess adiposity among children.

Adiposity measures as indicators of metabolic risk factors in adolescents

AIM

To examine the relation between adiposity assessment methods (percentage body fat (%BF), BMI, and waist circumference (WC)) and individual metabolic risk factors (f-insulin, HDL cholesterol, triglycerides) and a combined measure of metabolic risk.

METHODS

Crosssectional study of 300 males (BMI 20.8 +/- 3.0 kg/m(2)) and females (BMI 21.3 +/- 2.9 kg/m(2)) 17 years of age. F-insulin and components of the metabolic syndrome defined by the International Diabetes Federation (IDF) were used as metabolic risk indicators, with samples stratified into BMI, %BF, and WC groups, respectively. Diagnostic accuracy was expressed as the area under the ROC curve (AUC).

RESULTS

In males, diagnostic accuracy for HDL and f-insulin was poor to fair for BMI (AUC 0.70, p = 0.001; 0.60, p = 0.22), WC (0.68, p = 0.003; 0.63, p = 0.11), and %BF (0.65, p = 0.009; 0.66, p = 0.04). The diagnostic accuracy for triglycerides was greater for all three measures (BMI 0.92, WC 0.95, %BF 0.87; all p < 0.001). For females, neither test performed better than chance for f-insulin and HDL, and only %BF performed better than chance for triglycerides (0.65, p = 0.08). All three measures exhibited higher accuracy for presence of > or =2 metabolic risk factors (AUCs 0.76-0.91, p < 0.001) in both sexes.

CONCLUSION

%BF was not superior to BMI and WC for detecting metabolic risk in the general adolescent population.