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

30341. 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
       STUDENT AND PARENTAL
       RESPONSES TO BMI SCREENINGS
       Arkansas evaluated its statewide program
       for any negative psychosocial
       consequences that may have been experienced
       by the students. After 4
       years of BMI screenings, Arkansas students
       reported no increases in weightrelated
       teasing, no increases in concerns
       about weight, and no increases
       in dieting or using diet pills.48 However,
       obese students were significantly
       more likely to be embarrassed by BMI
       measurement.
       Three school-based screening programs
       that evaluated parental responses
       observed that parents do not
       consistently follow-up with a medical
       care provider after receiving their
       child’s screening results.25,29,49 An evaluation
       of a school-based health “report
       card” revealed that the parents
       who received their child’s BMI results
       were more likely than parents who did
       not receive the results to report that
       they had initiated or intended to initiate
       clinical services, dieting, or physical
       activity as weight control for their
       children. However, 7 of the 19 families
       planning to initiate dieting reported
       that they planned to do so without
       seeking medical counsel despite
       strong recommendations against
       such actions.25 The evaluation of Arkansas’
       statewide screening program
       revealed that parents did not consult
       school nurses about their child’s BMI,
       and most family practitioners and pediatricians
       surveyed reported that
       they were not contacted by a substantial
       number of parents wanting to discuss
       their child’s weight status.29 However,
       parents did not put students on
       diets with a greater frequency than
       they did before the program.48
       RECOMMENDATIONS FROM EXPERT
       ORGANIZATIONS
       The use of BMI measurement for surveillance
       purposes, regardless of setting,
       has been endorsed by the American
       Public Health Association, The
       American Heart Association and the
       IOM.13,50,51 However, views on BMI
       screening vary. The US Preventive Services
       Task Force concluded that insufficient
       evidence exists to recommend
       for or against BMI-screening programs
       for youth in clinical settings as
       a means to prevent adverse health outcomes
       such as adult cardiovascular
       disease risk.52 However, authors of the
       2007 report of an expert committee on
       childhood obesity convened by the
       American Medical Association recommended
       that primary care providers calculate
       and plot BMI at least annually; this
       has been endorsed by 12 organizations.
       53–56 For school-based programs,
       the IOM recommends annual BMI
       screening,13 whereas other organizations
       encourage schools to exercise caution
       before adopting BMI-measurement
       programs.33,50,57
       The American Academy of Pediatrics
       (AAP) developed criteria to guide decisions
       on whether schools should implement
       a screening program for any
       pediatric health problem (Table 1).58
       BMI screening meets some of the criteria:
       obesity is an important and
       highly prevalent condition59,60; BMI
       is an acceptable measure20,22; and
       schools are a logical measurement
       site, because they reach virtually all
       youth.1 However, BMI-screening pro-
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       grams typically do not meet other AAP
       criteria: effective treatments for obesity
       are not available,8,23,61 research
       has not established the effectiveness
       and cost-effectiveness of these programs,
       and communities typically do
       not have resources in place to help individuals
       at risk access treatment.13
       The AAP specifies that schools should
       not implement screening if resources
       for follow-up do not exist.
       GUIDANCE ON MEASURING BMI IN
       SCHOOLS
       Before launching a BMI-measurement
       program for surveillance or screening,
       decision-makers need to consider
       whether the anticipated benefits (eg,
       preventing obesity, correcting misperceptions
       of weight) outweigh the expected
       costs (eg, monetary, psychosocial
       consequences). To minimize
       potential harm and maximize benefits,
       schools should not launch a BMImeasurement
       program unless they
       have established a safe and supportive
       environment for students of all body
       sizes; are implementing comprehensive
       strategies to address obesity; and
       have put in place safeguards that address
       the concerns raised about such
       programs.
       The following are some key characteristics
       of a safe and supportive environment
       for students of all body sizes26:
       ● There is a universal bullyingprevention
       program that addresses
       weight discrimination.
       ● Curricula foster acceptance of
       healthy weight by countering social
       pressures for excessive thinness.
       ● Teachers, school counselors, school
       nurses, coaches, and other staff receive
       the professional development
       and resources they need to provide
       useful guidance to students with
       weight-related concerns.
       If schools raise awareness about obesity
       through a BMI-measurement program,
       they need to have in place an
       environment that helps students make
       healthy dietary and physical activity
       choices. For example, Arkansas required
       all elementary schools to remove
       vending machines from schools
       concurrent with implementing the
       statewide BMI-measurement program.62
       California’s physical performance
       tests influenced the adoption of statewide,
       grade-specific physical education
       content standards.63 The CDC has
       identified 10 comprehensive strategies
       that schools can implement to
       prevent obesity by promoting physical
       activity and healthy eating (www.cdc.
       gov/healthyyouth/keystrategies).5
       To ensure respect for student privacy
       and confidentiality, protect students
       from potential harm, and increase
       the likelihood of a positive impact
       on promoting a healthy weight, all BMImeasurement
       programs should adhere
       to the following safeguards.6,26
       ● Introduce the program to school
       staff and community members and
       obtain parental consent.
