Racial/ethnic differences in body fatness among children and adolescents

Background: Although the BMI is widely used as a measure of adiposity, it is a measure of excess weight, and its association with body fatness may differ across racial or ethnic groups. Objective: To determine whether differences in body fatness between white, black, Hispanic, and Asian children vary by BMI‐for‐age, and whether the accuracy of overweight (BMI‐for‐age ≥ Centers for Disease Control and Prevention (CDC) 95th percentile) as an indicator of excess adiposity varies by race/ethnicity. Methods and Procedures: Total body dual‐energy X‐ray absorptiometry (DXA) provided estimates of %body fat among 1,104 healthy 5‐ to 18‐year‐olds. Results: At equivalent levels of BMI‐for‐age, black children had less (mean, 3%) body fatness than white children, and Asian girls had slightly higher (1%) levels of %body fat than white girls. These differences, however, varied by BMI‐for‐age, with the excess body fatness of Asians evident only among relatively thin children. The ability of overweight to identify girls with excess body fatness also varied by race/ethnicity. Of the girls with excess body fatness, 89% (24/27) of black girls, but only 50% (8/16) of Asian girls, were overweight (P = 0.03). Furthermore, the proportion of overweight girls who had excess body fatness varied from 62% (8/13) among Asians to 100% (13/13) among whites. Discussion: There are racial or ethnic differences in body fatness among children, but these differences vary by BMI‐for‐age. If race/ethnicity differences in body fatness among adults also vary by BMI, it may be difficult to develop race‐specific BMI cut points to identify equivalent levels of %body fat.     

Nutritional assessment by mid-upper arm circumference of santal adults of Purulia, West Bengal, India

The present community based cross-sectional study was undertaken to determine the prevalence of undernutrition using mid-upper arm circumference (MUAC) among adult (> 18 years) Santals of Purulia District, West Bengal, India. It was undertaken at 10 villages of the district. A total of 520 (217 males and 303 females) subjects were measured. Commonly used indicator i.e., MUAC and BMI, were used to evaluate the nutritional status of the subjects. More women (64.7%) then men (54.4%) based on MUAC and women (59.4%) then men (34.6%) based on BMI were undernourished. Significant sex difference both in MUAC (t=2.378, p<0.05) and BMI (t=4.971, p<0.001) were observed. Significant age group difference for MUAC was observed (F=8.93***, df=3) for men and (F=9.52***, df=3) for women. For BMI, these values were F=10.10*** (df=3) F=6.17*** (df=3) respectively. In conclusion, we found that adult Santals of both sexes were under critical nutritional stress, women and the oldest among them were the most.     

Adiposity,central body fat distribution and blood pressure among young Bengalee adults of Kolkata,India: sexual dimorphism

A cross-sectional study of 174 men and 153 women of Bengalee ethnicity was undertaken to compare levels of adiposity, central body fat distribution and blood pressure. The mean age of both the sexes were similar (men = 20.1 years; women = 20.0 years). Significantly more women (n = 42, 27.5%) were overweight (body mass index, BMI > or = 25.0 kg/m2) as compared with men (19, 10.9%). Men were significantly taller and heavier. They also had significantly greater mean waist (WC) and mid upper arm (MUAC) circumferences compared with women. On the other hand, women had significantly (p < 0.001) greater mean BMI, biceps (BSF), triceps (TSF) and subscapular (SSF) skinfolds. The mean values of systolic (SBP), diastolic (DBP) and mean arterial (MAP) blood pressure were significantly greater among men. These significant differences existed even after controlling for BMI. Regression analyses revealed that sex had significant effect on all these variables even after controlling for BMI. Correlation studies showed that WC was found to be much more strongly correlated than BMI with SBP, DBP and MAP, in both sexes. However, when the effect of WC (along with BMI) was also controlled for, there was no significant sex difference in blood pressure.     

Age-sex and diurnal variation of blood pressure in different nutritional states among the adult Telegas of Kharagpur in West Bengal, India

An anthropological investigation among the endogamous Telega population (106 adult individuals including 51 males and 55 females) in the district of Paschim Medinipur of West Bengal, India shows wide range of age-sex as well as diurnal variation of mean blood pressure (MBP) with reference to different nutritional status. Distribution of MBP shows distinct bias for sexes separately on different occasions and in association with age and other physiological conditions like menopause in females. Records of increase of blood pressure from morning to evening also indicate clear diurnal change in both male as well as in the female samples with some variations when compared between the two sexes. Results also help us to understand and to record the variation of blood pressure as a physiometric trait in the population under study. Data indicate that nearly 30% of males and more than 30% of females are living at the level of undernutrition. Nutritional status is measured by anthropometric measurements, e.g. height, weight, mid arm circumference (MUAC) and further calculation of body mass index (BMI). Distribution of MBP at different BMI and MUAC levels and Pearson correlation and regression analysis--all suggest that age, BMI and MUAC have significant impacts on BMI with some sex-related variations.     

