www.jped.com.br
ORIGINAL
ARTICLE
Physical
self-efficacy
is
associated
to
body
mass
index
in
schoolchildren
夽
,
夽夽
Alicia
Carissimi
a,b,∗,
Ana
Adan
c,d,
Lorenzo
Tonetti
e,
Marco
Fabbri
f,
Maria
Paz
Hidalgo
a,b,g,
Rosa
Levandovski
a,b,
Vincenzo
Natale
e,
Monica
Martoni
haUniversidadeFederaldoRioGrandedoSul(UFRGS),HospitaldeClínicasdePortoAlegre(HCPA),LaboratóriodeCronobiologiae
Sono,PortoAlegre,RS,Brazil
bUniversidadeFederaldoRioGrandedoSul(UFRGS),ProgramadePós-Graduac¸ãoemPsiquiatriaeCiênciasdoComportamento,
PortoAlegre,RS,Brazil
cUniversitatdeBarcelona,FacultaddePsicología,DepartamentodePsiquiatríayPsicobiologíaClínica,Barcelona,Spain dUniversitatdeBarcelona,InstitutdeRecercaenCervell,CognicióiConducta(IR3C),Barcelona,Spain
eUniversitàdiBologna,DipartimentodiPsicologia,Bologna,Italy
fSecondaUniversitàdegliStudidiNapoli,DipartimentodiPsicologia,Caserta,Italy
gUniversidadeFederaldoRioGrandedoSul(UFRGS),FaculdadedeMedicina,DepartamentodePsiquiatriaeMedicinaLegal,
PortoAlegre,RS,Brazil
hUniversitàdiBologna,DipartimentodiMedicinaSpecialistica,DiagnosticaeSperimentale,Bologna,Italy
Received9October2015;accepted6April2016 Availableonline3October2016
KEYWORDS
Obesity; Overweight; Childhood;
Physicalself-efficacy; PerceivedPhysical AbilityScalefor Children
Abstract
Objective: The present study aimed to investigate the relationship between physical
self-efficacyandbodymassindexinalargesampleofschoolchildren.
Methods: ThePerceivedPhysicalAbilityScaleforChildrenwasadministeredto1560children
(50.4%boys;8---12years)fromthreedifferentcountries.Weightandheightwerealsorecorded
toobtainthebodymassindex.
Results: Inagreementwiththeliterature,theboysreportedgreaterperceivedphysical
self-efficacythangirls.Moreover,thenumberofboyswhoareobeseisdoublethatofgirls,while
thenumberofboyswhoareunderweightishalfthatfound ingirls.Inthelinearregression
model,theincrease inbodymassindexwas negativelyrelatedtothephysicalself-efficacy
score,differentlyforboysandgirls.Furthermore,ageandnationalityalsowerepredictorsof
lowphysicalself-efficacyonlyforgirls.
夽
Pleasecitethisarticleas:CarissimiA,AdanA,TonettiL,FabbriM,HidalgoMP,LevandovskiR,etal.Physicalself-efficacyisassociated tobodymassindexinschoolchildren.JPediatr(RioJ).2017;93:64---9.
夽夽
StudyconductedatUniversityofBologna,Bologna,Italy;HospitaldeClínicasdePortoAlegre(HCPA),UniversidadeFederaldoRio GrandedoSul(UFRGS),PortoAlegre,RS,Brazil;andUniversityofBarcelona,Barcelona,Spain.
∗Correspondingauthor.
E-mail:alicia.ufrgs@gmail.com(A.Carissimi).
http://dx.doi.org/10.1016/j.jped.2016.04.011
Conclusion: Theresultsofthisstudyreinforcetheimportanceofpsychologicalaspectof
obe-sity,astheperceivedphysicalself-efficacyandbodymassindexwerenegativelyassociatedin
asampleofschoolchildrenforboysandgirls.
©2016SociedadeBrasileiradePediatria.PublishedbyElsevierEditoraLtda.Thisisanopen
accessarticleundertheCCBY-NC-NDlicense(http://creativecommons.org/licenses/by-nc-nd/
4.0/).
