Using Sensewear armband and diet journal to promote adolescents’energy balance know ledge and motivation

Senlin Chen,Xihe Zhu,Gregory J.Welk,Youngwon Kim,Jungm in Lee,Nthn F.Meier

aDepartment of Kinesiology,Iowa State University,255 Forker Building,Ames,IA 50011,USA

bDepartment of Movement Sciences,Old Dominion University,Norfolk,VA 23529,USA

Using Sensewear armband and diet journal to promote adolescents’energy balance know ledge and motivation

Senlin Chena,*,Xihe Zhub,Gregory J.Welka,Youngwon Kima,Jungm in Leea,Nathan F.Meiera

aDepartment of Kinesiology,Iowa State University,255 Forker Building,Ames,IA 50011,USA

bDepartment of Movement Sciences,Old Dominion University,Norfolk,VA 23529,USA

Purpose:Educating adolescents about energy balance(EB)is essential for effective weight control.This study utilized the Sensewear(SWA) armband and a diet journal to promote adolescents’EB know ledge and motivation.

Methods:Ninety sixth graders were random ly assigned into the experimental group(n=46)who utilized SWA and diet journal for 7 consecutive days or the controlgroup(n=44)who did not.Both groups were pre-and post-measured on EB know ledge,situational interest,and weight.The experimental group was tracked on motivation effort,energy expenditure(EE),and energy intake(EI).

Results:EB know ledge significantly increased and situational interest remained stable(except for total interest and enjoyment)over time,but these changes did not favor the experimental group.Situational interest and motivation effort were correlated w ith EE,EI,and/or EB.

Conclusion:Tracking EB using the SWA and diet journal is motivating buthas lim ited efficacy in promoting adolescents’EB know ledge.Using these two tools as educational technology in conjunction w ith a focused,systematic,and educational approach has the potential to leverage adolescents’EB know ledge,motivation,as well as behaviors for living an energy-balanced lifestyle.

CopyrightⒸ2013,Shanghai University of Sport.Production and hosting by Elsevier B.V.A ll rights reserved.

Energy expenditure;Energy intake;Health education;Motivation and health;Physical education;Situational interest

1.Introduction

The prevalence of overweight and obesity presents a major burden to our society and it needs to be strategically addressed.1,2Educating people about energy balance(EB)is essential for effective weight control.3—5EB denotes to the balance between energy expenditure(EE)and energy intake (EI),while EB know ledge refers to the concepts,principles, and strategies related to EB as well as its behavioral outcomes.6Research shows that adolescents have a deficiency in EB know ledge.4,7This deficiency(along w ith other individual and environmental factors)is likely to predispose youth to lose control of their body weight.6

Schools have been a common venue for intervention programs targeting EE,EI or both.8However,few studies have exam ined students’underlying EB know ledge and associated motivation for adopting healthy lifestyles.The current study employed a Sensewear armband monitor(SWA,BodyMedia Inc.,Pittsburgh,PA,USA)and a portable diet journal as part of a school-based program to promote EB know ledge in adolescents.Prior research shows that the SWA is efficacious to help obese adults lose weight.9—11However,no research has been reported on the utility of the SWA and diet journal in educating adolescents about EB in school settings.

Tracking EB on a daily basis is challenging and requires strong motivation.Three specific phases are involved in the task of tracking EB:forethought,performance,and selfreflection.12,13A person would gauge the value of the task before taking an action(i.e.,forethoughtphase),monitor their EE and EIbehaviors(i.e.,performance phase),and then reflectupon the outcome in terms of EB(i.e.,self-reflection phase). In addition,individuals are often attracted to participate in a task for its appealing features.Situational interest refers to the appealing effectof a task on an individual.14,15In theory,there are five determining sources for situational interest:novelty, challenge,attention demand,exploration intention,and instant enjoyment.14The novel task of tracking EB via SWA and diet journal is expected to generate situational interestand promote motivation on the task.

