BMI Measurement in Schools


CONTRIBUTORS: Allison J. Nihiser, MPH,a Sarah M. Lee,PhD,a Howell Wechsler, EdD,a Mary McKenna, PhD,b EricaOdom, MPH,a Chris Reinold, PhD, RD,c Diane Thompson,MPH, RD,c and Larry Grummer-Strawn, PhDcDivisions of aAdolescent and School Health and cNutrition,Physical Activity, and Obesity, Centers for Disease Control andPrevention, Atlanta, Georgia; and bDepartment of Kinesiology,University of New Brunswick, Fredericton, New Brunswick,CanadaKEY WORDSbody mass index, obesity, growth and development, schoolhealth services, child, adolescentABBREVIATIONSCDC—Centers for Disease Control and PreventionIOM—Institute of MedicineAAP—American Academy of PediatricsThis article is based on a longer article first published in theJournal 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 theauthors and do not necessarily represent the official position ofthe Centers for Disease Control and for publication Apr 29, 2009Address correspondence to Allison J. Nihiser, MPH, Centers forDisease Control and Prevention, Division of Adolescent andSchool Health, 4770 Buford Hwy NE, Mailstop K-12, Atlanta, GA

E-mail: anihiser@cdc.govPEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, 1098-4275).Copyright © 2009 by the American Academy of PediatricsFINANCIAL DISCLOSURE: The authors have indicated they haveno financial relationships relevant to this article to disclose.SUPPLEMENT ARTICLEDownloaded from by guesPt EoDnI AMTRaIyC S3V0o, l2u0m2e0124, Supplement 1, September 2009 S89Obesity among youth has become 1 ofthe most critical public health problemsin the United States. Schools canplay an important role in preventingobesity because 95% of young peopleare enrolled in schools,1 andschools have historically promotedphysical activity and healthy eating. Researchhas shown that well-designed,well-implemented school-based programscan effectively promote thesebehaviors,2–4 and the Centers for DiseaseControl and Prevention (CDC) hasidentified strategies that schools canuse to prevent obesity.5Measuring the BMI of students inschools is an approach to addressingobesity that is attracting attentionacross the nation from researchers,school officials, legislators, and themedia.6–12 Because little research hasbeen conducted on the impact of thisapproach, it is not included in theCDC’s recommended strategies. However,some states, cities, and communitieshave established school-basedBMI-measurement programs in recentyears, and many others are consideringthe merits of initiating such programs.In 2005, the Institute of Medicine (IOM)called on the federal government to developguidance for BMI-measurementprograms in schools.13 The CDC conductedan extensive search for scientificstudies that evaluated school-basedBMI-measurement programs; collectedrelated position statementspublished by expert organizationsfrom public health, medicine, and education;and reviewed sources to identifystate legislation on these programsincluding policy-trackingservices, state general assembly legislativedatabases, and staff in state educationor health departments.14–18 Anexpert panel, convened by the CDC in2005, provided input on an earlier versionof this article. The panel comprisedexperts in public health, education,school counseling, schoolmedical care, and parenting. This articlepresents an overview of the CDC’sguidance on this topic; it describes thepurposes of BMI-measurement programs,examines current practices,reviews existing research, summarizesexpert recommendations, identifiesresearch gaps, and provides guidanceand safeguards for implementingBMI-measurement programs.PURPOSES OF COLLECTING BMIDATABMI is the ratio of an individual’sweight to height squared (kg/m2) andis used to estimate a person’s risk ofweight-related health problems. It isoften used to assess weight status, becauseit is relatively easy to measureand correlates with body fat.19–23 AfterBMI is calculated for a child or adolescent,it is plotted by age on a genderspecificgrowth chart (see for the CDC’s BMIfor-age growth charts for girls andboys aged 2–20 years). BMI measurementin schools may be conducted forsurveillance and screening purposes.SurveillanceSurveillance refers to the systematiccollection, analysis, and interpretationof data from a census or representativesample (ie, a sample that has beenscientifically selected to represent aspecified population). Typically, thedata are collected anonymously. Thepurpose of BMI surveillance in schoolsis to identify the percentages of studentsin the population who are obese,overweight, normal weight, and underweight;surveillance does not involveinforming parents of their child’sweight status.School-based BMI-surveillance datacan be used to● describe trends in weight statusover time among populationsand/or subpopulations in a school,school district, state, or nation;● identify demographic or geographicsubgroups at greatest risk of obesityto target prevention and treatmentprograms;● create