How well do waist circumference and body mass index reflect body composition in pre-pubertal children?

Impact of BMI on peak growth hormone responses to provocative tests and therapeutic outcome in children with growth hormone deficiency

This study investigated the relationship between peak stimulated growth hormone (GH) and body mass index (BMI), as well as the impact of BMI on therapeutic response in patients with GH deficiency (GHD). A total of 460 patients were enrolled in the study. The patients were divided into four groups as per the etiology and peak GH values: idiopathic (n = 439), organic (n = 21), complete (n = 114), and partial (n = 325) GHD groups. Subsequently, they were classified as normal, overweight, or obese based on their BMI. There was no difference in BMI between complete and partial GHD. A significant negative relationship between peak GH and BMI were found. Moreover, obese GHD children had a considerably better therapeutic response in height increase and BMI decrease during 2 years of GH treatment compared to non-obese children with GHD. There was no difference between peak GH and type of GH stimulation test (GHST), except the clonidine test, which showed a much lower peak GH in obese GHD children. In conclusion, BMI had a negative impact on peak GH response, and therapeutic outcome was more favorable in the obese group. Despite no difference in GH response by type of GHST, the degree of obesity differentially affected the results.

The role and place of bioimpedance analysis assessment of body composition of children and adolescents with different body mass

The steady rise of obesity in children and adolescents emphasizes the need for new, integrated approaches to its diagnosis and therapy. When diagnosing obesity and choosing methods for its correction, it is fundamentally important to use reliable methods of estimating the amount of adipose tissue. Using the body mass index is not always sufficient, since it does not provide complete information on quantitative content in the body weight of the patient’s body. For these purposes in clinical medicine use of bioimpedance analysis to assess the indicators, which characterize the basal metabolism, active cell mass, fat and basirova mass and total water content in the body. However, the holding of bioimpedance body composition analysis is currently limited mainly to dietetics and sports medicine, and adult patients. Quite interesting is the use of the bioimpedance method in the pediatric age group for accurate evaluation of body composition of children of various ages and body weight that will allow for dynamic control of all types of metabolism to evaluate the effectiveness of the observation and treatment of patients with overweight and obesity.

Anthropometric predictors of body fat in a large population of 9-year-old school-aged children

Objective

To develop and cross‐validate predictive models for percentage body fat (%BF) from anthropometric measurements [including BMI z‐score (zBMI) and calf circumference (CC)] excluding skinfold thickness.

Methods

A descriptive study was carried out in 3,084 pre‐pubertal children. Regression models and neural network were developed with %BF measured by Bioelectrical Impedance Analysis (BIA) as the dependent variables and age, sex and anthropometric measurements as independent predictors.

Results

All %BF grade predictive models presented a good global accuracy (≥91.3%) for obesity discrimination. Both overfat/obese and obese prediction models presented respectively good sensitivity (78.6% and 71.0%), specificity (98.0% and 99.2%) and reliability for positive or negative test results (≥82% and ≥96%). For boys, the order of parameters, by relative weight in the predictive model, was zBMI, height, waist‐circumference‐to‐height‐ratio (WHtR) squared variable (_Q), age, weight, CC_Q and hip circumference (HC)_Q (adjusted r² = 0.847 and RMSE = 2.852); for girls it was zBMI, WHtR_Q, height, age, HC_Q and CC_Q (adjusted r² = 0.872 and RMSE = 2.171).

Conclusion

%BF can be graded and predicted with relative accuracy from anthropometric measurements excluding skinfold thickness. Fitness and cross‐validation results showed that our multivariable regression model performed better in this population than did some previously published models.

Review of commonly used age-based weight estimates for paediatric drug dosing in relation to the pharmacokinetic properties of resuscitation drugs

AIM

To study which weight estimate calculation used in paediatric resuscitation results in optimal drug dosing; Advanced Paediatric and Life Support (APLS) or the UK Resuscitation Council age-based formula.

METHOD

Commonly used drugs used in paediatric resuscitation were selected and a literature search conducted for each drug's pharmacokinetic properties, concentrating on the volume of distribution (Vd). Hydrophobic drugs have a higher Vd than hydrophilic drugs as they distribute preferentially to fat mass (FM). The larger the Vd, the higher the initial dose required to achieve therapeutic plasma concentrations. Actual body weight (ABW) estimates are a good indicator of Vd for hydrophobic drugs as they correlate well with FM. Ideal body weight (IBW) estimates may be a better indicator of Vd for hydrophilic drugs, as they correlate better with lean body mass. This highlights potential variation between ABW and IBW, which may result in toxic or sub-therapeutic dosing.