Prior research shows that the SWA and diet journal provide an accurate estimate of EB.16In addition,the SWA alone is efficacious in promoting weight loss among obese adults.9—11Using SWA and diet journal have the potential to enhance individuals’know ledge and behavior related to EB or weight management.To date,most obesity prevention related research has been focused on nutrition know ledge17—19or exercise know ledge,20,21butonly a few studies have exam ined EB know ledge.The available research does suggest that adolescents lack the necessary relational understanding of EB know ledge,4,7and EB know ledge is positively associated w ith moderate physicalactivity(PA)and negatively associated w ith television-view ing.4Further,adolescents’EB know ledge is directly related to the supporting natures of home5and school environments.7Therefore,it is important to empirically evaluate EB know ledge and its potential to influence motivation for adoption of appropriate weightmanagement behaviors.

The primary purpose of this study was to examine the effect of a week-long experiment that involved continuous tracking of EE and EI on adolescents’motivation and EB know ledge. Because EB know ledge is related to weight management, anthropometric data were also collected.The secondary purpose of the study was to exam ine the association between motivation(i.e.,situational interestand motivation effort),EB know ledge,and energy tracking outcomes.Hypothetically,the experience of using the SWA and diet journal would exert a significant impact on EB know ledge,and that situational interest and motivation effort would be positively associated w ith EB know ledge and energy tracking behaviors.

2.M ethods

2.1.Participants

This study was conducted in two ruralm iddle schools in a m id-weststate of the United States in 2012.Table 1 shows the demographic information of the sample.A totalnumber of 90 sixth graders(Male:n=44;Caucasian:n=71;Age: mean±SD=11.71±0.53)were recruited from eight classes on a voluntary basis.The sample has BM Iranging from 12.14 to 34.80(mean±SD=21.06±4.55),37%of whom were overweight (i.e., 85%ile BM I for 12-year-old adolescent=21.11).22The number of participants per physicaleducation(PE)class varied from 5 to 16(Median=11.5). Sixth graders were chosen because they are at early adolescence,an age threshold when obesity/overweight ratio starts to surge.1,2In a sustainability perspective,intervention at this period is crucial for weight control and obesity prevention.

Table 1 Demographic information of the sample.

The participants were random ly assigned into the experimental group(n=46)or the controlgroup(n=44;Table 1). The participants in the experimental group utilized the SWA and diet journal for 7 consecutive days.They were provided w ith personalized informational feedback for one time follow ing a standardized procedure in the m iddle of the week. Details regarding the treatment are available in the Procedure section below.The control group did not use the two tools until the end of the study to ensure educationalequality.Prior to data collection,approvals from the university Institutional Review Board and school districts were granted;Parental/ guardian consents and m inors’assents were secured.

2.2.Instruments

2.2.1.EB know ledge

EB know ledge was pre-and post-tested using a standardized w ritten test.The test had eight multiple-choice questions and one open-ended question.The know ledge scope included declarative,procedural,and conditional know ledge related to EB.For example,a question thatasked about the participants’declarative know ledge stated:“Which one of the follow ing activities requires energy the most?”The choices were“a. Having lunch,b.Watching TV,c.Jumping rope(the correct answer),d.Stacking cups”.The responses were graded to the answer key and the sum of correct scores was reported as the EB know ledge performance.The performance scores ranged from 0 to 8.The w ritten test demonstrated sufficient content validity by an expert panel using the Delphi method.23It also showed acceptable internal consistency(Cronbach’sα=0.52) and test—retest reliability(r=0.71).

2.2.2.Motivation effort

Motivation effort was reflected by the extent to which the participants utilized the SWA and diet journal.The SWA is a sophisticated instrument that can detect subtle motions.Specifically,the SWA recorded the percentage of time and the number of days that the participants wore it on body over theweek-long experiment.In addition,the diet journal captured the number of days that the journal was utilized during the experiment.To ensure data trustfulness,a trained data analyst processed the data that were documented by the diet journal and the principal investigator verified the accuracy.The quantification of these two sources of data measured the participants’motivation effortwhen tracking EE and EI.