       ● Train staff in administering the program
       (ideally, implementation will
       be led by a highly qualified staff
       member such as a school nurse).
       ● Establish safeguards to protect student
       privacy.
       ● Obtain and use accurate equipment.
       ● Accurately calculate and interpret
       the data.
       ● Develop efficient data-collection
       procedures.
       ● Avoid using BMI results to evaluate
       student or teacher performance.
       ● Evaluate the program regularly for
       its intended outcomes and unintended
       consequences.
       Those who implement BMI-screening
       programs should ensure that all parents
       receive a clear and respectful explanation
       of the results and appropriate
       follow-up actions, and that
       resources are available for safe and
       effective follow-up. Greater detail of
       these safeguards are described in the
       longer version of this article in the December
       2007 issue of the Journal of
       School Health.64
       TABLE 1 AAP Criteria for a Successful Screening Program in Schools58
       Aspect Criteria for a Successful Screening Program in Schools
       Disease Undetected cases must be common or new cases must occur frequently, and the disease must be associated with adverse
       consequences.
       Treatment Effective treatment must be available, and early intervention must be beneficial.
       Screening test The test should be sensitive, specific, and reliable.
       Screener The screener must be well trained.
       Target population Screening should focus on groups with high prevalence of the condition/disease in question or in which early intervention
       will be most beneficial.
       Referral and treatment Those with a positive screening test result must receive a more definitive evaluation and, if indicated, appropriate treatment.
       Cost/benefit ratio The benefit should outweigh the expenses (ie, costs of conducting the screening and any physical or psychosocial effects on
       the individual being screened).
       Site The site should be appropriate for conducting the screening and communicating the results.
       Program maintenance The program should be reviewed for its value and effectiveness.
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       Research is needed to address outstanding
       issues regarding schoolbased
       BMI-surveillance and -screening
       programs, including
       ● program impact on preventing and
       reducing obesity;
       ● the types of follow-up actions taken
       by parents and students;
       ● the programs’ intended and unintended
       physical, social, and psychological
       effects;
       ● student perceptions of and attitudes
       toward height and weight
       measurement in schools;
       ● the role and capacity of the school or
       school district nurse to implement
       and manage the BMI-measurement
       program;
       ● the effects of BMI-measurement
       programs on school-based efforts
       to promote nutrition and physical
       activity and link parents with medical
       services in the community;
       ● the effectiveness of treatment for
       youth identified as obese, overweight,
       or underweight;
       ● cost/benefit analyses of these programs
       compared with alternative
       strategies;
       ● relative efficiency of using schools
       as a BMI-measurement site; and
       ● effectiveness of different methods
       for communicating BMI results and
       related risk information to parents
       and youth.
       There is a need for researchers in academia,
       government, and scientific organizations
       to develop a research agenda
       around school-based BMI-measurement
       programs, document the impact of data
       collection on obesity-prevention policies,
       study the data currently being collected,
       and define safe, effective, and accessible
       follow-up services.
       CONCLUSIONS
       School-based BMI-surveillance programs
       are less controversial than
       screening programs, but they still must
       adhere to the safeguards identified. Surveillance
       programs can provide valuable
       prevalence and trend data; samples
       should be selected carefully to ensure
       representativeness and to minimize program
       costs.
       More research needs to be conducted to
       evaluate the impact of BMI-screening
       programs on weight-related behaviors
       and outcomes. Legitimate concerns
       have been raised about the potential
       harm that might be caused by BMIscreening
       programs; more research is
       needed to assess whether these harms
       occur. BMI-screening programs do not
       yet meet AAP criteria for a successful
       school screening program. The CDC encourages
       additional research and evaluation
       on school-based BMI-screening
       programs. Before initiating BMImeasurement
       programs, decisionmakers
       should consider the benefits
       and disadvantages of these programs in
       relation to the needs of their jurisdiction
       and resources available.
       ACKNOWLEDGMENTS
       We thank Laura Dobbs (past president,
       Georgia Parent Teacher Association),
       Joyce Epstein, PhD (director, Center on
       School, Family, and Community Partnerships),
       Suzanne Bennette Johnson,
       PhD (professor and chair, Department
       of Medical Humanities and Social Sciences,
       Florida State University College
       of Medicine), Martha Kubik, PhD (associate
       professor, School of Nursing, University
       of Minnesota), Maryann Mason,
       PhD (associate director, Center for
       Obesity Management and Prevention,
       Mary Ann and J. Milburn Smith Child
       Health Research Program, Children’s
       Memorial Research Center), Mary Pat
       McCartney, PhD (former elementary
       vice-president, American School Counselor
       Association), Martha Phillips,
       PhD (assistant professor, Department
       of Psychiatry and Epidemiology, University
       of Arkansas for Medical Science),
       Shirley Shantz, EdD, ARNP
       (nursing projects director, National
       Association of School Nurses), Howard
       Taras, MD (professor, School of Medicine,
       University of California San Diego),
       and Gail Woodward-Lopez, MPH,
       RD (associate director, Center for
       Weight and Health, University of California
       Berkeley), for their review and
       expertise.
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