RESULTS

The new APLS formulae give higher estimates of expected weight for a wider age range. This may be a more accurate reflection of ABW due to increasing prevalence of obesity in children. The UK Resuscitation Council's formula appears to result in a lower estimate of weight, which may relate more closely to IBW.

CONCLUSION

The main drugs used in paediatric resuscitation are hydrophilic, thus the APLS formulae may result in too much being given. Therefore the UK Resuscitation Council's single formula may be preferred. In addition, a single formula may minimize error in the context of a child of unknown weight requiring administration of emergency resuscitation drugs.

Waist-to-height ratio centiles by age and sex for Japanese children based on the 1978-1981 cross-sectional national survey data

OBJECTIVES

To construct waist-to-height ratio (WC/Ht) reference values and centile curves for Japanese children and to compare these references with those from other countries.

METHODS

The 1978-1981 national survey data were used for reference and the 1992-1994 national survey data were used for validation. The former included 19 233 children, and the latter included 10 446 children, aged 6 to 18 years. Waist circumferences (WC) were measured at the level of maximum waist narrowing in girls, and at the level of the top of the iliac crest in boys. Age- and sex-specific reference curves were fitted with the LMS method. Cut-off points were arbitrarily set at 85th, 90th, 95th and 97th centiles, and compared with WC/Ht 0.50.

RESULTS

The proportion of children in whom WC/Ht exceeded 0.50 was 18.7% of boys and 1.9% of girls, whereas the proportion of children exceeding 90th centile was 42.4% for boys and 17.3% for girls. The reference values decreased with age in girls but varied by age without a clear trend in boys.

CONCLUSIONS

The first reference values for WC/Ht are provided for Japanese youth based on the 1978-1981 national survey data. These curves are age- and sex-dependent, precluding the use of universal cut-off for WC/Ht of 0.50.

Evidence of an overweight/obesity transition among school-aged children and youth in Sub-Saharan Africa: a systematic review

BACKGROUND

Prevalence of childhood overweight/obesity has increased considerably in recent years. The transition to higher rates of overweight/obesity has been well documented in high income countries; however, consistent or representative data from lower income countries is scarce. It is therefore pertinent to assess if rates of overweight/obesity are also increasing in lower income countries, to inform public health efforts.

OBJECTIVE

This systematic review aimed to investigate the evidence for an overweight/obesity transition occurring in school-aged children and youth in Sub Saharan Africa.

METHODS

Studies were identified by searching the MEDLINE, Embase, Africa Index Medicus, Global Health, Geobase, and EPPI-Centre electronic databases. Studies that used subjective or objective metrics to assess body composition in apparently healthy or population-based samples of children and youth aged 5 to 17 years were included.

RESULTS

A total of 283 articles met the inclusion criteria, and of these, 68 were used for quantitative synthesis. The four regions (West, Central, East, and South) of Sub Saharan Africa were well represented, though only 11 (3.9%) studies were nationally representative. Quantitative synthesis revealed a trend towards increasing proportions of overweight/obesity over time in school-aged children in this region, as well as a persistent problem of underweight. Weighted averages of overweight/obesity and obesity for the entire time period captured were 10.6% and 2.5% respectively. Body composition measures were found to be higher in girls than boys, and higher in urban living and higher socioeconomic status children compared to rural populations or those of lower socioeconomic status.

CONCLUSIONS

This review provides evidence for an overweight/obesity transition in school-aged children in Sub Saharan Africa. The findings of this review serve to describe the region with respect to the growing concern of childhood overweight/obesity, highlight research gaps, and inform interventions.

PROSPERO REGISTRATION NUMBER

CRD42013004399.

