APPLICATION OF BODY MASS INDEX PRINCIPLES IN A MODEL ELEMENTARY SCHOOL: IMPLICATIONS FOR OVERWEIGHT AND OBESE CHILDREN

Journal of the National Medical Association April 1, 2004 | Vieweg, W Victor R; Sood, A Bela; Pandurangi, Anand; Silverman, Joel J The first model elementary school in Richmond, VA formed the study site for this project. Changes in this model will lay the groundwork for changes throughout the Richmond Public School System. Of the 283 students in grades one through five, 66 students (23.3%) were randomly selected. Of the 66 students, 54 (81.8%) were black. Each student underwent height and weight measurement. Using the Nutstat module of the Centers for Disease Control (CDC) Epi Info software program available at no cost on the Internet, we identified Body Mass Index (BMI), BMI percentile for sex and age, and z-score for each student.

Z-score measurements placed the 19 black male children at the 98.08th percentile for BMI (fewer than 2% of U.S. male children were larger). Similarly, the 35 black female children’s BMI was at the 95.35th percentile (fewer than 5% of U.S. female children were larger). Based on data in the literature, the typical black male and female elementary child included in our study can expect a significant reduction in life expectancy compared with their nonobese counterparts. (J Natl Med Assoc. 2004;96:468-475.) Key words: adolescents * anxiety * body mass index * cardiovascular disease * children * depression * diabetes mellitus * elementary school * Epi Info * ethnicity * inner-city schools * growth charts * metabolic syndrome * Nutstat * obesity * overweight * public school * type-2 diabetes mellitus INTRODUCTION Obesity is an ever-increasing problem in the United States. Recent reports describe a 30.5% age-adjusted prevalence rate of obesity for adults.1 Comparable figures for children and adolescents are 10.4% for ages 2-5 years, 15.3% for ages 6-11 years, and 15.5% for ages 12-19 years.2 In a 2003 policy statement of the American Academy of Pediatrics, the Committee on Nutrition discussed the prevention of overweight and obesity in children and adolescents.3 This policy statement emphasized using body mass index (BMI) to assess risk. BMI among children and adolescents is best portrayed using the Centers for Disease Control (CDC) 2000 Growth Charts. These charts relate BMI to percentiles according to sex and age.4,5 An extension of these growth charts is the Nutstat module of Epi Info available on the Internet through the CDC.6 Childhood growth is affected by nutrition, health, and the environment. Historically, clinicians have used height (stature), weight, and head circumference measurements to follow pediatric growth and development. The weight-for-stature charts developed in 1977 (CDC 1978 Growth Charts) are not as useful as the CDC Growth Charts released in 2000 that now include BMI-for-age charts up to the 97th percentile according to sex.

The 1977 weight-for-stature charts were based on limited national survey data for young children. Infant data were derived largely from white middle-class infants from southwestern Ohio. Nearly all infants were formula-fed. Current CDC Growth Charts derive from large national surveys conducted between 1963 and 1994 (mostly between 1963 and 1974) and from supplemental data sources. BMI percentiles, thus, derive from studies completed before the current epidemic of obesity among children and adolescents. site cdc growth charts

The City of Richmond’s first model elementary school provided a favorable setting to test and then implement the Nutstat module of Epi Info as a tool for assessing, following, and intervening in the public health problem of overweight and obesity among children in the United States. The City of Richmond Department of Public Health and the City of Richmond Public School System participated in this study.

METHODS After receiving parental permission, 66 children from grades one through five in the City of Richmond’s first model elementary school were assessed for height and weight (counterweight scale) by the school nurse on March 14, 2003. Students wore their school dress, took off their shoes, and emptied their pockets before being weighed. Additional demographic information obtained included grade in school, birth date, sex, and race. These 66 students were randomly selected from an overall study body of 283 students (first grade: 43, second grade: 50, third grade: 65, fourth grade: 64, and fifth grade: 60 students).

The Nutstat module of Epi Info allows the user to select normative data from 1978 CDC and 2000 CDC figures. In this study, we used the 2000 CDC data. Information entered included birth date, date of measurement, sex, height, and weight. Outcome information included age in months, BMI, percentile, and z-score. Age in months is self explanatory.

BMI is calculated as weight in kg divided by height (stature) in meters squared or as pounds divided by height in inches squared and this value multiplied by 703 to convert to kg/m^sup 2^. In the Nutstat module, the clinician has the option of entering height and weight using either system of measurement. In this study, we entered height in inches and weight in pounds.

Percentile (or percentile rank) reflects BMI rank compared with peers of the same sex and age. Figures 1 and 2 are CDC Growth Charts for BMI for age in percentiles for boy and girls, respectively, ages 2-20 years.4,5 A subject at the 95th percentile in BMI for sex and age has a BMI in the upper 5% of BMI measurements. That is, these are the children that weigh the most for their height.