Fat patterning in Papua New Guineans: effects of age, sex and acculturation

For the renewed interest in fat patterning to be fruitful, more information on the biology of fat patterning, particularly normative data are required. Nine skinfold thicknesses were measured in 2312 coastal and highland Papua New Guineans of all ages undergoing acculturation. Principal component analysis of the skinfold data revealed components of fatness and fat patterning. First component scores were typical of the changes in fatness with age and the sex differences expected in these populations. Second component scores of limb-trunk fat patterning showed marked changes with age in both sexes but they stabilised in adulthood. This pattern seemed more affected by maturity although it is usually thought to be a sex-specific pattern. The third component, upper-lower body patterning, was more sexually dimorphic in adults. Marked differences were not observed between the two communities but over a 15-year period fatness levels increased slightly and subcutaneous fat tended to be deposited more centrally.     

Gender differences in fat patterning in children living in Ankara

Body composition is an excellent indicator for assessing obesity and nutritional status of both individuals and populations. Youth obesity has important health and social implications, because a large proportion of adult obesity has its origin in childhood. Numerous studies report that adverse levels of cardiovascular diseases risk factors are associated with adiposity in children. Concerning the Turkish population there is up to now only limited information with regard to adiposity in children. The aim of this study was therefore to determine the anthropometric and body composition characteristics and to investigate sex differences in fat patterning including fat distribution in a group of children living in Ankara. The present study evaluated the body composition of 332 boys and 269 girls aged between 8 and 11 years, attending public schools. It was carried out by a cross-sectional study and was focused on that anthropometric variables, which reflect body fat and fat-free mass. Anthropometric measurements including height, weight, triceps and subscapular skinfolds thickness were carried out on these children. The body mass index (BMI) was also calculated. The measurements were used to estimate the two-compartment model of body composition: fat-free mass (FFM) and body fat (BF) from skinfold equations. The mean fat percentage in boys is highest at 11 years (16.8%) and lowest at 10 years (15.6%). In girls these figures come to 18.2% and 17.1%, respectively. Girls of these age groups have a significantly larger percentage of body fat and skinfold thickness. At this young age there is therefore clear evidence of sexual dimorphism in fat patterning, as girls are showing a greater subcutaneous adiposity, which is mainly contributed by the triceps fat. The body fat (kg) increases in both sexes all over the investigated age groups. The Pearson correlation matrix showed a high significant relation between the anthropometric measurements (p < 0.01). The present study confirms the findings that sexual dimorphism of fat patterning in children is to be seen in the age of 8 - 11 years. It furthermore presents basic data of body composition, which could serve as reference data in other studies on the Turkish population.     

The shape of things to come? household dependency ratio and adolescent nutritional status in rural and urban Ethiopia

Several related demographic trends are occurring in developing countries: youth comprise a large portion of populations, fertility rates are declining, and urban dwellers are increasing. As fertility rates decline and populations age, the decline in the ratio of young dependents to working age adults is expected to free up household resources, which can be invested in human capital, including youth nutritional wellbeing. We test this hypothesis in a sample of youth (n = 1,934) in Southwestern Ethiopia. Multiple measures of achieved growth and nutritional status are explored (weight, height, mid-upper arm circumference (MUAC), body mass index (BMI) and body mass index for age z-score (BMIZ), weight for age z-score (WAZ), and height for age z-score (HAZ)). In multivariable models controlling for the effects of income, age, gender, and youth workloads, youth living in rural settings had significantly lower weight (1.24 kg lighter), MUAC (0.67 cm lower), BMI (0.45 BMI lower), BMIZ (0.27 lower), HAZ (0.14 HAZ lower), and WAZ (0.3 WAZ lower) than urban youth (all P < 0.01). Compared with youth in the lowest dependency ratio households, results show that youth in households with the highest dependency ratios were estimated to be 1.3 kg lighter, have 0.67 cm smaller MUAC, and BMI that was 0.59 lower (all P<0.01). Similar results were found for WAZ (0.21 lower) and BMIZ (0.36 lower). Youth height and HAZ were not associated with household dependency. These results may point toward increasing levels of human capital investments in Ethiopian youth as fertility levels decline and populations urbanize.     