PALAVRAS-CHAVE
Obesidade; Sobrepeso; Infância;
Autoeficáciafísica; EscaladeCapacidade FísicaPercebidapara Crianc¸as
Autoeficáciafísicaassociadaaoíndicedemassacorporalemcrianc¸asemidade
escolar
Resumo
Objetivo: Esteestudovisouinvestigararelac¸ãoentreaautoeficáciafísicaeoíndicedemassa
corporalemumagrandeamostradecrianc¸asemidadeescolar.
Métodos: A Escala de Capacidade Física Percebida para Crianc¸as foi administrada a 1560
crianc¸as(50,4%meninos;8-12anos)detrêspaísesdiferentes.Opesoeaalturatambémforam
registradosparaobteroíndicedemassacorporal.
Resultados: Deacordocomaliteratura,osmeninosrelatarammaiorautoeficáciafísica
perce-bida queas meninas. Além disso, o número de meninos obesosé o dobrodo de meninas,
ao passoqueonúmerodemeninosabaixodopesoémetadedodemeninas. Nomodelode
regressão linear,o aumentono índice de massacorporal foi negativamente relacionadoao
escoredeautoeficáciafísica,diferentementeemmeninosemeninas.Alémdisso,aidadeea
nacionalidadetambémforampreditorasdeautoeficáciafísicabaixaapenasparameninas.
Conclusão: Os resultados deste estudo reforc¸am a importância do aspecto psicológico da
obesidade,uma vezqueaautoeficáciafísica percebidaeoíndice demassacorporal foram
negativamenteassociadosemumaamostradecrianc¸asemidadeescolarparameninose
meni-nas.
©2016SociedadeBrasileiradePediatria.PublicadoporElsevierEditoraLtda.Este ´eumartigo
OpenAccesssobumalicenc¸aCCBY-NC-ND(http://creativecommons.org/licenses/by-nc-nd/4.
0/).
Introduction
Thehealthbenefitsofregularphysicalactivityforchildren arewellknown.1Togainabetterunderstandingofphysical activitybehavior inchildren, therehas beenan increased focus on determining the relationship between physical activityandpsychosocialcorrelates.2,3Self-efficacy,defined aspeople’s beliefs about their capacity or ability to per-formacertainactionrequiredtoachieveresultsinaspecific situation,4isavariablethatisconsideredtobeassociated withphysicalactivityinadolescents,whichcanbean impor-tantmediatorin providingmore effectiveparticipationin theseactivities.5---7
A recent study on 281 children (116 boys and 165 girls) showed that those who have high physical self-efficacy scores participated in significantly more physical activitycomparedtotheir lowphysical self-efficacyscore counterparts.8 Girls are generally less active and report lowerperceivedphysicalability,aswellashigherperceived body fat and greater body dissatisfaction than boys in a school setting.1,2,6,9,10 Thus, the perceived competence for physical activity seems to be sex-related, due to the fact that boys are more physically active, and per-ceive greater strength and sporting competence than girls.6,11,12
Inadditiontogender,ageisafactorthatmayinfluence physicalself-efficacy,mostevidentlyduringadolescence,6,7 given that physical self-efficacy tends to decrease with increaseofbiologicalage.Anotherfactor,whichcorrelates withself-efficacy, is the body mass index(BMI), an index
ofweight-for-heightthatisusedtoclassifyoverweightand obesity.Changesin perceived physicalabilities9,10,13,14 are influencedbyexcessofweight,relatedtoalowperception of competenceand motivation to performphysical activ-ity,impactingonphysicalactivityparticipationandphysical appearance.15 In fact, higher BMI has been associated to lowerlevelsofself-efficacyfor physicalactivity,including weightstatuspredictedbyphysicalself-efficacyandhealthy eating.16Indeed,olderchildrenandthosewithahigherBMI performlessphysical activity.12 Based onthis evidence,a significant relationship between physical self-efficacyand BMIwasexpectedtobefound.
As demonstratedintheliterature,gender is relatedto BMI, and boys tend to have higher BMI, thus this effect was expected. Therefore, the relationship was explored between physical self-efficacy and BMI in a large sample ofschoolchildren,controllingforconfoundingvariablesthat caninfluencephysicalself-efficacy,suchasage,gender,and nationality.Threecountrieswherethereisaconcernwith theincreased prevalence of overweight andobesity were selected:Italy,17 Spain,18andBrazil.19
Methods
Sample
Spanish (10.54±1.02 years) participants. Students were enrolledbetweenJanuaryandOctober2013onthe condi-tionthatparentssignedtheinformedconsentform.