awareness among schooland health personnel, communitymembers, and policy makers of theextent of obesity among the youththey serve;● provide an impetus to improve policies,practices, and services to preventand treat obesity among youth;● monitor the effects of school-basedphysical activity and nutrition programsand policies; and● monitor progress toward achievinghealth objectives (eg, US HealthyPeople 2010 objectives) related tochildhood obesity.ScreeningBMI-screening programs in schoolsare designed to assess the weight statusof individual students to detectthose who are at risk for weightrelatedhealth problems. Screeningprograms provide parents with personalizedhealth information abouttheir child. Screening results are sentto parents and typically include thechild’s BMI-for-age percentile; an explanationof the results; recommendedfollow-up actions, if any; and tips onhealthy eating, physical activity, andhealthy weight management.9,24–27 Resultsfrom screening programs alsocan be used to develop reports similarto those developed by surveillanceprograms.28,29Goals of BMI-screening programs inschools include● preventing and reducing obesity ina population;● correcting misperceptions of parentsand children about the children’sweight;S90 NIHISER et al Downloaded from by guest on May 30, 2020● motivating parents and their childrento make healthy and safe lifestylechanges;● motivating parents to take childrenat risk to medical care providers forfurther evaluation and, if needed,guidance and treatment; and● increasing awareness of school administratorsand school staff of theimportance of addressing obesity.Schools sometimes include BMI resultswith results from other healthscreening examinations, such as visionor hearing tests, in reports toparents.30CURRENT PRACTICESThe CDC’s 2006 school health policiesand programs study found that 22% ofstates required schools or school districtsto measure or assess students’height and weight or body mass, and73% of those states required parentnotification of the results.31 Nationwide,40% of schools reported thatthey measure the height and weight orbody mass of their students.31 Thestudy did not determine how frequentlystudents are assessed,whether BMIs are calculated from theheight and weight data, or the purposeof the data collections.At least 13 states have legislation andare implementing school-based BMImeasurementprograms (Arkansas,California, Delaware, Florida, Illinois,Louisiana, New York, Pennsylvania,South Carolina, Tennessee, Texas, Vermont,and West Virginia). Arkansas implementeda statewide BMI-screeningand -surveillance program in 2003(State of Arkansas, 84th General Assembly,regular session, Act 1220 of2003, HB 1583). Pennsylvania began tophase in a BMI-screening and-surveillance program (28 PennsylvaniaCode §23.7) for all students inthe 2005–2006 school year (Commonwealthof Pennsylvania, Height andWeight Measurements, 28 PennsylvaniaCode §23.21, 2004). In 1995, Californiainitiated statewide surveillance ofstudent physical fitness levels, whichincludes BMI assessments and tests ofaerobic capacity, flexibility, and musclestrength.32 In Illinois, the Departmentof Public Health is in the processof developing a child health examinationsurveillance system. This systemwill aggregate BMI and possibly otherhealth information collected duringstudents’ school physical examinationsby their medical care providers(Illinois 93rd General Assembly, PublicAct 93– 0966, SB 2940, 2004).CONCERNSA number of concerns have been expressedabout school-based BMIscreeningprograms, including thatthey might intensify the stigmatizationalready experienced by many obeseyouth, increase dissatisfaction withbody image, and intensify pressures toengage in harmful weight-loss practicesthat could lead to eating disorders.6–8,10–12,33–36 Another concern isthat parents might respond inappropriatelyto BMI reports by, for example,placing their child on a restrictive andpotentially harmful diet without seekingmedical advice.7,8,12,25 Other concernsare that these programs mightbe ineffective, waste scarce healthpromotionresources, and distract attentionfrom other school-basedobesity-prevention activities such asimprovements to the school physicalactivity and nutrition environment.37More research is needed to assessthe validity of these concerns. BMIsurveillanceprograms are less controversial,because they do not involvethe communication of sensitive informationto parents and do not requirefollow-up care.RESEARCH ON BMI-MEASUREMENTPROGRAMSStudies have not yet adequately evaluatedthe utility of school-based BMImeasurementprograms in preventingincreases in obesity among youth. Afew jurisdictions have monitored theprevalence of obesity through childhoodobesity interventions that includeBMI screening; however, theindependent effects of the BMIscreeningprogram on obesity are notclear.9,28,32 Arkansas is evaluating the impactof its multicomponent, childhoodobesity