Zuguo Mei

Identifying Risk for Obesity in Early Childhood

OBJECTIVES. Our aim with this study was to assist clinicians by estimating the predictive value of earlier levels of BMI status on later risk of overweight and obesity during the middle childhood and early adolescent years. METHODS. We present growth data from the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development, a longitudinal sample of 1042 healthy US children in 10 locations. Born in 1991, their growth reflects the secular trend of increasing overweight/obesity in the population. Height and weight of participating children in the study were measured at 7 time points. We examined odds ratios for overweight and obesity at age 12 years comparing the frequency with which children did versus did not reach specific BMI percentiles in the preschool- and elementary-age periods. To explore the question of whether and when earlier BMI was predictive of weight status at age 12 years, we used logistic regression to obtain the predicted probabilities of being overweight or obese (BMI ≥85%) at 12 years old on the basis of earlier BMI. RESULTS. Persistence of obesity is apparent for both the preschool and elementary school period. Children who were ever overweight (>85th percentile), that is, ≥1 time at ages 24, 36, or 54 months during the preschool period were >5 times as likely to be overweight at age 12 years than those who were below the 85th percentile for BMI at all 3 of the preschool ages. During the elementary school period, ages 7, 9, and 11 years, the more times a child was overweight, the greater the odds of being overweight at age 12 years relative to a child who was never overweight. Sixty percent of children who were overweight at any time during the preschool period and 80% of children who were overweight at any time during the elementary period were overweight at age 12 years. Follow-up calculations showed that 2 in 5 children whose BMIs were ≥50th percentile by age 3 years were overweight at age 12 years. No children who were <50th percentile for BMI at all points during elementary school were overweight at age 12 years. Children who have higher range BMIs earlier, but not at the 85th percentile, are also more likely to be overweight at age 12 years. Even at time points before and including age 9 years, children whose BMIs are between the 75th and 85th percentile have an ∼40% to 50% chance of being overweight at age 12 years. Children at 54 months old whose BMIs are between the 50th and 75th percentile are 4 times more likely to be overweight at age 12 years than their contemporaries who are <50th percentile, and those whose BMIs are between the 75th and 85th percentile are >6 times more likely to be overweight at age 12 years than those <50th percentile. CONCLUSIONS. The data from this study indicate that children with BMIs >85th percentile, as well as with BMIs in the high reference range are more likely than children whose BMI is <50th percentile to continue to gain weight and reach overweight status by adolescence. Pediatricians can be confident in counseling parents to begin to address the at-risk childs eating and activity patterns rather than delaying in hopes that overweight and the patterns that support it will resolve themselves in due course. Identifying children at risk for adolescent obesity provides physicians with an opportunity for earlier intervention with the goal of limiting the progression of abnormal weight gain that results in the development of obesity-related morbidity.

Relation of BMI to fat and fat-free mass among children and adolescents

OBJECTIVE:Although the body mass index (BMI, kg/m2) is widely used as a surrogate measure of adiposity, it is a measure of excess weight, rather than excess body fat, relative to height. We examined the relation of BMI to levels of fat mass and fat-free mass among healthy 5- to 18-y-olds.METHODS AND PROCEDURES:Dual-energy X-ray absorptiometry was used to measure fat and fat-free mass among 1196 subjects. These measures were standardized for height by calculating the fat mass index (FMI, fat mass/ht2) and the fat-free mass index (FFMI, fat-free mass/ht2).RESULTS:The variability in FFMI was about 50% of that in FMI, and the accuracy of BMI as a measure of adiposity varied greatly according to the degree of fatness. Among children with a BMI-for-age ≥85th P, BMI levels were strongly associated with FMI (r=0.85–0.96 across sex–age categories). In contrast, among children with a BMI-for-age <50th P, levels of BMI were more strongly associated with FFMI (r=0.56–0.83) than with FMI (r=0.22–0.65). The relation of BMI to fat mass was markedly nonlinear, and substantial differences in fat mass were seen only at BMI levels ≥85th P.DISCUSSION:BMI levels among children should be interpreted with caution. Although a high BMI-for-age is a good indicator of excess fat mass, BMI differences among thinner children can be largely due to fat-free mass.

Overweight Among Low-Income Preschool Children Associated With the Consumption of Sweet Drinks: Missouri, 1999–2002