Measuresandprocedure
Thisstudy presentsdatafromatranscultural projectthat aimstoinvestigatefactors linkedtoenergygainand eat-inghabits,considering theinfluence ofthe rhythmicityof behaviorfromachronobiologicalpointofview.Duringthe schoolyear,studentswereinvitedtoanswerasetof ques-tionnairesaimedatgatheringdataontimingoffoodintake, sleephabits,andphysicalactivity.Duringschoolhours,two membersoftheresearchgroupadministeredquestionnaires inthepresenceoftheteacher.Theteamwenttotheschools at a prearranged time andstudents completed the ques-tionnaires in about 30min. The ethics committee of the universitiesinvolvedintheprojectapprovedthisstudy.
The present study focuses onthe data regarding phys-icalself-efficacy measuredthroughthePerceivedPhysical AbilityScaleforChildren(PPASC)20 inrelationtoage, gen-der,nationality,andBMI.ParticipantscompletedthePPASC, whichconsistsofsixitems:(1)run,rangingfrom1(‘‘Irun veryslowly’’) to4 (‘‘I runvery fast’’);(2) exercise, ran-gingfrom1(‘‘Iamabletodoonlyveryeasyexercises’’)to 4(‘‘Iamabletodoverydifficultexercises’’);(3)muscles, rangingfrom1(‘‘Mymusclesareveryweak’’)to4(‘‘My mus-clesareverystrong’’);(4)move,rangingfrom1(‘‘Imove veryslowly’’)to4 (‘‘Imove veryrapidly’’);(5)sure, ran-gingfrom1(‘‘IfeelveryinsecurewhenImove’’)to4(‘‘I feelverysurewhenImove’’);(6)tired,rangingfrom1(‘‘I feelverytired whenImove’’)to4(‘‘Idon’t feeltiredat allwhenImove’’).Thetotaltestscorecanrangefrom6to 24,andhighscoresindicatethegreatestperceivedphysical self-efficacy.The PPASC assess individuals’ perceptionsof physicalabilitiessuchasstrength,speed,andcoordinative abilities.20 Studieshave foundthatthePPASCis areliable andvalidmeasureofphysicalself-efficacyinchildren.9,10,20 BacktranslationwasperformedinordertousethePPASCin BrazilianPortugueseandSpanish.
Measurements of weight and height were recorded on thesame day that children completed the questionnaire, usingportablescale anda portablestadiometertoobtain theBMI,i.e.,weightinkgdividedbyheightinm2.Children weremeasuredbarefootandwithout outerwearina sepa-rateroom.BMIforagewascalculatedaccordingtogender, andchildrenweredividedintofourcategories,accordingto theinternationalclassificationbyColeetal.:normalweight, underweight,21overweight,andobese.22
Statisticalanalyses
TheKolmogorov---Smirnovtestwasperformedforage,BMI, andself-efficacy;theresultsshowedthatthevariablesdid nothave normal distribution (p-value <0.05). To compare eachoftheconsideredvariables(age,BMI,self-efficacy,and nationality)betweenmalesandfemales,theMann---Whitney Utestforindependentsampleswasused.Tocompareweight categories (underweight, normal weight,overweight, and obese),nationality(Brazilian,Italian,andSpanish),and gen-der, the chi-squared test was employed. To analyze BMI
differencesinrelationtonationality(Brazilian,Italian,and Spanish),separatelybygender,andtocomparetheweight categoriesandthetotalPPASCscore,Kruskal---WallisHtests were performed. The effect size was calculated for the Mann---WhitneyUtestandtheKruskal---WallisHtest.23
Finally,a linearregression wasperformed toevaluate, separately for gender, how the BMI increase, age, and nationalitycouldberelatedtototalperceivedphysical self-efficacy score, using the ‘enter’ method. SPSS (SPSS Inc. 2009. Statistics for Windows, version 18.0, USA) v.18was usedforallstatisticalanalysis.Statisticalsignificancewas setatp<0.05.