Baseline Correlates of Insulin Resistance in Inner City High‐BMI African‐American Children

To characterize the influence of diet‐, physical activity–, and self‐esteem‐related factors on insulin resistance in 8–10‐year‐old African‐American (AA) children with BMI greater than the 85th percentile who were screened to participate in a community‐based type 2 diabetes mellitus (T2DM) prevention trial. In 165 subjects, fasting glucose‐ and insulin‐derived values for homeostasis model assessment of insulin resistance (HOMA‐IR) assessed insulin resistance. Body fatness was calculated following bioelectrical impedance analysis, and fitness was measured using laps from a 20‐m shuttle run. Child questionnaires assessed physical activity, dietary habits, and self‐esteem. Pubertal staging was assessed using serum levels of sex hormones. Parent questionnaires assessed family demographics, family health, and family food and physical activity habits. Girls had significantly higher percent body fat but similar anthropometric measures compared with boys, whereas boys spent more time in high‐intensity activities than girls. Scores for self‐perceived behavior were higher for girls than for boys; and girls desired a more slender body. Girls had significantly higher insulin resistance (HOMA‐IR), compared with boys (P < 0.01). Adjusting for age, sex, pubertal stage, socioeconomic index (SE index), and family history of diabetes, multivariate regression analysis showed that children with higher waist circumference (WC) (P < 0.001) and lower Harter's scholastic competence (SC) scale (P = 0.044) had higher insulin resistance. WC and selected self‐esteem parameters predicted insulin resistance in high‐BMI AA children. The risk of T2DM may be reduced in these children by targeting these factors.     

Fat, muscles, and wages

Recent studies in health economics have generated two important findings: that as a measure of fatness the body mass index (BMI) is biased; and that, when it comes to analyzing wage correlates, both fat-free mass (FFM) and body fat (BF) are better suited to the task. We validate these findings for Germany using the BIAdata Base Project and the German Socio-Economic Panel. While we find no significant correlation between BMI and wages in any of our models, simple linear regression models featuring both contemporary and time-lagged fatness measures indicate that FFM and, to a lesser extent, BF are associated with hourly wages: more specifically, the relationship between FFM/BF and hourly wages is about two to three times higher for females than for males. In contrast, fixed-effects models indicate that there is no correlation between hourly wages and both FFM and BF with one exception: a significant correlation (and one in line with expectations) is found to be the rule among job changers.     

Body Composition Percentiles in Urban South Indian Children and Adolescents

Objective

This study aimed to generate age‐ and sex‐specific percentiles for body composition indices in children and to assess the variability in these indices, in relation to BMI.

Methods

Anthropometry and body fat were measured with the BOD POD (Cosmed; Rome, Italy) in 9,702 children from Bangalore, India. Smoothed percentile curves using the lambda‐mu‐sigma method were obtained for BMI, fat‐free mass index (FFMI), fat mass index (FMI), and body fat percentage (% BF).

Results

Percentile curves for % BF and FMI in boys increased from 6 to 12 years and declined from 13 years on, while in girls, it increased until 15 years. The FFMI percentile curves increased with age in both sexes. The mean FMI declined from 12 years on in boys, corresponding to a large increase in FFMI from that age, while in girls, both FMI and FFMI continued to increase. The 75th percentile of % BF and FMI had greater sensitivity to identify children with obesity.

Conclusions

This study developed smoothed percentile curves for body composition in Indian children and suggests FMI and FFMI as good indicators of growth in children.