program that includes a statewideBMI-screening and -surveillanceprogram. The percentage of Arkansasstudents classified as obese was 20.8%in 2003–2004, the first year of implementation,20.7% in 2004–2005, 20.4% in2005–2006 and 20.4% in 2006–2007, and20.5% in 2007–2008.38A small body of research has addressedissues related to schoolbasedBMI-measurement programs includingperceptions of weight status,parental perceptions of BMI-screeningprograms, and student and parentalresponses to the results. Additional researchis needed on possible psychosocialeffects of BMI screening onstudents.PERCEPTIONS OF WEIGHT STATUSSeveral studies have found that parentsand children commonly misclassifychildren’s weight status.29,39–44 Astudy of 742 mothers of adolescentsfound that 35% underestimated theirchild’s weight status and 5% overestimatedit; 86% of mothers whose childhad a BMI at 95th percentile did notidentify their child as overweight.40 Astudy of 2032 high school studentsfound that 26% of obese students perceivedthemselves as underweight,and another 20% perceived themselvesas “about the right weight”; only6% of normal-weight students perceivedthemselves as overweight.41 Theevaluation of the Arkansas statewideBMI-screening program found that thepercentage of parents who classifiedtheir child accurately as overweight orSUPPLEMENT ARTICLEDownloaded from by guesPt EoDnI AMTRaIyC S3V0o, l2u0m2e0124, Supplement 1, September 2009 S91at risk of overweight increased from40% at baseline to 53% after the firstyear of screening.29PARENTAL PERCEPTIONS OF BMISCREENING IN SCHOOLSFive studies included parent interviewsand found that most parentssupport and respond positively toBMI screening in their children’sschools.25,29,35,45,46 One of these studiesanalyzed focus-group discussions withparents of elementary school childrenin Minnesota. The investigators concludedthat parents in this study werereceptive to BMI screening in schoolsprovided it is done with care and parentsare involved in developing the program.35 Parents would support programsif they receive advanced noticeabout the BMI measurement, have theopportunity to decline consent, receiveassurance that the measurementswould be collected in a private and respectfulmanner that minimizesweight-related teasing, and receive theresults in a letter mailed to all parentsthat uses a neutral tone and does notassign blame.35 A pilot BMI-screeningprogram was developed on the basisof the findings of these focus groups; 4elementary schools were recruited toexamine parental reaction to BMI measurement.45 All 4 schools conductedheight and weight measurements;however, the 2 intervention schoolsmailed BMI results to parents,whereas the remaining 2 schools didnot mail results to the home. Afollow-up survey found that 78% of parentsin all 4 schools believed it wasimportant for schools to assess andmail BMI results to the home as part ofannual student health-screening reports.Parents of girls and older childrenwere less likely than parents ofboys and younger children to want annualBMI-screening information.45A study conducted in Ohio examinedparents’ perceptions on the role of elementaryschools in preventing childhoodobesity and found that parentswere least likely to support BMIrelatedactivities. Parents rated theimportance of 37 actions schools cantake to address obesity through healtheducation, food services, and physicaleducation. Using a Likert-type scale(eg, not important to very important),the lowest-rated actions were collectingheight and weight measurementsand informing parents of their child’sheight and weight.47STUDENT AND PARENTALRESPONSES TO BMI SCREENINGSArkansas evaluated its statewide programfor any negative psychosocialconsequences that may have been experiencedby the students. After 4years of BMI screenings, Arkansas studentsreported no increases in weightrelatedteasing, no increases in concernsabout weight, and no increasesin dieting or using diet pills.48 However,obese students were significantlymore likely to be embarrassed by BMImeasurement.Three school-based screening programsthat evaluated parental responsesobserved that parents do notconsistently follow-up with a medicalcare provider after receiving theirchild’s screening results.25,29,49 An evaluationof a school-based health “reportcard” revealed that the parentswho received their child’s BMI resultswere more likely than parents who didnot receive the results to report thatthey had initiated or intended to initiateclinical services, dieting, or physicalactivity as weight control for theirchildren. However, 7 of the 19 familiesplanning to initiate dieting reportedthat they planned to do so withoutseeking medical counsel despitestrong recommendations againstsuch actions.25 The evaluation of Arkansas’statewide screening programrevealed that parents did not consultschool nurses about their child’s BMI,and most family practitioners and pediatricianssurveyed reported thatthey were not