Results
Descriptive data on the sample are displayed in Table 1. ThemedianBMIwassignificantlyhigherforboyscompared withgirls(p=0.043;effectsize=0.059). Thefrequency of thinnessunderweightwashigheringirls(3.4%)thaninboys (1.5%).Ahigherpercentageofboyswereoverweight(12.3%) or obese (5.1%) than girls (12.2%, 2.8%), (p<0.001). The boys(PPASC19;18---21)reportedgreaterperceivedphysical self-efficacythangirls(PPASC18;17---19);(p<0.001;effect size=0.339).
TheBMIfactorshowednodifferencebetweencountries (Brazil, Italy, Spain), when analyzed separately by gen-der in the Kruskal---Wallis H test comparison. The total PPASC score was significantly different for weight cate-gories (p<0.001; effect size=0.003), with a mean rank self-efficacyscoreof724.53forunderweight,826.43for nor-mal weight,702.28 for overweight,and639.22for obese; and for nationality (p<0.001; effect size=0.003), with a meanrankself-efficacyscoreof687.55forBrazilian,812.89 forItalian,and722.11forSpanish.
Results from the linear regression model (Table 2), controlling for the confounders age, BMI, and nationality separatelybygender,demonstratedthatlowerPPASCscore wassignificantly relatedto higherBMI in boys(ˇ=−0.15; p<0.001;adjusted R2=0.044;F=12.98;p<0.001);in girls lower PPASC score was related to higher BMI (ˇ=−0.06; p=0.012), older age (ˇ=−0.29; p=0.001), and nation-ality; it was found that Brazilian girls had the lowest score (ˇ=−0.24; p=0.043; adjusted R2=0.032; F=9.53; p<0.001).
Discussion
Thepresentstudyshowedasignificantrelationshipbetween perceivedphysicalabilityandBMIinasampleof schoolchil-dren.Thisrelationshipemergedassignificantlydifferentfor boysand girls,andfor nationality inthelinear regression analysis.
Table1 Descriptivestatisticsforage,weightstatus,perceivedphysicalself-efficacyscore,andnationality.
Boys(n=787) Girls(n=773) Total(n=1560) p-Value
Ageofchilda 10(9.8---10.8) 10(9.6---11) 10(9.8---10.9) 0.77
BMIa 18.5(16.7---21.4) 18.3(16.4---20.6) 18.4(16.6---21) 0.043c
PPASCa 19(18---21) 18(17---19) 18(17---20) <0.001c
Weightgroups,n(%)b <0.001c
Underweight 24(3.0) 53(6.9) 77(4.9)
Normalweight 492(62.6) 486(62.9) 978(62.7)
Overweight 192(24.4) 190(24.6) 382(24.5)
Obese 79(10.0) 44(5.7) 123(7.9)
Nationality,n(%)b <0.001c
Brazilian 122(15.5) 158(20.4) 280(17.9)
Italian 587(74.6) 523(67.7) 1110(71.2)
Spanish 78(9.9) 92(11.9) 170(10.9)
BMI,bodymassindex;PPASC,PerceivedPhysicalAbilityScaleforChildren. Datashownasmedian(25thto75thpercentile)orn(%).
a Mann---Whitney’sUtest. b Chi-squaredtest.
c Statisticallysignificantdifferences(p<0.05).
byexcessiveweight,whichcontributestoincreasedconcern withself-perceptionsofphysicalabilities.
Of the children evaluatedin this study, approximately 24% of children had excess weight and 8% had obesity (Table1);these statisticsaresimilartothedata foundin the literature,18,26 and these percentages differ between genders.TheBMIresultsdemonstratenodifferenceamong thethreecountriesconsidered;however,itisimportantto highlight thattheprevalenceof overweightandobesityis highinthesecountries.Thesamplewascollectedin south-ern Brazil, a population of Italian and German descent, which is culturally similar to European countries such as ItalyandSpain, suggestingthatthe similaritiesin BMIare morebiologicalthansocio-culturallyderived.Besides, phys-icalself-efficacy may beless affected in a society where havingincreasedBMIisnormal.