2.2.3.Situational interest

Situational interest was measured using the Situational InterestScale(SIS).14The SIS consists of 24 5-point Likert type items(5=strongly agree,1=strongly disagree).The responses reflected the participants’perceptions of novelty,challenge, attention demand,exploration intention,and instantenjoyment. Forexample,an item thatmeasured novelty is stated:“This is a new-fashioned activity for me to do”.The participants were instructed to reference the task of tracking EB as the“activity”while completing the SIS.The SIS wasdeveloped and validated using a sample of m iddle school students,and displayed consistently acceptable constructvalidity(λranged from 0.60 to 0.90)and internal consistency reliability(Cronbach’sαranged from 0.63 to 0.91)across severalsub-samples.14

2.2.4.EI

EI was measured by a self-designed portable diet journal. The diet journal prompts users to enter the follow ing information upon consumption:time of entry,type of food/drink, amount,unit,brand,and way of preparation.The researchers provided detailed instructions on how to document nutrition information.When difficulty arose in determining portion sizes,the participants were advised to use the follow ing methods:(a)reading food or beverage labels;(b)referring to the examples provided in the diet journal;and(c)seeking help from adults or more know ledgeable others.At the end of the study,a trained data analyst entered the data from each diet journal into Nutritionist Pro(Axxya Systems™,Stafford,TX, USA),which generated EIdata(in kcal).The Nutritionist Pro was selected for diet analysis because of its comprehensive database,high efficiency of the search engine in finding foods, adaptable output feature,and affordable cost.24The above method to measure EI was previously used and was found accurately estimating EI among a sample of overweight/obese adults.16

2.2.5.EE

EE was measured by the SWA.SWA is a non-invasive, w ireless multi-sensor monitor worn on the left triceps using an adjustable strap.It relies on several parameters(i.e.,heat flux,galvanic skin response,skin temperature,near body temperature,and motion being determ ined by a tri-axial accelerometer)to measure EE(in kcal),time spent in PA of various intensities(in minute),and other movement outcomes.The SWA is user-friendly and has showed sound criterion validity and test retest reliability for assessing freeliving EE.25

2.2.6.Weight,height,body mass index(BMI),estimated EB,and actual EB

Weight was measured using a digital weight scale(Tanita HD-366;Tanita,Arlington Heights,IL,USA).The scale took measurementofweight in kilogram,which was also converted to pound and ounce.Height was measured by the Seca 213 stadiometer(Seca™,Hanover,MD,USA).The stadiometer provided measurement in centimeter.BM I was calculated to adjustnaturalbody grow th.The estimated EB was obtained by calculating the difference between EE and EI;while actual EB was obtained through a mathematical conversion from body weight.Because one pound of body fat can be deemed as 3500 kcals of energy,actual EB was computed by multiplying the weight changed(in pound and ounce)and 3500.6

2.3.Procedure

The data collection procedure was carried out step by step as described below.During the fi rst school visit,class rosters were obtained from the PE and/or health teachers.Because there were a number of students per class participated in this research project,the class rosters were reduced w ith participants who were coded by de-identified numbers.The participants were random ly assigned by the lead author into the experimental or the control groups.Overall,each class had roughly even number of participants per group.During the second school visit,the participants were informed of their group assignment(i.e.,experimental or control group).All participants were pre-measured on EB know ledge,situational interest,weight,height,and demographic variables(age, gender,ethnicity,and date of birth).During the third school visit,the experimental group was gathered and distributed w ith an SWA and a diet journalper participant.Instructions on how to use the two tools as well as their utility features were carefully delivered and questions were addressed immediately. The participants were informed to wear the SWA continuously for 7 days except under follow ing circumstances:(a)taking a shower,(b)sw imm ing,(c)playing American football and contact martial arts.They were further informed to carry the diet journal wherever they go and document immediately everything they ate or drank.During the fourth school visit (day 3 or 4 of the week),the experimentalgroup was provided w ith personalized informational feedback on the ongoing usage of the SWA and diet journal.The feedback process followed a standardized procedure.Specifically,a trained data collector summoned participants one by one(experimental group only)to a gymnasium corner,then checked and conveyed to each participant the summary data:total EE, number of steps,and m inutes of MVPA accumulated on the previous day.Then,the data collector checked each participant’s diet journal for consistentuse.Rem inders were offered for participants to log the diet journal immediately upon consumption to improve recall accuracy.During the fi fth school visit,all participants(both experimental and control groups)were post-measured on EB know ledge,situational interest,weight,and height.Lastly,to ensure educational equality,the control group(through personal willingness)received the delayed treatmentusing the SWA and diet journal for 7 days.