contacted by a substantialnumber of parents wanting to discusstheir child’s weight status.29 However,parents did not put students ondiets with a greater frequency thanthey did before the program.48RECOMMENDATIONS FROM EXPERTORGANIZATIONSThe use of BMI measurement for surveillancepurposes, regardless of setting,has been endorsed by the AmericanPublic Health Association, TheAmerican Heart Association and theIOM.13,50,51 However, views on BMIscreening vary. The US Preventive ServicesTask Force concluded that insufficientevidence exists to recommendfor or against BMI-screening programsfor youth in clinical settings asa means to prevent adverse health outcomessuch as adult cardiovasculardisease risk.52 However, authors of the2007 report of an expert committee onchildhood obesity convened by theAmerican Medical Association recommendedthat primary care providers calculateand plot BMI at least annually; thishas been endorsed by 12 organizations.53–56 For school-based programs,the IOM recommends annual BMIscreening,13 whereas other organizationsencourage schools to exercise cautionbefore adopting BMI-measurementprograms.33,50,57The American Academy of Pediatrics(AAP) developed criteria to guide decisionson whether schools should implementa screening program for anypediatric health problem (Table 1).58BMI screening meets some of the criteria:obesity is an important andhighly prevalent condition59,60; BMIis an acceptable measure20,22; andschools are a logical measurementsite, because they reach virtually allyouth.1 However, BMI-screening pro-S92 NIHISER et al Downloaded from by guest on May 30, 2020grams typically do not meet other AAPcriteria: effective treatments for obesityare not available,8,23,61 researchhas not established the effectivenessand cost-effectiveness of these programs,and communities typically donot have resources in place to help individualsat risk access treatment.13The AAP specifies that schools shouldnot implement screening if resourcesfor follow-up do not exist.GUIDANCE ON MEASURING BMI INSCHOOLSBefore launching a BMI-measurementprogram for surveillance or screening,decision-makers need to considerwhether the anticipated benefits (eg,preventing obesity, correcting misperceptionsof weight) outweigh the expectedcosts (eg, monetary, psychosocialconsequences). To minimizepotential harm and maximize benefits,schools should not launch a BMImeasurementprogram unless theyhave established a safe and supportiveenvironment for students of all bodysizes; are implementing comprehensivestrategies to address obesity; andhave put in place safeguards that addressthe concerns raised about suchprograms.The following are some key characteristicsof a safe and supportive environmentfor students of all body sizes26:● There is a universal bullyingpreventionprogram that addressesweight discrimination.● Curricula foster acceptance ofhealthy weight by countering socialpressures for excessive thinness.● Teachers, school counselors, schoolnurses, coaches, and other staff receivethe professional developmentand resources they need to provideuseful guidance to students withweight-related concerns.If schools raise awareness about obesitythrough a BMI-measurement program,they need to have in place anenvironment that helps students makehealthy dietary and physical activitychoices. For example, Arkansas requiredall elementary schools to removevending machines from schoolsconcurrent with implementing thestatewide BMI-measurement program.62California’s physical performancetests influenced the adoption of statewide,grade-specific physical educationcontent standards.63 The CDC hasidentified 10 comprehensive strategiesthat schools can implement toprevent obesity by promoting physicalactivity and healthy eating ( ensure respect for student privacyand confidentiality, protect studentsfrom potential harm, and increasethe likelihood of a positive impacton promoting a healthy weight, all BMImeasurementprograms should adhereto the following safeguards.6,26● Introduce the program to schoolstaff and community members andobtain parental consent.● Train staff in administering the program(ideally, implementation willbe led by a highly qualified staffmember such as a school nurse).● Establish safeguards to protect studentprivacy.● Obtain and use accurate equipment.● Accurately calculate and interpretthe data.● Develop efficient data-collectionprocedures.● Avoid using BMI results to evaluatestudent or teacher performance.● Evaluate the program regularly forits intended outcomes and unintendedconsequences.Those who implement BMI-screeningprograms should ensure that all parentsreceive a clear and respectful explanationof the results and appropriatefollow-up actions, and thatresources are available for safe andeffective follow-up. Greater detail ofthese safeguards are described in thelonger version of this article in the December2007 issue of the Journal ofSchool Health.64TABLE 1 AAP Criteria for a Successful Screening Program in Schools58Aspect Criteria for a Successful Screening Program in SchoolsDisease Undetected cases must be common or new cases must occur frequently, and the disease must be associated with adverseconsequences.