Diagnostic accuracy of anthropometric indices in predicting excess body fat among seven to ten-year-old children

PURPOSE: To evaluate the accuracy of the body mass index (BMI), waist circumference (WC) and waist-to-height ratio (WHtR) in detecting excess body fat among schoolchildren in Florianópolis, Santa Catarina. METHODS: Cross-sectional study with 2,772 schoolchildren aged seven to ten years. Receiver Operating Characteristic (ROC) curves were used to compare the diagnostic accuracy of the BMI, the WC and the WHtR in identifying children with excess body fat (defined as values that were equal to or higher than the 90th percentile of the standardized residuals obtained from the sum of the four skinfolds thickness). Likelihood ratio estimates were used to select, for each anthropometric index, the cut-off points that presented the highest association with excess body fat. RESULTS: The BMI, WC and WHtR performed well in detecting excess body fat, indicated by areas under the ROC curve (AUC) close to 1.0, with slightly higher AUC for the BMI in comparison to the WC and the WHtR concerning both sexes. Highly sensitive and specific cut-off points were derived for the three anthropometric indices. Sensitivity ranged from 85.7 to 92.9% for the BMI, from 78.6 to 89.7% for the WC, and from 78.6 to 89.2% for the WHtR. Specificity ranged from 83.2 to 91.4%, from 75.0 to 90.7%, and from 77.4 to 88.3% for the BMI, the WC and the WHtR, respectively. CONCLUSION: BMI, WC and WHtR can be used as diagnostic tests to identify excess body fat in children from seven to ten years of age.

Creation of an adiposity index for children aged 6-8 years: the Gateshead Millennium Study

OBJECTIVE

A number of measures of childhood adiposity are in use, but all are relatively imprecise and prone to bias. We constructed an adiposity index (AI) using a number of different measures.

METHODS

Detailed body composition data on 460 of the Gateshead Millennium Study cohort at the age of 6-8 years were analysed. The AI was calculated using factor analysis on age plus thirteen measures of adiposity and/or size. Correlations between these variables, the AI, and more traditional measures of adiposity in children were investigated.

RESULTS

Based on the factor loading sizes, the first component, taken to be the AI, consisted mainly of measures of fat-mass (the skinfold measurements, fat mass score, and waist circumference). The second comprised variables measuring frame size, while the third consisted mainly of age. The AI had a high correlation with body mass index (BMI) (rho = 0.81).

CONCLUSIONS

While BMI is practical for assessing adiposity in children, the AI combines a wider range of data related to adiposity than BMI alone and appears both valid and valuable as a research tool for studies of childhood adiposity. Further research is necessary to investigate the utility of AI for research in other samples of children and also in adults.

Abdominal obesity in German adolescents defined by waist-to-height ratio and its association to elevated blood pressure: the KiGGS study

OBJECTIVE

The aim of this study was to compare the fixed 0.5 cut-off and the age- and sex-specific 90th percentile (P90) for waist-to-height ratio (WHtR) in German adolescents with respect to the prevalence of abdominal obesity and to compare the screening ability of WHtR and BMI to identify hypertensive blood pressure (BP) values.

METHODS

Between 2003 and 2006, the German Health Interview and Examination Survey for Children and Adolescents (KiGGS) was carried out including 3,492 boys and 3,321 girls aged 11-17 years. Abdominal obesity was assessed by two WHtR cut-points (P90; 0.5). Hypertensive BP was defined as BP exceeding age-, sex- and height-specific 95th percentiles or the adult threshold for hypertension (140/90 mm Hg).

RESULTS

Agreement between the WHtR cut-offs was very good (Kappa 0.89 for boys; 0.81 for girls), and the prevalence of abdominal obesity was slightly higher using P90 (boys 12.0%; girls 11.3%) compared to 0.5 (boys 10.7%; girls 8.0%). WHtR and BMI-for-age had equivalent ability to discriminate hypertensive BP (ROC-AUC < 0.7; sensitivity of the 0.5 cut-off for detecting hypertensive BP < 30%).

CONCLUSION

The fixed 0.5 WHtR cut-off can be used in German adolescents to characterize abdominal obesity. However, WHtR is not suitable as a screening tool for hypertensive BP in adolescents.

A proposed cutoff point of waist-to-height ratio for metabolic risk in African township adolescents

OBJECTIVE

A waist:height ratio (WHtR) higher than 0.5 has been proposed as a cutoff point for abdominal obesity in both sexes and at all ages. It is unknown if this cutoff point is appropriate for previously undernourished adolescents. We assessed the cutoff value of the WHtR associated with an increased metabolic risk in 178 black South African 14- to 18-y-old adolescents (69 boys, 109 girls).