2.4.Data analysis

Data analyses consisted of four steps to address the research questions.First,descriptive analyses(e.g.,mean±SD)were conducted to reveal data distribution of the variables.Second, pairedttests were operated to examine the time effect on changes in EB know ledge,situational interest,and weight. Third,two analyses of variance(ANOVA)were conducted to determ ine the change in situational interestand EB know ledge across condition(experimentalvs.control)and weight status (BM I＞85%ilevs.BM I≤85%ile).Fourth,a bivariate correlation analysis was performed to discern the association between motivation and EB know ledge as well as energy tracking outcomes(i.e.,estimated EE,EI,and EB).SPSS19.0 (IBM Corporation,Armonk,New York,USA)was employed for data analyses w ith a 95%confidence interval(α=0.05).

3.Results

3.1.Descriptive results

Table 2 shows the descriptive results of the variables before and after the experiment.Overall,the participants performed moderately on the standardized know ledge teston an 8-point scale confi rming a need to promote EB know ledge at this grade level.A ll situational interest constructs except the perceived challenge demonstrated high mean scores(mean value＞4.0 on the 5-point scale).These results indicate that the participants perceived relatively high situational interest in using(experimentalgroup)or seeing(controlgroup)the SWA and the diet journal,although tracking EE and EI did not appear to be a very challenging task for them.In addition,as expected,weight remained stable over the week.

Table 3 shows an obvious discrepancy between the EIand the EE for the experimental group.EE was reported to be higher than EI(mean difference=-4745.95 kcal),which led to a negative EB.This imbalance between EE and EI considerably deviated from the actual EB obtained from weight change.Further,the SWA was utilized more persistently than the diet journal.The above results indicated that the EI was under-reported compared to EE estimate.

3.2.Effect of the treatment

Table 2 also shows the inferential statistical results across time(pre-vs.post-)for all participants,the experimental group,and the controlgroup.Over the week-long experiment, the participants overall significantly increased EB know ledge (t=-2.49,p=0.02,Cohen’sd=0.20).However,ANOVA revealed that this increase did not favor the experimental group over the control(p＞0.05).The result indicates that the acquisition of EB know ledge is not attributable to the weeklong experience of tracking EE and EI using the SWA and the diet journal,respectively.

As for situational interest,the perceptions of exploration, novelty,attention demand,and challenge remained stable;but total interest and perception of enjoyment decreased over the week(total interest:t=5.20,p＜0.01,Cohen’sd=0.50; enjoyment:t=2.53,p＜0.01,Cohen’sd=0.31).The decline in these two constructs was not statistically significant between the experimental and control groups(p＞0.05).The result indicates that the SWA and the diet journalwere initially perceived to be situationally interesting but the adolescent users’general interest and perceived enjoyment attenuated w ith prolonged use.Neither EB know ledge nor situational interested differed between normal and overweight participants(p＞0.05).

3.3.Association between motivation and outcome variables

Table 4 illustrates the bivariate correlations coefficients among motivation(situational interest and motivation effort) and outcome variables(i.e.,EB know ledge,EE,EI,and estimated EB).Situational interest and motivation effort were correlated w ith the outcomes variables.Specifically,perceived exploration was negatively correlated with EI(r=-0.40,p＜0.05)and EB(r=-0.36,p＜0.05).This finding indicates that the participants reported lower EI and EB (EB=EI-EE)when energy tracking was perceived worthy of more exploration.This is noteworthy since participantswere notspecifically asked to change theirbehavioror to try to lose weight.

Table 2 Changes over the week-long experiment(mean±SD).

Table 3 Descriptive information of the variables measured in the experimental group (n=46)(mean±SD).

The number of days of using the diet journalwas positively correlated w ith EI(r=0.65,p＜0.01)and estimated EB (r=0.43,p＜0.01);and percentage of time in using the SWA was positively correlated w ith EE(r=0.71,p＜0.01).These two results demonstrated that as the participants put forth more motivation effort to utilize the SWA and diet journal, they tended to demonstrate more desirable energy tracking behaviors and outcomes.The above results illustrate that motivation plays an important role in tracking EE and EI.