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 interventionwill 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 onthe 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.SUPPLEMENT ARTICLEDownloaded from by guesPt EoDnI AMTRaIyC S3V0o, l2u0m2e0124, Supplement 1, September 2009 S93Research is needed to address outstandingissues regarding schoolbasedBMI-surveillance and -screeningprograms, including● program impact on preventing andreducing obesity;● the types of follow-up actions takenby parents and students;● the programs’ intended and unintendedphysical, social, and psychologicaleffects;● student perceptions of and attitudestoward height and weightmeasurement in schools;● the role and capacity of the school orschool district nurse to implementand manage the BMI-measurementprogram;● the effects of BMI-measurementprograms on school-based effortsto promote nutrition and physicalactivity and link parents with medicalservices in the community;● the effectiveness of treatment foryouth identified as obese, overweight,or underweight;● cost/benefit analyses of these programscompared with alternativestrategies;● relative efficiency of using schoolsas a BMI-measurement site; and● effectiveness of different methodsfor communicating BMI results andrelated risk information to parentsand youth.There is a need for researchers in academia,government, and scientific organizationsto develop a research agendaaround school-based BMI-measurementprograms, document the impact of datacollection on obesity-prevention policies,study the data currently being collected,and define safe, effective, and accessiblefollow-up services.CONCLUSIONSSchool-based BMI-surveillance programsare less controversial thanscreening programs, but they still mustadhere to the safeguards identified. Surveillanceprograms can provide valuableprevalence and trend data; samplesshould be selected carefully to ensurerepresentativeness and to minimize programcosts.More research needs to be conducted toevaluate the impact of BMI-screeningprograms on weight-related behaviorsand outcomes. Legitimate concernshave been raised about the potentialharm that might be caused by BMIscreeningprograms; more research isneeded to assess whether these harmsoccur. BMI-screening programs do notyet meet AAP criteria for a successfulschool screening program. The CDC encouragesadditional research and evaluationon school-based BMI-screeningprograms. Before initiating BMImeasurementprograms, decisionmakersshould consider the benefitsand disadvantages of these programs inrelation to the needs of their jurisdictionand resources available.ACKNOWLEDGMENTSWe thank Laura Dobbs (past president,Georgia Parent Teacher Association),Joyce Epstein, PhD (director, Center onSchool, Family, and Community Partnerships),Suzanne Bennette Johnson,PhD (professor and chair, Departmentof Medical Humanities and Social Sciences,Florida State University Collegeof Medicine), Martha Kubik, PhD (associateprofessor, School of Nursing, Universityof Minnesota), Maryann Mason,PhD (associate director, Center forObesity Management and Prevention,Mary Ann and J. Milburn Smith ChildHealth Research Program, Children’sMemorial Research Center), Mary PatMcCartney, PhD (former elementaryvice-president, American School CounselorAssociation), Martha Phillips,PhD (assistant professor, Departmentof Psychiatry and Epidemiology, Universityof Arkansas for Medical Science),Shirley Shantz, EdD, ARNP(nursing projects director, NationalAssociation of School Nurses), HowardTaras, MD (professor, School of Medicine,University of California San Diego),and Gail Woodward-Lopez, MPH,RD (associate director, Center forWeight and Health, University of CaliforniaBerkeley), for their review andexpertise.REFERENCES
US Department of Commerce, Census Bureau. Historical statistics of the United States, colonialtimes to 1970. Percent of the population 3 to 34 years old enrolled in school, by race/ethnicity, sexand age: Selected years, 1980 –2003. Available at: Accessed May 8, 2009
Centers for Disease Control and Prevention. Guidelines for school health programs to promotelifelong healthy eating. MMWR Recomm Rep. 1996;45(RR-9):1– 41
Centers for Disease Control and Prevention. Guidelines for school and community programs topromote lifelong physical activity among young people. MMWR Recomm Rep. 1997;46(RR-6):1–36
Gortmaker S, Peterson K, Wiecha J, et al. Reducing obesity via a school-based interdisciplinaryintervention among youth: Planet Health. Arch Pediatr Adolesc Med. 1999;153(4):409–418
Wechsler H, McKenna ML, Lee SM, Dietz WH. The role of schools in preventing childhood obesity.State Educ Stand. 2004;5(2):4 –12

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