In a normal (gaussian) distribution, the z-score represents the number of standard deviations (SD) away from the population mean. In other words, it indicates the degree to which an individual’s measurement deviates from what is expected for that individual. Z-scores and percentiles are inextricably linked in the normal (gaussian) distribution, the CDC Growth Charts, and the Nutstat module of Epi Info. Figure 3 depicts the area to the left of a z-score in a normal (gaussian) distribution. Table 1 links z-scores between 0 and 3.5 in increments of 0.5 to percentiles. Z-scores, because of their normal distribution, may appropriately undergo parametric statistical analysis. Z-scores are especially useful for comparing performance on several measures, each with a different mean and SD.

STATISTICS T-statistics were used to compare z-scores.

RESULTS Table 2 outlines the demographics of each of the five classes assessed. Data were obtained from the Nutstat module of Epi Info.6 The ages in months for each grade reflect that this study was completed in the spring of the academic school year. Because the 54 black students made up more than 80% of the student body, we only analyzed data pertaining to them. The remaining 12 students were of Asian, Hispanic, and white background.

Figure 4 shows the percentiles for age and sex of black students at or above the 85th percentile of BMI. More than 50% of all black students met or exceeded the 95th percentile (that is, a z-score of 1.64 or more).

The mean z-score of the 19 black male students was 2.07 ?± 0.90, putting them at the 98.08th percentile. The mean z-score of the 35 black female students was 1.68 ?± 0.93, putting them at the 95.35th percentile. Either with equal variances assumed or equal variances not assumed, differences between male and female z-scores did not reach statistical significance (p value for equal variances assumed was 0.144 and p value for equal variances not assumed was 0.143).

DISCUSSION Our findings support the growing concern about problems of overweight and obesity among school-age children7 and the need to use BMI as a percentile according to sex and age to properly evaluate such students.3 Because our study sample was mostly black students, we will focus on concerns about this portion of the U.S. population. Of the 54 black students evaluated, 48 (88.9%) met current CDC criteria for overweight children or children at risk for overweight (Figure 4).4 More than 50% of all our black students reached or exceeded the 95th percentile of BMI for sex and age.

Ogden et al.2 recently described the prevalence in overweight and risk for overweight among children and adolescents in the United States. For blacks of both sexes and in the age range of 6-11 years, 35.9% were considered overweight or at risk for overweight, and 19.5% were considered overweight compared with our findings of 88.9% (versus 35.9%) and 61.1% (versus 19.5%), respectively. We do not know why our BMI measurements so exceeded the values determined in recent national surveys.

Among our 19 black male children, their mean z-score was at the 98.08th percentile. This means that, using 2000 CDC data, less than 2% of U.S. children and adolescents had greater BMIs than our typical black male student. Among adults, class-3 obesity is defined as a BMI > or =40 kg/m^sup 2^ (Table 3). Currently, class-3 obesity is found nationally among 2.4% of black men8 and may be associated with a reduced life expectancy of up to 20 years for young black men.9 Based on these findings of Fontaine et al.,9 we propose that the typical black male child in our study will experience a significant reduction in life expectancy.

Overweight children are likely to suffer increased long-term morbidity and mortality independent of adult weight after 55 years of follow-up.10 Thus, overweight and risk of overweight during childhood and adolescence constitutes its own special risk independent of the increased risk for adult obesity and its attendant risks. Disease-specific risks for death from coronary heart disease and cancer were particularly evident for male children, and overweight during childhood was more predictive of this increased risk than overweight in adulthood.10 Severely obese children have a lower health-related quality of life than healthy children.11 This quality of life is comparable to those children suffering from cancer.11 Mental health issues include anxiety, depression, and impaired social and psychosocial functioning. Such a compromised quality of life may not only be painful but may interfere with academic performance. go to website cdc growth charts

Eisenberg et al.12 studied 4,746 adolescents (grades seven to 12 at 31 ethnically and socioeconomically diverse public middle and high schools in the urban and suburban school districts of the Minneapolis/St. Paul metropolitan area. They looked for associations between weight-based teasing and body satisfaction, self-esteem, depression, suicidal ideation, and suicide attempts. The authors found that about 30% of adolescent girls and about 25% of adolescent boys reported that peers teased them about their weight. About 29% of adolescent girls and 16% of adolescent boys reported that at least one family member teased them about their weight. About 15% of adolescent girls and 10% of adolescent reported teasing by both peers and family members. Dual-source teasing was most commonly associated with impaired mental health, including a >50% prevalence of suicidal ideation among girls, with 25% of them attempting suicide.

The American Academy of Pediatrics now recommends that clinicians use BMI to identify children and adolescents at risk for obesity.3 Using Figures 1 and 2 will meet these minimum requirements. However, we have provided a detailed outline of the Nutstat module of Epi Info. This tool is freely available on the Internet may be used by clinicians to work with individual students or groups of students to identify, follow, and manage issues of overweight and obesity among children and adolescents. The simplicity, power, and potential benefit of this tool make it an attractive resource.