METHODS

We measured weight, height, waist circumference, fasting plasma glucose and insulin levels, serum high-sensitivity C-reactive protein, and blood pressure and calculated the WHtR and homeostasis model assessment of insulin resistance (HOMA-IR). Using receiver operating characteristics curve analyses, we assessed the WHtR with the highest sensitivity and specificity to discriminate adolescents with increased fasting plasma glucose, HOMA-IR, serum high-sensitivity C-reactive protein, and blood pressure from those with "normal" values.

RESULTS

The WHtR cutoff points derived from the receiver operating characteristics curves ranged from 0.40 to 0.41, with best diagnostic value at 0.41. A WHtR of 0.40 had 80% sensitivity and 38.5% specificity to classify adolescents with fasting blood glucose level higher than 5.6 mmol/L (area under the curve [AUC] 0.57). A WHtR of 0.41 had 64% sensitivity and 58.5% specificity for a HOMA-IR higher than 3.4 (AUC 0.66), 55% sensitivity and 55.6% specificity for a high-sensitivity C-reactive protein level higher than 1 mg/L (AUC 0.57), and 64% sensitivity and 50.2% specificity for a blood pressure higher than the age-, sex-, and height-specific 90th percentiles (AUC 0.56). Adolescents with a WHtR higher than 0.41 had an odds ratio of 2.46 (95% confidence interval 0.96-6.30) for having a HOMA-IR higher than 3.4.

CONCLUSION

The WHtR cutoff to indicate metabolic risk for black South African adolescents is 0.41, which is lower than the proposed international cutoff of 0.5. The WHtR can be used for screening adolescents with components of the metabolic syndrome in intervention programs.

Adiposity indices in the prediction of insulin resistance in prepubertal Colombian children

OBJECTIVE

To compare BMI with abdominal skinfold thickness (ASF), waist circumference and waist-to-height ratio in the prediction of insulin resistance (IR) in prepubertal Colombian children.

DESIGN

We calculated age- and sex-specific Z-scores for BMI, ASF, waist circumference, waist-to-height ratio and three other skinfold-thickness sites. Logistic regression with stepwise selection (P = 0·80 for entry and P = 0·05 for retention) was performed to identify predictors of IR and extreme IR, which were determined by age- and sex-specific Z-scores to identify the ≥ 90th and ≥ 95th percentile of homeostasis model assessment (HOMAIR), respectively. We used receiver operating characteristic curves to compare the area under the curve between models.

SETTING

Bucaramanga, Colombia.

SUBJECTS

Children (n 1261) aged 6-10 years in Tanner stage 1 from a population-based study.

RESULTS

A total of 127 children (seventy girls and fifty-seven boys) were classified with IR, including sixty-three children (thirty-three girls and thirty boys) classified with extreme IR. Only ASF and BMI Z-scores were retained as predictors of IR by stepwise selection. Adding ASF Z-score to BMI Z-score improved the area under the curve from 0·794 (95 % CI 0·752, 0·837) to 0·811 (95 % CI 0·770, 0·851; P for contrast = 0·01). In predicting extreme IR, the addition of ASF Z-score to BMI Z-score improved the area under the curve from 0·837 (95 % CI 0·790, 0·884) to 0·864 (95 % CI 0·823, 0·905; P for contrast = 0·01).

CONCLUSIONS

ASF Z-score predicted IR independent of BMI Z-score in our population of prepubertal children. ASF and BMI Z-scores together improved IR risk stratification compared with BMI Z-score alone, opening new perspectives in the prediction of cardiometabolic risk in prepubertal children.

How useful is BMI in predicting adiposity indicators in a sample of Maya children and women with high levels of stunting?

OBJECTIVES

Body mass index (BMI) is used frequently to estimate adiposity levels in children and adults. However, the applicability of BMI to populations with high levels of stunting has been questioned. Stunted people can have disproportionately short legs, which may increase BMI without increasing body fat because of the relatively larger trunk compared with the legs.

