BMI Measurement in Schools

CONTRIBUTORS: Allison J. Nihiser, MPH,a Sarah M. Lee,
PhD,a Howell Wechsler, EdD,a Mary McKenna, PhD,b Erica
Odom, MPH,a Chris Reinold, PhD, RD,c Diane Thompson,
MPH, RD,c and Larry Grummer-Strawn, PhDc
Divisions of aAdolescent and School Health and cNutrition,
Physical Activity, and Obesity, Centers for Disease Control and
Prevention, Atlanta, Georgia; and bDepartment of Kinesiology,
University of New Brunswick, Fredericton, New Brunswick,
Canada
KEY WORDS
body mass index, obesity, growth and development, school
health services, child, adolescent
ABBREVIATIONS
CDC—Centers for Disease Control and Prevention
IOM—Institute of Medicine
AAP—American Academy of Pediatrics
This article is based on a longer article first published in the
Journal of School Health (Nihiser AJ, Lee SM, Wechsler H, et al.
Body mass index measurement in schools. J Sch Health. 2007;
77[10]:651– 671; quiz 722–724).
The findings and conclusions in this report are those of the
authors and do not necessarily represent the official position of
the Centers for Disease Control and Prevention.
www.pediatrics.org/cgi/doi/10.1542/peds.2008-3586L
doi:10.1542/peds.2008-3586L
Accepted for publication Apr 29, 2009
Address correspondence to Allison J. Nihiser, MPH, Centers for
Disease Control and Prevention, Division of Adolescent and
School Health, 4770 Buford Hwy NE, Mailstop K-12, Atlanta, GA

  1. E-mail: anihiser@cdc.gov
    PEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, 1098-4275).
    Copyright © 2009 by the American Academy of Pediatrics
    FINANCIAL DISCLOSURE: The authors have indicated they have
    no financial relationships relevant to this article to disclose.
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    Obesity among youth has become 1 of
    the most critical public health problems
    in the United States. Schools can
    play an important role in preventing
    obesity because 95% of young people
    are enrolled in schools,1 and
    schools have historically promoted
    physical activity and healthy eating. Research
    has shown that well-designed,
    well-implemented school-based programs
    can effectively promote these
    behaviors,2–4 and the Centers for Disease
    Control and Prevention (CDC) has
    identified strategies that schools can
    use to prevent obesity.5
    Measuring the BMI of students in
    schools is an approach to addressing
    obesity that is attracting attention
    across the nation from researchers,
    school officials, legislators, and the
    media.6–12 Because little research has
    been conducted on the impact of this
    approach, it is not included in the
    CDC’s recommended strategies. However,
    some states, cities, and communities
    have established school-based
    BMI-measurement programs in recent
    years, and many others are considering
    the merits of initiating such programs.
    In 2005, the Institute of Medicine (IOM)
    called on the federal government to develop
    guidance for BMI-measurement
    programs in schools.13 The CDC conducted
    an extensive search for scientific
    studies that evaluated school-based
    BMI-measurement programs; collected
    related position statements
    published by expert organizations
    from public health, medicine, and education;
    and reviewed sources to identify
    state legislation on these programs
    including policy-tracking
    services, state general assembly legislative
    databases, and staff in state education
    or health departments.14–18 An
    expert panel, convened by the CDC in
    2005, provided input on an earlier version
    of this article. The panel comprised
    experts in public health, education,
    school counseling, school
    medical care, and parenting. This article
    presents an overview of the CDC’s
    guidance on this topic; it describes the
    purposes of BMI-measurement programs,
    examines current practices,
    reviews existing research, summarizes
    expert recommendations, identifies
    research gaps, and provides guidance
    and safeguards for implementing
    BMI-measurement programs.
    PURPOSES OF COLLECTING BMI
    DATA
    BMI is the ratio of an individual’s
    weight to height squared (kg/m2) and
    is used to estimate a person’s risk of
    weight-related health problems. It is
    often used to assess weight status, because
    it is relatively easy to measure
    and correlates with body fat.19–23 After
    BMI is calculated for a child or adolescent,
    it is plotted by age on a genderspecific
    growth chart (see www.cdc.
    gov/growthcharts for the CDC’s BMIfor-
    age growth charts for girls and
    boys aged 2–20 years). BMI measurement
    in schools may be conducted for
    surveillance and screening purposes.