     

The Body Adiposity Index (Hip Circumference ÷ Height1.5) Is Not a More Accurate Measure of Adiposity Than Is BMI,Waist Circumference,or Hip Circumference

Based on cross‐sectional analyses, it was suggested that hip circumference divided by height^1.5 ?18 (the body adiposity index (BAI)), could directly estimate percent body fat without the need for further correction for sex or age. We compared the prediction of percent body fat, as assessed by dual‐energy X‐ray absorptiometry (PBF_DXA), by BAI, BMI, and circumference (waist and hip) measurements among 1,151 adults who had a total body scan by DXA and circumference measurements from 1993 through 2005. After accounting for sex, we found that PBF_DXA was related similarly to BAI, BMI, waist circumference, and hip circumference. In general, BAI underestimated PBF_DXA among men (2.5%) and overestimated PBF_DXA among women (4%), but the magnitudes of these biases varied with the level of body fatness. The addition of covariates and quadratic terms for the body size measures in regression models substantially improved the prediction of PBF_DXA, but none of the models based on BAI could more accurately predict PBF_DXA than could those based on BMI or circumferences. We conclude that the use of BAI as an indicator of adiposity is likely to produce biased estimates of percent body fat, with the errors varying by sex and level of body fatness. Although regression models that account for the nonlinear association, as well as the influence of sex, age, and race, can yield more accurate estimates of PBF_DXA, estimates based on BAI are not more accurate than those based on BMI, waist circumference, or hip circumference.     

Presence of high rates of overweight and obesity among adult Marwaris of Howrah, West Bengal, India

A cross-sectional study of 220 (110 men and 110 women) adult (> 20 years) Marwaris of Howrah, West Bengal, India, was undertaken to investigate the frequency of overweight and obesity, using different criteria. Results revealed that men had significantly greater mean height, weight, waist circumference (WC), waist-hip ratio (WHR), conicity index (CI) and fat free mass (FFM), compared with women. Women had significantly higher mean body mass index (BMI), biceps (BSF) and triceps (TSF) skinfolds, mid-upper arm (MUAC) and hip (HC) circumferences, percent body fat (PBF), fat mass index (FMI), mid-arm fat area (MAFA) and PBF/BMI ratio compared with men. The frequency of overweight (BMI > or = 25.0) was significantly higher among women (71.8%) compared with men (44.5%). Similarly, significantly more women (41.8%) had high WHR than men (22.7%). Significantly more women also had high PBF (97.3%) compared with men (90.9%). In conclusion, these results demonstrated that the level of overall and central adiposity, as well as body fat, was found to be high among Marwaris, as compared with other ethnic populations of India. Moreover, there existed significant sexual dimorphism in these measures among this ethnic group. This high level of overall and central adiposity and body fat could have severe adverse health implications in this ethnic group.     

Blood lead level and nutritional status indicators in preadolescent Polish schoolchildren

BackgroundEnvironmental pollutions with heavy metals may have toxic effects on human health and development. One of the most detrimental is lead exposure, which may disturb neurodevelopment and linear growth in children. However, data on the effect of lead exposure on nutritional and weight status in children are limited, thus this study aimed to assess the effect of blood lead (Pb) level on nutritional and weight status in preadolescent schoolchildren from the industrialized, mining region in southwestern Poland.MethodsOur study sample involved N = 709 schoolchildren (402 boys and 307 girls) in the preadolescent developmental period (7–11 years of age for boys and 7–10 years of age for girls). Anthropometric measurements were used to assess nutritional and weight status: body mass index (BMI), mid-upper arm circumference (MUAC) and skinfolds thicknesses (triceps, subscapular, abdominal and the sum of skinfolds). Blood Pb level was evaluated and divided into two groups: above (>3.7 μg/dL) and below median value (≤3.7 μg/dL).ResultsAnalysis of covariance (with children’s age controlled as a covariate) revealed that children with blood Pb level above median value had significantly lower values of BMI, MUAC and all skinfolds (at least p < 0.01). However, this effect was significant only in boys, whereas in girls differences were non-significant (p > 0.05). The highest effect size of blood Pb level was noted for skinfolds thicknesses (partial η²: 0.015 for the sum of skinfolds).ConclusionsNutritional status in children with higher blood Pb level is significantly impaired in preadolescent boys, who appear to be more sensitive to this environmental factor. Our findings indicate a particular need for nutritional and environmental interventions among preadolescent children in regions with higher lead exposure.     