In the linearregression model, for boys and girls, the increaseinBMIwasrelatedtoadecreaseinperceived phys-icalself-efficacy score(Table 2). Oneexplanationfor the
increaseinBMIanddecreaseinphysicalself-efficacyscore isthatsomeonewhoisclassifiedasoverweightorobesemay haveaself-perceptionofobesitythatmakeshimorherfeel unfittoperformphysicalactivity.Therefore,achildwhois classifiedasobeseavoidstakingpartinphysicalactivityso asnottobejudgedasbeingunabletoperform,andthus, entersaviciouscircle.Thephysicallyinactivelifestyleisa trigger toweightgain andvice versa.27 Furthermore,age andnationality also were predictors of low physical self-efficacyonlyforgirls.Theresultsunderlinedthedifferences inphysicalself-efficacyforgirlsrelatedtoolderageand dif-ferencesbetweenthecountries,sinceinItaly(meanrank: 408.17) there is a higher score of self-efficacy compared toBrazil(mean rank: 330.78).In Spain, girls(mean rank: 363.24)presentedsimilarPPASCscorestoboys(373.24).
Somelimitationsmayhave animpactonthe generaliz-ability of the present findings. The cross-sectional design of this study excludes statements about causality and directionalityin relation tothe variables of interest. The
Table2 Linearregressionmodeloftotal perceivedphysicalself-efficacyscore,separatelyforgender,andage,bodymass
index,andnationality.
Variables MultivariateB(stderror) Beta Multivariatet p-Value
Boys
AdjustedR2=0.044
Age −0.19(0.11) −0.060 −1.668 0.096
BMI −0.15(0.03) −0.202 −5.768 <0.001a
Nationality −0.10(0.14) −0.024 −0.678 0.498
Girls
AdjustedR2=0.032
Age −0.29(0.09) −0.119 −3.218 0.001b
BMI −0.06(0.03) −0.090 −2.518 0.012b
Nationality −0.24(0.12) −0.074 −2.031 0.043b
perceivedphysicalabilityis onlyoneofmanyfactorsthat influenceobesity.Otherpsychosocialaspectscorrelatingto physicalactivity couldbestudied infutureresearch,such asself-confidence andself-esteem,inordertoclarifythe factors that can promote healthy behaviors. Clearly, age andgendercanbeconsidered,becausetheyinfluencethese variables.Thedifferenceinsamplesizebetweencountries shouldbetakenintoaccount,however, thiscouldbe con-sidered as a strong point of the present work: physical self-efficacyinchildrenwasassessedusingthesame ques-tionnairein Brazil,Italy,andSpain.Moreover,theauthors considered the same international BMI classification cri-terion in each sample and a similar BMI distribution was observed in the three countries. Educational programs28 focused on developing physical skills could consider the associationbetweenphysicalself-efficacyandBMI,29,30and could be a means for improving the self-image of obese children,especiallyduringchildhood.
To conclude,these resultsreinforce the importanceof thepsychologicalaspectofobesity,astheperceived phys-ical self-efficacy and body mass index were negatively associatedinasampleofmaleandfemaleschoolchildren. Furthermore,ageandnationalityalsowerepredictorsoflow physicalself-efficacyonlyforgirls,giventhatlower physi-calself-efficacywasrelatedtobeingolderandBraziliangirls hadthelowestscore.
Funding
This study waspartlysupported by Fondazione delMonte di Bologna e Ravenna (Bologna, Italy), Protocol number 726BIS/2010andFundodeIncentivoàPesquisa(FIPE), Hos-pitaldeClínicasdePortoAlegre(HCPA,Brazil).
Conflicts
of
interest
Theauthorsdeclarenoconflictsofinterest.
Acknowledgements
ThisstudywassupportedbyFundodeIncentivoàPesquisa (FIPE),HospitaldeClínicasdePortoAlegre(HCPA,Brazil), andFondazione delMontediBolognae Ravenna(Bologna, Italy). AC and RML were the recipients of a grant pro-vided by the Brazilian government agency Coordenac¸ão deAperfeic¸oamentodePessoaldeNívelSuperior(CAPES). MPLH was the recipient of a grant provided by Con-selhoNacionaldeDesenvolvimentoCientíficoeTecnológico (CNPq).
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