METHODS

A sample of 57 urban Maya schoolchildren, aged 7-9 years (31 boys), and 53 adult women underwent anthropometric assessments and bioelectrical impedance analysis. Multiple linear regression was performed to determine whether the ability of BMI to predict adiposity indicators is altered by stunting and sitting height ratio (SHR). The adiposity indicators were waist circumference, sum of skinfolds, upper arm muscle area, upper arm fat area, and arm fat index.

RESULTS

BMI was the strongest predictor of all adiposity indicators and in most cases, explained more of the variance in adiposity of Maya children than Maya women. Abdominal adiposity was better predicted by BMI than peripheral adiposity in Maya women and Maya children. Stunting was significant in predicting adiposity in some models but never substantially changed the variance explained. SHR was never a significant predictor.

CONCLUSIONS

The relationship between BMI and adiposity indicators is not changed by stunting status or body proportions in this short population of urban Maya children and women. BMI can be used as an indicator of adiposity for these children but not the women. It is recommended that BMI is used in conjunction with other estimates of body composition.

Effect of body mass index on the growth hormone response to clonidine stimulation testing in children with short stature

OBJECTIVES

An inverse relationship has been shown between body mass index (BMI) and the peak growth hormone (GH) response to stimulation in adults and in children with short stature. This relation is observed even within a normal range of BMI. The aim of this study was to investigate the effect of BMI on the GH response to clonidine in a large number of children with short stature.

DESIGN

We conducted a retrospective study on the GH response to clonidine in a single centre.

METHODS

We studied 202 children with short stature (135 M and 67 F) who underwent clonidine testing from 2007 to 2009.

RESULTS

One hundred and twenty-eight patients had a GH peak >10 μg/l. In univariate regression analysis, the peak GH after clonidine was negatively correlated with BMI-standard deviation score (BMI-SDS) and positively correlated with height velocity-SDS and IGF-I-SDS. Only the relationship between peak GH and BMI-SDS remained significant in children with a BMI-SDS from -2 to +2. In the multivariate stepwise regression analysis, BMI-SDS and IGF-I-SDS were the only significant variables in the entire cohort, explaining 19·5% of the variance in peak GH. When only subjects with BMI-SDS between -2·0 and +2·0 were included in the analysis (n = 173), BMI-SDS alone explained 21·4% of the variability in peak GH. The number of patients who failed the clonidine test increased with increasing BMI-SDS.

CONCLUSIONS

BMI affects the GH response to clonidine in children with short stature and should be considered when interpreting the results to the stimulation test.

Nutrition in phenylketonuria

The same basic principles are used to deliver dietary treatment in PKU that was developed sixty years ago. Dietary treatment is undoubtedly very successful, but it has gradually evolved and been guided commonly by individual experience and expert opinion only. There is little international consensus about dietary practice with improvements in specialist dietary products concentrating on taste and presentation rather than nutritional composition. Many areas of dietary treatment have not been rigorously examined. In particular, the amino acid and micronutrient profile of Phenylalanine-free (phe-free) amino acids requires further study. In different formulations of phe-free amino acids, there are variations in the amino acid patterns as well the amount of essential and non essential amino acids per 100g/amino acids. The amount of added tyrosine and branch chain amino varies substantially, and in PKU specifically, there is little data about their relative absorption rates and bioavailability. In phe-free amino acids, there is evidence suggesting that some of the added micronutrients may be excessive and so the source and amount of each micronutrient should be scrutinized, with a need for the development of international nutritional composition standards exclusively for these products. There is a dearth of data about the life-long phenylalanine tolerance of patients or the nutritional state of adult patients treated with diet. There is a growing need to measure body composition routinely in children with PKU and with the rise in childhood obesity, it is important to measure body fatness and identify those who are at greatest risk of 'co-morbidities' of obesity. There is necessity for international collaboration to ensure robust data is collected on many basic aspects of nutritional care to guarantee that diet therapy is delivered to the highest standard.

Validity of body mass index and waist circumference to detect excess fat mass in children aged 7-14 years

BACKGROUND/OBJECTIVES

To evaluate the screening performance of body mass index (BMI) and waist circumference (WC) for excess adiposity. In addition, the diagnostic accuracy of cutoffs from different international and national reference systems based on BMI and WC was investigated.