Human Body Composition and the Epidemiology of Chronic Disease

Obesity and body fat distribution (FD) are established risk factors for chronic diseases. The body mass index (BMI) and the waist/hip circumference ratio (WHR) are used conventionally as indices of obesity and FD in epidemiological studies. Although some general limitations of these indices are recognized, others that affect their use in relative risks for disease are not well recognized. These include effects of sex, ethnicity, and especially age on the relationships between these indices and body composition, which can result in substantial misclassification of obesity and FD. There is considerable variability in body composition for any BMI, and some individuals with low BMIs have as much fat as those with high BMIs. This results in poor sensitivity for classifying levels of body fatness (e.g., too many “false negatives,” or overweight individuals classified as not overweight), and relative risks are attenuated across all categories of BMI. A more serious problem, however, is that at different ages the same levels of BMI correspond to different amounts of fat and fat-free mass. Data from the Rosetta Study and the New Mexico Aging Process Study show that older adults have, on average, more fat than younger adults at any BMI, due to the loss of muscle mass with age. As a result, the sensitivity of BMI cutpoints with respect to body fatness decreases with age, and the use of a fixed cutpoint for all ages results in “differential mis-classification bias.” Taken together, these issues sug- gest that the increases with age in the prevalences of overweight and obesity, and in the risks for chronic diseases, may be mis-estimated using BMI. Similar issues may affect the use of WHR for estimating prevalences and associated risks of FD. New field methods for estimating body composition are available that can be applied in large, epidemiologic follow-up studies of chronic diseases. These methods will allow epidemiologists to consider, for example, whether it is increased fat, or the replacement of fat-free mass with fat, with age that is associated with risk for chronic disease.     

Comparisons of fatness indicators in Budapest children

The aim of this study was to estimate the fatness level of Budapest children and youth in different ways and to compare these estimations using a large representative sample. Eighteen body measurements were taken on 2606 healthy boys and 2471 healthy girls aged between 3 and 18 years. About 20% of this sample was measured by the Futrex 5000A near infrared (NIR) spectrophotometer to assess the body fat percent (data of 419 boys and 462 girls aged between 5 and 18 years were analysed). Triceps skinfold thickness (TSF), sum of triceps, medial calf, subscapular and suprailiac skinfold thicknesses (SFS), body fat percent estimated according to Slaughter et al. (%BF), BMI (calculated from height and weight) and body fat percent assessed by NIR-method (NIR%BF) were compared. chi 2 tests of independence show significant connections among the distributions ranged by the five fatness indicators. However, correlation coefficients and standard errors indicate that strong relationships are only among the assessments based on skinfold thicknesses (r = 0.92-0.97, SEE = 1.8-2.6%). BMI and NIR%BF assess body fatness differently compared to skinfold thicknesses: r-values are moderate and SEE-values are relatively large (r = 0.59-0.87, SEE = 1.9-4.7%). These findings can be seen in both the boys and the girls. NIR%BF comparing to %BF significantly overpredicts body fat percent in the boys and significantly underpredicts it in the girls. BMI, height and weight are not in significant correlation with NIR%BF in the boys but there are moderate correlations in the girls. Our suggestion is that more research is needed with the use of NIR-method in children and adolescents, and it is necessary to refine prediction equations taking into consideration very carefully sex sand age differences.     

Rates of lipogenesis and plasma insulin concentrations in inbred lines of mice differing in fatness

Rates of lipogenesis de novo and plasma concentrations of insulin were compared during post-natal growth in two inbred lines of mice (VL/fDk (VL) and SWR/fNIMR (SWR] in which differences in growth and fatness are probably due to multiple not single gene effects. Irrespective of sex, the lipogenic rate/g was higher in the fatter VL mice in the liver and all other tissues except the head, where it was lower, and the gonadal fat pad, where it was not different. Adult mice in general had lower lipogenic rates than those measured soon after weaning. In both lines the lipogenic rate/g of tissue was higher in males in the liver and in females in the gonadal fat pad. Plasma insulin concentrations were higher in VL mice and tended to rise with age. These results demonstrate that metabolic differences associated with differences in fatness in inbred lines of mice in which fatness is controlled by more than one gene, are qualitatively but not quantitatively similar to those observed by other workers in lines of mice differing in fatness due to a single gene mutation.     

Subcutaneous fat remodelling in Southeast Asian infants and children

Longitudinal data on 1,048 Thai children were evaluated for evidence of subcutaneous fat remodelling. Fat distribution, as defined by 100 (triceps/[triceps + subscapular]), was more pronounced in the limbs during infancy but shifted toward the trunk thereafter. Subsequent stepwise regression analysis indicated that biological age--as measured by Gruelich-Pyle bone age--and weight together explained between 0.8% and 14.5% of variance in fat distribution, with generally larger R2 values over age and for males. Relationships were curvilinear, with sex differences in slope. Path analysis supported the model that weight was a major causal agent primarily after infancy, whereas biological age had a small influence both in infancy and in late childhood. These findings indicate that trunk fat deposition is a normal feature of childhood. They also suggest that hypotheses which associate elevated trunk fatness with disorders of glucose metabolism are invalid for younger children.     