4.Discussion

Using an experimental design,this empirical study found that EB know ledge was moderate in both pre-and postmeasurements.The results are consistent w ith previous research that there is a need for EB know ledge promotion in adolescence.4,7A lthough there was an increase in EB know ledge over the week,the increase did not significantly favor those in the experimentalgroup.Thus,it is concluded that the SWA and diet journal alone were notsufficient for promoting sixth graders’EB know ledge,at least during a very short period of time of monitoring(1 week).The modest results may also be due to the lim ited amount of informational feedback provided to the participants.Providing additional feedback or building the results more directly into the curriculum may help in promoting adolescents’awareness of EB.Previous largescaled educational interventions in both community-based26and school-based programs21proved to be effective in promoting children and/oradolescents’health-related know ledge. For example,Sun et al.21conducted a large-scaled curriculum intervention among 5717 third,fourth,and fi fth grade students in 30 schools.Itwas found that children who experienced the innovative curriculum learned more and at a faster rate the know ledge abouthealth-related fi tness and nutrition compared to their counterparts who received a control curriculum.21Future intervention studies that use the SWA and diet journal to promote EB know ledge should consider incorporating the two tools into focused,coherentcurriculum and instruction to reap significant treatment results.

The experience of utilizing the SWA and diet journal seemed effective in enticing and retaining the adolescents’motivation(high mean values except for total interest and perceived enjoyment)which,in turn,exerted an impact on energy tracking outcomes.The adolescents started w ith relatively high situational interest(mean＞4 on a 5-point scale) but then gradually leveled off(especially for total interestand perceived enjoyment).More importantly,exploration intention,a particular constructof situational interest,was found to be negatively correlated w ith EI.This result is interesting if it is interpreted along w ith the fact that the adolescents utilized the SWA more persistently than the diet journal.The combined results imply that the adolescents may be more attracted to explore the features of the SWA for tracking EE than to explore the diet journal for tracking EI.Motivation researchers asserted that motivation energy can be channeled toward different directions or purposes.27In this current study,the adolescents’higher motivational energy(originated from situational interest)may have been devoted to using the SWA than to using the diet journal.

Motivational effort is required in all three phases(forethought,performance,and self-reflection)of self-regulatory behaviors,when engaging in a task.12,13The adolescents’motivation effort to track EB was found to vary from personto person and that higher level of motivation effort(i.e.,more persistent use of the SWA and diet journal)was positively associated w ith EE and EI tracking outcomes.This finding illustrates the importance of encouraging adolescents to cognitively and/or meta-cognitively regulate themselves to promote desirable energy tracking behaviors.12,13Comparatively,the adolescents’motivation effort to track EE via the SWA was higher than that to track EI via the diet journal, which partially led to the discrepancy between EE and EI outcomes.Future research and practice should increase the appealing features of the diet journal to make it more intuitive and user-friendly.For example,as technology advances, innovative smart phone applications have emerged for users to more conveniently log one’s daily nutrition.It appears to be a prom ising area of research to investigate whether these validated smart phone applications could replace the traditional pencil—paper diet journals in obesity prevention research.

Table 4 Correlation matrix for motivation and outcome variables.

From a sustainability perspective,equipping adolescents w ith EB know ledge,motivation,and behaviors could help address the obesity crisis that burdens our society.28As expected,this study did not show a significantweight change as a resultof using the SWA and the diet journal.Unlike previous studies in obese adults that demonstrated significant weight reduction over longer period of time,9—11this current study, primarily due to the short duration of treatment,did not anticipate weight change in adolescents.It is acknow ledged that as adolescents are still developing toward maturity,promoting know ledge and behaviors related to EB is more important than focusing on weight reduction.For most of the healthy adolescents,maintaining a physically active lifestyle and eating in moderation and variety may be more appropriate and realistic than losing weight.Future studies that intend to intervene in weight reduction among obese or overweight adolescents may have to provide treatment for a longer duration(i.e.,8 weeks or 9 months),as illustrated in previous research on adults.9—11Also,it is known that achieving significantweight loss in a shortperiod of time is notpossible or even recommended since weight“regain”is often observed not long after the intervention was delivered.29

The findings from this research should be interpreted w ith several lim itations.First,the research sample was primarily constituted by Caucasian participants(80%).The findings are only generalizable to adolescents of sim ilar demographic characteristics.Second,the usage of diet journal varied considerably from person to person,although clear instructions were provided by the researchers.Shown in Table 3, the SD for EI,EB,and the difference between estimated and actual EB are large.Unlike adults who utilized the diet journal consistently,16adolescents in this study did not find the diet journal attractive.An online tool or an App m ight be more engaging and promote more consistent use.Third,the treatment effect of the experiment was limited by the short duration and modest degree of informational feedback.Future research should consider increasing the treatment magnitude (e.g.,8 weeks and more frequent feedback)to elevate adolescents’motivation,know ledge,and behavior related to EB.