Objective. To examine the association between sweet drink consumption and overweight among preschool children. Methods. A retrospective cohort design was used to examine the association between sweet drink consumption and overweight at follow-up among 10904 children who were aged 2 and 3 years and had height, weight, and Harvard Service Food Frequency Questionnaire data collected between January 1999 and December 2001 and height and weight data collected 1 year later. Sweet drinks included vitamin C-containing juices, other juices, fruit drinks, and sodas as listed on the Harvard Service Food Frequency Questionnaire. Logistic regression was used to adjust for age; gender; race/ethnicity; birth weight; and intake of high-fat foods, sweet foods, and total calories. Results were stratified by baseline BMI. Results. Among children who were normal or underweight at baseline (BMI <85th percentile), the association between sweet drink consumption and development of overweight was positive but not statistically significant. Children who were at risk for overweight at baseline (BMI 85th–<95th percentile) and consumed 1 to <2 drinks/day, 2 to <3 drinks/day, and ≥3 drinks/day were, respectively, 2.0 (95% confidence interval [CI]: 1.3–3.2), 2.0 (95% CI: 1.2–3.2), and 1.8 (95% CI: 1.1–2.8) times as likely to become overweight as the referent (<1 drink/day). Children who were overweight at baseline (BMI ≥95th percentile) and consumed 1 to <2 drinks/day, 2 to <3 drinks/day, and ≥3 drinks/day were, respectively, 2.1, 2.2, and 1.8 times as likely to remain overweight as the referent. Conclusions. Reducing sweet drink consumption might be 1 strategy to manage the weight of preschool children. Additional studies are needed to understand the mechanism by which such consumption contributes to overweight.

Increasing Prevalence of Overweight Among US Low-income Preschool Children: The Centers for Disease Control and Prevention Pediatric Nutrition Surveillance, 1983 to 1995

Objective. To determine whether the prevalence of overweight in preschool children has increased among the US low-income population. Design. Analysis using weight-for-height percentiles of surveillance data adjusted for age, sex, and race or ethnicity. Setting. Data from 18 states and the District of Columbia were examined. a Subjects. Low-income children <5 years of age who were included in the Centers for Disease Control and Prevention Pediatric Nutrition Surveillance System. Results. The prevalence of overweight increased from 18.6% in 1983 to 21.6% in 1995 based on the 85th percentile cutoff point for weight-for-height, and from 8.5% to 10.2% for the same period based on the 95th percentile cutoff point. Analyses by single age, sex, and race or ethnic group (non-Hispanic white, non-Hispanic black, and Hispanic) all showed increases in the prevalence of overweight, although changes are greatest for older preschool children. Conclusion. Overweight is an increasing public health problem among preschool children in the US low-income population. Additional research is needed to explore the cause of the trend observed and to find effective strategies for overweight prevention beginning in the preschool years.

Classification of body fatness by body mass index-for-age categories among children.

OBJECTIVE To examine the ability of various body mass index (BMI)-for-age categories, including the Centers for Disease Control and Preventions 85th to 94th percentiles, to correctly classify the body fatness of children and adolescents. DESIGN Cross-sectional. SETTING The New York Obesity Research Center at St Lukes-Roosevelt Hospital from 1995 to 2000. PARTICIPANTS Healthy 5- to 18-year-old children and adolescents (N = 1196) were recruited in the New York City area through newspaper notices, announcements at schools and activity centers, and word of mouth. MAIN OUTCOME MEASURES Percent body fat as determined by dual-energy x-ray absorptiometry. Body fatness cutoffs were chosen so that the number of children in each category (normal, moderate, and elevated fatness) would equal the number of children in the corresponding BMI-for-age category (<85th percentile, 85th-94th percentile, and > or =95th percentile, respectively). RESULTS About 77% of the children who had a BMI for age at or above the 95th percentile had an elevated body fatness, but levels of body fatness among children who had a BMI for age between the 85th and 94th percentiles (n = 200) were more variable; about one-half of these children had a moderate level of body fatness, but 30% had a normal body fatness and 20% had an elevated body fatness. The prevalence of normal levels of body fatness among these 200 children was highest among black children (50%) and among those within the 85th to 89th percentiles of BMI for age (40%). CONCLUSION Body mass index is an appropriate screening test to identify children who should have further evaluation and follow-up, but it is not diagnostic of level of adiposity.

The prediction of body fatness by BMI and skinfold thicknesses among children and adolescents

Background: Although the body mass index (BMI, kg m−2) is widely used as a measure of adiposity, it is a measure of excess weight, rather than excess body fat. It has been suggested that skinfold thicknesses be measured among overweight children to confirm the presence of excess adiposity. Objective: The present study examined the additional information provided by skinfold thicknesses on body fatness, beyond that conveyed by BMI-for-age, among healthy 5- to 18-years old (n = 1196). Methods and procedures: Total body dual-energy X-ray absorptiometry (DXA) provided estimates of % body fat, and the sum of two skinfolds (triceps and subscapular) was used as an indicator of the overall skinfold thickness. Results: As assessed by the multiple R2s and the residuals of various regression models, information on the skinfold sum significantly ( p < 0.001) improved the prediction of body fatness beyond that obtained with BMI-for-age. For example, the use of the skinfold sum, in addition to BMI-for-age, increased the multiple R2s for predicting % body fat from 0.81 to 0.90 (boys), and from 0.82 to 0.89 (girls). The use of the skinfold sum also reduced the overall prediction errors (absolute value of the residuals) for % body fat by 20–30%, but these reductions varied substantially by BMI-for-age. Among overweight children, defined by a BMI-for-age ≥95th percentile, the skinfold sum reduced the predication errors for % body fat by only 7–9%. Conclusions: Although skinfold thicknesses, when used in addition to BMI-for-age, can substantially improve the estimation of body fatness, the improvement among overweight children is small.

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.