    Surveillance
    Surveillance refers to the systematic
    collection, analysis, and interpretation
    of data from a census or representative
    sample (ie, a sample that has been
    scientifically selected to represent a
    specified population). Typically, the
    data are collected anonymously. The
    purpose of BMI surveillance in schools
    is to identify the percentages of students
    in the population who are obese,
    overweight, normal weight, and underweight;
    surveillance does not involve
    informing parents of their child’s
    weight status.
    School-based BMI-surveillance data
    can be used to
    ● describe trends in weight status
    over time among populations
    and/or subpopulations in a school,
    school district, state, or nation;
    ● identify demographic or geographic
    subgroups at greatest risk of obesity
    to target prevention and treatment
    programs;
    ● create awareness among school
    and health personnel, community
    members, and policy makers of the
    extent of obesity among the youth
    they serve;
    ● provide an impetus to improve policies,
    practices, and services to prevent
    and treat obesity among youth;
    ● monitor the effects of school-based
    physical activity and nutrition programs
    and policies; and
    ● monitor progress toward achieving
    health objectives (eg, US Healthy
    People 2010 objectives) related to
    childhood obesity.
    Screening
    BMI-screening programs in schools
    are designed to assess the weight status
    of individual students to detect
    those who are at risk for weightrelated
    health problems. Screening
    programs provide parents with personalized
    health information about
    their child. Screening results are sent
    to parents and typically include the
    child’s BMI-for-age percentile; an explanation
    of the results; recommended
    follow-up actions, if any; and tips on
    healthy eating, physical activity, and
    healthy weight management.9,24–27 Results
    from screening programs also
    can be used to develop reports similar
    to those developed by surveillance
    programs.28,29
    Goals of BMI-screening programs in
    schools include
    ● preventing and reducing obesity in
    a population;
    ● correcting misperceptions of parents
    and children about the children’s
    weight;
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    ● motivating parents and their children
    to make healthy and safe lifestyle
    changes;
    ● motivating parents to take children
    at risk to medical care providers for
    further evaluation and, if needed,
    guidance and treatment; and
    ● increasing awareness of school administrators
    and school staff of the
    importance of addressing obesity.
    Schools sometimes include BMI results
    with results from other health
    screening examinations, such as vision
    or hearing tests, in reports to
    parents.30
    CURRENT PRACTICES
    The CDC’s 2006 school health policies
    and programs study found that 22% of
    states required schools or school districts
    to measure or assess students’
    height and weight or body mass, and
    73% of those states required parent
    notification of the results.31 Nationwide,
    40% of schools reported that
    they measure the height and weight or
    body mass of their students.31 The
    study did not determine how frequently
    students are assessed,
    whether BMIs are calculated from the
    height and weight data, or the purpose
    of the data collections.
    At least 13 states have legislation and
    are implementing school-based BMImeasurement
    programs (Arkansas,
    California, Delaware, Florida, Illinois,
    Louisiana, New York, Pennsylvania,
    South Carolina, Tennessee, Texas, Vermont,
    and West Virginia). Arkansas implemented
    a statewide BMI-screening
    and -surveillance program in 2003
    (State of Arkansas, 84th General Assembly,
    regular session, Act 1220 of
    2003, HB 1583). Pennsylvania began to
    phase in a BMI-screening and
    -surveillance program (28 Pennsylvania
    Code §23.7) for all students in
    the 2005–2006 school year (Commonwealth
    of Pennsylvania, Height and
    Weight Measurements, 28 Pennsylvania
    Code §23.21, 2004). In 1995, California
    initiated statewide surveillance of
    student physical fitness levels, which
    includes BMI assessments and tests of
    aerobic capacity, flexibility, and muscle
    strength.32 In Illinois, the Department
    of Public Health is in the process
    of developing a child health examination
    surveillance system. This system
    will aggregate BMI and possibly other
    health information collected during
    students’ school physical examinations
    by their medical care providers
    (Illinois 93rd General Assembly, Public
    Act 93– 0966, SB 2940, 2004).
    CONCERNS
    A number of concerns have been expressed
    about school-based BMIscreening
    programs, including that
    they might intensify the stigmatization
    already experienced by many obese
    youth, increase dissatisfaction with
    body image, and intensify pressures to
    engage in harmful weight-loss practices
    that could lead to eating disorders.