5.Conclusion

In summary,this study took the initiative to incorporate the SWA and diet journal into adolescents’daily life as an attempt to promote EB know ledge and motivation.EB promotion should be taken seriously in the effort to battle the obesity epidem ic that burdens our societies.28Intentional educational intervention should targetboth home and schoolenvironments where adolescents spend most of their dates.5,30Although a greatnumber of school-based interventions have been done to promote the behavioraloutcomes of MVPA and healthy eating (Katz et al.’s8review),research efforts that incorporate selfmonitoring tools such as the SWA and portable diet journal to promote adolescents’motivation,EB know ledge,and behaviors are limited.This present study generated evidence supporting the applicability of the SWA and diet journal in enticing motivation for tracking EB among m iddle school students.Participating in the research project caused m inimal interruptions to regular school activities(e.g.,instructional time,class participation).However,the week-long experiment demonstrated limited efficacy in promoting adolescents’EB know ledge.Schools,especially health education and physical education professionals,are encouraged to incorporate the SWA and the diet journal or their less expensive equivalents into regular curriculum and instruction.Using these two tools as educational technology in conjunction w ith a focused, systematic,and educational approach has the potential to enhance adolescents’EB know ledge,motivation,as well as behaviors for living an energy-balanced lifestyle.In addition, engaging parents to provide a supportive home environment where adolescents could resort to the necessary help in tracking and manipulate EB would further increase the effectiveness of educational interventions.

Acknow ledgment

This work was supported by Iowa State University College of Human Sciences.

1.Dietz WH.Overweight in childhood and adolescence.N Engl J Med2004;350:855—7.

2.Ogden CL,CarrollMD,Curtin LR,Lamb MM,Flegal KM.Prevalence of high body mass index in US children and adolescents,2007—2008.J Am Med Assoc2010;303:242—9.

3.Katz DL.Unfattening our children:forks over feet.Int J Obes(Lond)2011;35:33—7.

4.Nelson MC,Lytle LA,Pasch KE.Improving literacy aboutenergy-related issues:the need for a better understanding of the concepts behind energy intake and energy expenditure among adolescents and their parents.J Am Diet Assoc2009;109:281—97.

5.Slater ME,Sirard JR,Laska MN,Pereira MA,Lytle LA.Relationships between energy balance know ledge and the home environment.J Am Diet Assoc2011;111:556—60.

6.Dunford M.Fundamentals ofsportand exercise nutrition.Champaign,IL: Human Kinetics;2010.

7.Chen S,Chen A.Youth physical activity behavior and energy-balance know ledge:an expectancy-value perspective.J TeachPhys Educ2012;31:329—43.

8.Katz DL,O’Connell M,Njike VY,Yeh MC,Nawaz H.Strategies for the prevention and control of obesity in the school setting:systematic review and meta-analysis.Int J Obes(Lond)2008;32:1780—9.

9.Barry VW,M cClain AC,Shuger S,Sui X,Hardin JW,Hand GA,et al. Using a technology-based intervention to promote weight loss in sedentary overweight or obese adults:a random ized controlled trial study design.Diabetes Metab Syndr Obes2011;4:67—77.

10.Shuger SL,Barry VW,Sui X,M cClain A,Hand GA,Wilcox S,et al. Electronic feedback in a diet-and physical activity-based lifestyle intervention for weight loss:a random ized controlled trial.Int J Behav Nutr Phys Act2011;8:41.

11.Walsh SA.Efficacy of three eight-week lifestyle interventions on weight loss and cardiovascular disease risk factors in obese adults.Ames:Iowa State University;2011[Dissertation].