Quantitative Support for a Subjective Fatness Index for Immobilized Polar Bears

ABSTRACT Adequate stores of body fat are essential for survival and reproduction of polar bears (Ursus maritimus). However, polar bear body fat levels can be difficult to quantify in the field. For >30 years, biologists have subjectively estimated relative fatness of immobilized polar bears by assigning individuals a rating from 1 to 5, with 1 being leanest and 5 most obese. Although previous studies suggested this fatness index (FI) rating accurately reflects large-scale differences in body condition, its relationship to more quantitative measures of condition has not been explored. We compared the FI rating of individual polar bears in western Hudson Bay and the Beaufort Sea to 2 quantitative measures of body condition: the Quetelet Index (ratio of mass to length²) and the relative lipid content of adipose tissue. We found a significant relationship between FI rating and both Quetelet Index values and adipose lipid content. Our data demonstrate that the FI rating accurately reflects overall body condition, regardless of polar bear age, sex, or nutritional phase. We suggest that continued field use of the FI rating could provide valuable information on ecological effects of large-scale environmental change on polar bear populations.     

Socioeconomic status, sex, age, and ethnicity as determinants of body fat distribution for Guatemalan children

The distribution of subcutaneous fat at the triceps and subscapular skinfold sites is described for four groups of children living in Guatemala. These groups are high socioeconomic status (SES) children of Ladino (mixed Spanish and Indian) ancestry, high SES children of European ancestry, low SES Ladino children, and very low SES Indian children. The method of Healy and Tanner (1981) is used, employing regression and principal components analysis of log transformed skinfold values to divide "fatness" into two uncorrelated variables: size (amount of fat) and shape (fat pattern). Significant differences exist between groups in size, with lower SES groups having less fat than higher SES groups. No significant difference in fat pattern exists between the high SES Ladino and high SES European children. Significant differences do exist between the high SES groups and the low SES groups. The relative amount of subscapular fat increases from the high SES Ladinos and high SES Europeans, to the low SES Ladinos, to the very low SES Indians. In the high SES European and high SES Ladino samples, girls have significantly more arm fat than boys. There is no significant difference in fat patterning between boys and girls in the two low SES samples. Finally, the relative amount of subscapular fat tends to increase with age in all four samples. These results indicate that fatness and fat patterning are independent anatomical characteristics, SES influences fat patterning; low SES children of both Ladino and Indian ancestry show greater reductions in arm fat than in trunk fat compared to high SES children, sexual dimorphism in fat patterning is SES dependent.(ABSTRACT TRUNCATED AT 250 WORDS)     

Which Metric of Relative Weight Best Captures Body Fatness in Children?

Objective: To evaluate the relative merits of BMI (kilograms per meter squared) and age‐ and gender‐adjusted BMI, age‐ and gender‐specific z score of BMI, and age‐ and gender‐specific percentiles of BMI as surrogate measures of body fatness among a sample of youth. Research Methods and Procedures: The sample comprised 596 children and adolescents 5 to 18.7 years old and was 40% male and 55% white. Height and weight were measured by trained research staff. DXA was used to determine body fat mass. BMI, age‐ and gender‐specific percentile of BMI, and age‐ and gender‐specific z scores of BMI were computed, and these metrics were compared with measured body fatness. Results: The BMI values in the sample ranged from 12.9 to 55.0 kg/m², with a mean of 24.9 kg/m². The Spearman correlations with percentage body fat were similar for all of the BMI metrics (r = 0.82 to 0.88). Linear regression models with age‐ and gender‐specific percentiles of BMI explained significantly less of the variance (65%) than models with log‐transformed BMI (81%) or age‐ and gender‐specific z scores of BMI (75% to 79%). z scores were the most accurate at classifying children who were overfat (sensitivity = 0.84, specificity = 0.96 for z score ≥1). However, using a BMI ≥85th percentile or a BMI ≥20 kg/m² was also accurate at classifying youth. Discussion: The BMI metrics had similar correlations with body fatness, but age‐ and gender‐specific percentiles of BMI were the least accurate proxy measure of body fatness. However, a BMI z score ≥1, BMI percentile ≥85, and BMI ≥20 kg/m² are all useful for identifying children who may be overfat.