APPLICATION OF BODY MASS INDEX PRINCIPLES: DISCUSSION

18 Dec
2009

APPLICATION OF BODY MASS INDEX

Our findings support the growing concern about problems of overweight and obesity among school-age children and the need to use BMI as a percentile according to sex and age to properly evaluate such students. 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). More than 50% of all our black students reached or exceeded the 95th percentile of BMI for sex and age.

Ogden et al. 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.
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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 >40 kg/m2 (Table 3). Currently, class-3 obesity is found nationally among 2.4% of black men and may be associated with a reduced life expectancy of up to 20 years for young black men. Based on these findings of Fontaine et al., 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. 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.

Severely obese children have a lower health-related quality of life than healthy children. This quality of life is comparable to those children suffering from cancer. 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.
Eisenberg et al. studied 4,746 adolescents (grades seven to 12 at 31 ethnically and socioeco-nomically 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. 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/m2 for a four-year old boy or 23 kg/m2 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. Viagra Online Canadian Pharmacy

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/m2, 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/m2, 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). Those children and adolescents with BMIs >95th percentile are considered overweight and those >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. 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. 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.
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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. 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 >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 authors acknowledged that more research is needed to test their approach regarding the child’s self-esteem and parental plans for weight control.
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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. 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.

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