12.Kitsantas A,Kavussanu M.Acquisition of sport know ledge and skill:the role of self-regulatory processes.In:Zimmerman BJ,Schunk DH,editors.Handbook of self-regulation on learning and performance.New York: Routledge;2011.p.217—33.

13.Zimmerman BJ.Investigating self-regulation and motivation:historical background,methodological developments,and future prospects.Am Educ Res J2008;45:166—83.

14.Chen A,Darst PW,Pangrazi RP.What constitutes situational interest? Validating a construct in physical education.Meas Phys Educ Exerc Sci1999;3:157—80.

15.Hidi S,Anderson V.Situational interest and its impact on reading and expository w riting.In:Renninger KA,Hidi S,Krapp A,editors.The role of interest in learning and development.Hillsdale,NJ:Law rence Erlbaum Associates;1992.p.215—38.

16.M cGuire AS.Utility of the SP3 and the WMS for evaluating energy balance in adults.Ames:Iowa State University;2010[Dissertation].

17.Fehlman MM,Dake JA,M cCaughtry N,Martin J.A pilot study to exam ine the effects of a nutrition intervention on nutrition know ledge, behaviors,and efficacy expectations in m iddle school children.J Sch Health2008;78:216—22.

18.Lakshman RR,Sharp SJ,Ong KK,Forouhi NG.A novel school-based intervention to improve nutrition know ledge in children:cluster random ized controlled trial.BMC Public Health2010;10:123.

19.Valliant MW,Empliaincourt HP,Wenzel RK,Garner BH.Nutrition education by a registered dietitian improves dietary intake and nutrition know ledge of a NCAA female volleyball team.Nutrients2012;4:506—16.

20.DiLorenzo TM,Stucky-Ropp RC,Vander Wal JS,Gotham HJ.Determ inants of exercise among children.II.A longitudinal analysis.Prev Med1998;27:470—7.

21.Sun H,Chen A,Zhu X,Ennis CD.Curriculum matters:learning sciencebased fi tness know ledge in constructivist physical education.Elem Sch J2012;113:215—29.

22.Ogden CL,Fryar CD,Carroll MD,FlegalKM.Mean body weight,height, and body mass index,United States 1960—2002.AdvData2004;347:1—17.

23.Linston HA,Turoff M,editors.The Delphi method:techniques and applications.Available at:http://is.njit.edu/pubs/delphibook.[accessed 25.03.2013].

24.Stumbo P.Considerations for selecting a dietary assessment system.J Food Compost Anal2008;21(Suppl.1):S13—9.

25.Johannsen DL,Welk GJ,Sharp RL,Flakoll PJ.Differences in daily energy expenditure in lean and obese women:the role of posturalallocation.Obesity(Silver Spring)2008;16:34—9.

26.Young DR,Haskell WL,Taylor CB,Fortmann SP.Effect of community health education on physical activity know ledge,attitudes,and behavior: the Stanford Five-City Project.AmJEpidemiol1996;144:264—74.

27.Chen S,Chen A,Zhu X.Are k-12 learners motivated in physical education?A meta-analysis.Res Q Exerc Sport2012;83:36—48.

28.Caw ley J,Meyerhoefer C.The medical care costs of obesity:an instrumental variables approach.J Health Econ2012;31:219—30.

29.Cooper Z,Doll HA,Hawker DM,Byrne S,Bonner G,Eeley E,et al. Testing a new cognitive behavioral treatment for obesity:a random ized controlled trial w ith three-year follow-up.BehavResTher2010;48:706—13.

30.Sallis JF,M cKenzie TL,Beets MW,Beighle A,Erw in H,Lee S.Physical education’s role in public health:steps toward and backward over20 years and HOPE for the future.Res Q Exerc Sport2012;83:125—35.

Received 18 April 2013;revised 12 June 2013;accepted 23 July 2013 Available online 25 September 2013

*Corresponding author.

E-mail address:slchen11@iastate.edu(S.Chen)

Peer review under responsibility of Shanghai University of Sport.

2095-2546/$-see front matter CopyrightⒸ2013,Shanghai University of Sport.Production and hosting by Elsevier B.V.A ll rights reserved. http://dx.doi.org/10.1016/j.jshs.2013.07.003