    6–8,10–12,33–36 Another concern is
    that parents might respond inappropriately
    to BMI reports by, for example,
    placing their child on a restrictive and
    potentially harmful diet without seeking
    medical advice.7,8,12,25 Other concerns
    are that these programs might
    be ineffective, waste scarce healthpromotion
    resources, and distract attention
    from other school-based
    obesity-prevention activities such as
    improvements to the school physical
    activity and nutrition environment.37
    More research is needed to assess
    the validity of these concerns. BMIsurveillance
    programs are less controversial,
    because they do not involve
    the communication of sensitive information
    to parents and do not require
    follow-up care.
    RESEARCH ON BMI-MEASUREMENT
    PROGRAMS
    Studies have not yet adequately evaluated
    the utility of school-based BMImeasurement
    programs in preventing
    increases in obesity among youth. A
    few jurisdictions have monitored the
    prevalence of obesity through childhood
    obesity interventions that include
    BMI screening; however, the
    independent effects of the BMIscreening
    program on obesity are not
    clear.9,28,32 Arkansas is evaluating the impact
    of its multicomponent, childhood
    obesity program that includes a statewide
    BMI-screening and -surveillance
    program. The percentage of Arkansas
    students classified as obese was 20.8%
    in 2003–2004, the first year of implementation,
    20.7% in 2004–2005, 20.4% in
    2005–2006 and 20.4% in 2006–2007, and
    20.5% in 2007–2008.38
    A small body of research has addressed
    issues related to schoolbased
    BMI-measurement programs including
    perceptions of weight status,
    parental perceptions of BMI-screening
    programs, and student and parental
    responses to the results. Additional research
    is needed on possible psychosocial
    effects of BMI screening on
    students.
    PERCEPTIONS OF WEIGHT STATUS
    Several studies have found that parents
    and children commonly misclassify
    children’s weight status.29,39–44 A
    study of 742 mothers of adolescents
    found that 35% underestimated their
    child’s weight status and 5% overestimated
    it; 86% of mothers whose child
    had a BMI at 95th percentile did not
    identify their child as overweight.40 A
    study of 2032 high school students
    found that 26% of obese students perceived
    themselves as underweight,
    and another 20% perceived themselves
    as “about the right weight”; only
    6% of normal-weight students perceived
    themselves as overweight.41 The
    evaluation of the Arkansas statewide
    BMI-screening program found that the
    percentage of parents who classified
    their child accurately as overweight or
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    at risk of overweight increased from
    40% at baseline to 53% after the first
    year of screening.29
    PARENTAL PERCEPTIONS OF BMI
    SCREENING IN SCHOOLS
    Five studies included parent interviews
    and found that most parents
    support and respond positively to
    BMI screening in their children’s
    schools.25,29,35,45,46 One of these studies
    analyzed focus-group discussions with
    parents of elementary school children
    in Minnesota. The investigators concluded
    that parents in this study were
    receptive to BMI screening in schools
    provided it is done with care and parents
    are involved in developing the program.
    35 Parents would support programs
    if they receive advanced notice
    about the BMI measurement, have the
    opportunity to decline consent, receive
    assurance that the measurements
    would be collected in a private and respectful
    manner that minimizes
    weight-related teasing, and receive the
    results in a letter mailed to all parents
    that uses a neutral tone and does not
    assign blame.35 A pilot BMI-screening
    program was developed on the basis
    of the findings of these focus groups; 4
    elementary schools were recruited to
    examine parental reaction to BMI measurement.
    45 All 4 schools conducted
    height and weight measurements;
    however, the 2 intervention schools
    mailed BMI results to parents,
    whereas the remaining 2 schools did
    not mail results to the home. A
    follow-up survey found that 78% of parents
    in all 4 schools believed it was
    important for schools to assess and
    mail BMI results to the home as part of
    annual student health-screening reports.
    Parents of girls and older children
    were less likely than parents of
    boys and younger children to want annual
    BMI-screening information.45
    A study conducted in Ohio examined
    parents’ perceptions on the role of elementary
    schools in preventing childhood
    obesity and found that parents
    were least likely to support BMIrelated
    activities. Parents rated the
    importance of 37 actions schools can
    take to address obesity through health
    education, food services, and physical
    education. Using a Likert-type scale
    (eg, not important to very important),
    the lowest-rated actions were collecting
    height and weight measurements
    and informing parents of their child’s
    height and weight.47