Assessment of iron status in US pregnant women from the National Health and Nutrition Examination Survey (NHANES), 1999–2006

BACKGROUND Total body iron calculated from serum ferritin and soluble transferrin receptor concentrations allows for the evaluation of the full range of iron status. OBJECTIVE We described the distribution of total body iron and the prevalence of iron deficiency (ID) on the basis of total body iron in US pregnant women. DESIGN We examined data from the National Health and Nutrition Examination Survey (NHANES) in 1999-2006 for 1171 pregnant women. RESULTS ID prevalence (±SE) in US pregnant women, which was defined as total body iron <0 mg/kg, was 18.0 ± 1.4%. Pregnant women in the first trimester had a higher mean total body iron than did pregnant women in the second or third trimesters. ID prevalence in pregnant women increased significantly with each trimester (6.9 ± 2.2%, 14.3 ± 2.1%, and 29.5 ± 2.7% in the first, second, and third trimesters, respectively). Pregnant women with parity ≥2 had the lowest mean total body iron and the highest prevalence of ID compared with values for pregnant women with parity of 0 or 1. The ID prevalence in non-Hispanic white pregnant women was significantly lower than in Mexican American or non-Hispanic black pregnant women. The mean total body iron and the prevalence of ID did not differ by educational level or by family income. CONCLUSIONS To our knowledge, these are the first data on total body iron distributions for a representative sample of US pregnant women. Low total body iron is more prevalent in pregnant women in the second or third trimesters, in Mexican American pregnant women, in non-Hispanic black pregnant women, and in women with parity ≥2.

Comparison of the prevalence of shortness, underweight, and overweight among US children aged 0 to 59 months by using the CDC 2000 and the WHO 2006 growth charts.

OBJECTIVE To compare the prevalence of shortness, underweight, and overweight by using the Centers for Disease Control and Prevention (CDC) 2000 and the World Health Organization (WHO) 2006 growth charts. These comparisons are undertaken with 2 sets of cutoff values. STUDY DESIGN Data from the National Health and Nutrition Examination Survey 1999-2004 were used to calculate the prevalence estimates in US children aged 0 to 59 months (n = 3920). Cutoff values commonly used in the United States, on the basis of the 5th percentile of height-for-age to define shortness, the 5th percentile of weight-for-height or weight-for-age to define underweight, and the 95th percentile of weight-for-height or body mass index-for-age to define overweight were compared with the cutoff values recommended by WHO, which use <-2 z-score (equivalent to 2.3rd percentile) to define shortness and underweight and >or=2 z-score (equivalent to 97.7th percentile) to define overweight. A comparison with the same cutoff values (5th and 95th) in the 2 charts was also performed. RESULTS Applying the 5th or 95th percentile, we observed a higher prevalence of shortness and overweight for all the age groups when the WHO 2006 growth charts were used than when the CDC 2000 growth charts were used. Applying the 5th percentile to the WHO 2006 charts produced lower rates of underweight than did the CDC 2000 charts. However, applying the 5th or 95th percentiles to the CDC 2000 charts and the WHO-recommended cutoff values of -2 or +2 z-score to the WHO charts produced smaller differences in the prevalence of shortness and overweight than were seen when the 5th and 95th percentiles were applied to both the CDC and WHO charts. CONCLUSIONS Estimates of the prevalence of key descriptors of growth in children aged 0 to 59 months vary by the chart used and the cutoff values applied. The use of the 5th and 95th percentiles for the CDC growth charts and the 2.3rd and 97.7th percentiles for the WHO growth charts appear comparable in the prevalence of shortness and overweight, but not underweight. If practitioners were to use the WHO growth charts, it might be more appropriate to adopt the WHO recommended cutoff values as well, but this would be a change for office practice.

Do Skinfold Measurements Provide Additional Information to Body Mass Index in the Assessment of Body Fatness Among Children and Adolescents

OBJECTIVES. The purpose of this work was to validate the performance of age- and gender-specific BMI, triceps, and subscapular skinfold for the classification of excess of body fat in children and adolescents and to examine how much additional information these 2 skinfold measurements provide to BMI-for-age. METHODS. The receiver operating characteristic curve was used to characterize the sensitivity and specificity of these 3 indices in classifying excess body fat. Percentage of body fat was determined by dual-energy radiograph absorptiometry. Both ≥85th and ≥95th percentile of percentage of body fat were used to define excess body fat. Data from the New York Pediatric Rosetta Body Composition Project were examined (n = 1196; aged 5–18 years). RESULTS. For children aged 5 to 18 years, BMI-for-age, triceps skinfold-for-age, and subscapular skinfold-for-age each performed equally well alone in the receiver operating characteristic curves in the identification of excess body fat defined by either the 85th or 95th percentile of percentage of body fat by dual-energy radiograph absorptiometry. However, if BMI-for-age was already known and was >95th percentile, the additional measurement of skinfolds did not significantly increase the sensitivity or specificity in the identification of excess body fat. CONCLUSIONS. In contrast to the recommendations of expert panels, skinfold measurements do not seem to provide additional information about excess body fat beyond BMI-for-age alone if the BMI-for-age is >95th percentile.