SUBJECTS/METHODS

Data from 2132 Jena children aged 7-14 years conducted in 2005/2006 were analyzed. Receiver operating characteristic (ROC) curves were constructed to assess BMI and WC, as screening measures for excess adiposity (derived from skinfolds). Sensitivity, specificity and positive predictive values (PPVs) were calculated for two BMI-based classification systems (IOTF and German reference) and sample-based WC cutoffs.

RESULTS

The BMI as well as the WC performed well in detecting excess fat mass, indicated by areas under the ROC curve (AUC) close to 1.0, with slightly greater AUCs for BMI than for WC in both sexes. The specificity of all reference systems was high for both sexes (95 to 98%). However, their sensitivities were low (53-67% in boys; 51-67% in girls). PPV were higher for the German reference and the sample-based WC cutoffs than for the IOTF reference, and higher in girls than in boys.

CONCLUSIONS

The setting in which the reference system should be used is important for the selection of the reference system. The results support the use of the BMI-based references for monitoring in epidemiological studies. The sample-based cutoffs for WC should be refined for clinical use on national level.

Adiposity and cardiovascular risk factors in a large contemporary population of pre-pubertal children

AIMS

to examine the associations of several markers of adiposity and a wide range of cardiovascular risk factors and biomarkers in pre-pubertal children.

METHODS AND RESULTS

four measures of adiposity,body mass index (BMI), waist circumference, dual-energy X-ray absorptiometry (DXA)-determined fat mass, and leptin concentration, were available in up to 7589 children aged 8.8-11.7 (9.9 mean) years from the Avon Longitudinal Study of Parents and Children (ALSPAC). Thirteen per cent of boys and 18.8% of girls were overweight, and 5.3% of boys and 5% of girls were obese. Body mass index was highly correlated with waist circumference (r = 0.91), DXA fat mass (r = 0.87), and leptin concentration (r = 0.75), and all had similar associations with cardiovascular risk factors. A 1 kg/m(2) greater BMI was associated with 1.4 mmHg (95% CI 1.25-1.44) higher systolic blood pressure (BP). In 5002 children, a 1 kg/m(2) greater BMI was associated with a 0.05 mmol/L (95% CI 0.036-0.055) higher non-high-density lipoprotein (HDL) cholesterol and 0.03 mmol/L (95% CI -0.034 to -0.025) lower HDL cholesterol. There were also graded associations with apolipoproteins A1 and B, interleukin-6, and C-reactive protein. Comparing children who were obese with those who were normal weight, the odds ratio for hypertension was 10.7 (95% CI 7.2-15.9) for boys and 13.5 (95% CI 9.4-19.5) for girls.

CONCLUSION

in pre-pubertal UK children, overweight/obesity is common and has broadly similar associations with BP, HDL cholesterol, and non-HDL cholesterol to those observed in adults. Future research should evaluate whether effective interventions to maintain healthy weight in childhood could have important benefits for adult cardiovascular risk.

Effect of body mass index on peak growth hormone response to provocative testing in children with short stature

CONTEXT

Obesity is associated with decreased spontaneous and stimulated GH secretion, but the effect of body mass index (BMI) on results of GH stimulation testing in children with short stature is not known.

OBJECTIVE

The aim of the study was to determine the impact of BMI on peak GH to provocative testing in children with short stature.

DESIGN, SETTING, AND PARTICIPANTS

This was a retrospective review of provocative GH testing performed in 116 children 2-18 yr old in the ambulatory clinic of the Pediatric Endocrinology Unit at the Massachusetts General Hospital from 2004-2008.

MAIN OUTCOME MEASURES

The main outcome measure was peak stimulated GH. Height, weight, IGF-I, and IGF-binding protein 3 were also measured.

RESULTS

In univariate regression analysis, BMI sd score (BMI SDS) was inversely associated with natural log (ln) peak GH to provocative testing (P = 0.002), whereas height SDS, ln IGF-I, and IGF-binding protein 3 were not significantly associated with ln peak GH. After controlling for age, gender, BMI, and pubertal status, BMI (P = 0.002) remained independently associated with ln peak GH. BMI SDS significantly influenced the likelihood of diagnosis of GH deficiency using peak GH cutoffs of 10, 7, and 5 microg/liter.

CONCLUSION

In children with short stature, BMI affects peak stimulated GH and should be considered when interpreting GH testing. Higher BMI SDS, even within the normal range, may lead to overdiagnosis of GH deficiency.