Various factors have delayed recognizing the importance of overweight and obesity in children and adolescents. Table 3 lists terms now commonly used to describe BMI and obesity in the U.S. population. Inspection of Figures 1 and 2 reveals that children may exceed the 95th percentile for sex and age with a BMI of no more than 18 kg/m^sup 2^ for a four-year old boy or 23 kg/m^sup 2^ for a 10-year-old girl. Such BMI measurements fall well within the “normal” range of BMI measurements for adult men and women. Perhaps parents have assumed that adult guidelines for overweight and obesity apply to their children.

Another way to place BMI and percentiles into adult perspective is for readers to consider adult examples. We selected percentiles and z-scores identical to the mean values of our black children to provide these adult examples. We will use the Nutstat module at age 20 years. For example, an adult man standing 74 inches (six feet, two inches) would reach the 98th percentile of BMI when he weighed 265 pounds (BMI 34.02 kg/m^sup 2^, percentile 98.08, and z-score 2.07). An adult woman standing 64 inches (five feet, four inches) would reach the 95th percentile when she weighed 187.5 pounds (BMI 32.18 kg/m^sup 2^, percentile 95.35, and z-score 1.68).

The current CDC Growth Charts use the terms overweight and risk for overweight rather than obesity and its various grades and classes (Table 3).4 Those children and adolescents with BMIs > or =95th percentile are considered overweight and those > or =85th percentile but <95th percentile are considered to be at risk for overweight. Thus, the shifting terminology used for children, adolescents, and adults may further confuse parents. Using percentiles of BMI for sex and age for children and adolescents may reduce this confusion for parents.

Promoting Healthy Weight Among Elementary School children Chomitz et al.13 recently described their experience in promoting healthy weight among elementary school children using a health report card approach. These investigators conducted a quasi-experimental field trial among 1,396 ethnically diverse children attending four Cambridge, MA elementary schools in 2001-2002. Chomitz el al.13 sought to evaluate family awareness of and concern about their child’s weight status, weight control plans, and preventive measures using a school-based health report card.

Families of children were randomly assigned to three groups. The first group received a personalized weight and fitness health report card (personally informed). The second group received general information about the importance of weight control (generally informed). The third group made up the controls (control group). Chomitz et al.13 assessed outcome using a post-intervention telephone survey. The main outcome measures were: 1) parent’s awareness of child weight status, 2) any concerns, 3) any weight-control plans, and 4) preventive behaviors.

Among overweight children (BMI for sex and age > or =85th percentile), personally informed parents demonstrated the greatest awareness of their child’s weight status compared with generally informed and control group parents. However, 43% of parents of overweight children believed that their child’s weight was healthy. The authors13 acknowledged that more research is needed to test their approach regarding the child’s self-esteem and parental plans for weight control.

Arkansas Experience Prompted by a survey showing that school children in Arkansas suffer from overweight above the national average, state officials enacted a law in April 2003 requiring the state’s 308 public schools to record students’ height and weight and send the results home to parents expressed as BMI along with nutritional advice.14 This initiative will involve 450,000 children and adolescents from kindergarten through grade 12. The Arkansas law bans soft drink and snack sales in elementary schools. A new committee of health and education officials is directed to improve school nutrition and exercise programs.

CONCLUSION Systematic assessment of height and weight in one of Richmond’s public elementary schools uncovered unexpected problems in overweight among its black students. We tested a freely available U.S. Government-sponsored software package that describes the anthropometric profile of children and adolescents. We showed that this software package is both simple and powerful. We plan to repeat our study on a larger scale and employ its principles to identify and follow children and adolescents at risk for overweight and its medical complications. Of concern is the ethical and social implication of how best to provide this information to parents. The other issue that needs exploration is the role that schools may play in the management of obesity beyond their role as educators. The collaboration of schools, health practitioners, and parents may be a natural partnership in making obesity management in children and adolescents a priority.

ACKNOWLEDGEMENTS We wish to acknowledge the support of Delegate Viola O. Baskerville, Superintendent Deborah Jewell-Sherman, Eugene A. Mason Jr., George W. Jones, Sharon F. Jones, Eleanor T. Harrison, the School Board of the City of Richmond, the Richmond City Public Schools, and the City of Richmond, Department of Public Health in bringing this project to fruition.

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11. Schwimmer JB, Burwinkle TM, Varni JW. Health-related quality of life of severely obese children and adolescents. JAMA. 2003;289:1813-1819.

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13. Chomitz VR, Collins J, Kim J, et al. Promoting healthy weight among elementary school children via a health report card approach. Arch Pediatr Adolesc Med. 2003; 157:765-772.

14. McKay B. In Arkansas, schools to score a child’s weight. Wall Street Journal. 2003 Aug 20;B1-B10.

[Author Affiliation] W. Victor R. Vieweg, MD; A. Bela Sood, MD; Anand Pandurangi, MD; and Joel J. Silverman, MD Richmond, Virginia [Author Affiliation] Vieweg, W Victor R; Sood, A Bela; Pandurangi, Anand; Silverman, Joel J