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School-Based Interventions on Childhood Obesity
School-Based Interventions on Childhood Obesity A Meta-Analysis Consuelo Gonzalez-Suarez, PhD, MD, Anthea Worley, MA, Karen Grimmer-Somers, PhD, Valentine Dones, MSPT Background: Over the past decade, childhood obesity has been recognized as an increasing health problem worldwide. It is a predictor of obesity during adulthood, which is strongly linked to chronic lifestyle diseases. Purpose:
This paper aims to evaluate the effectiveness of school-based programs in the prevention and management of childhood obesity.
Methods:
A comprehensive literature search was undertaken for RCTs and clinical controlled trials on school-based interventions that addressed childhood obesity, published between 1995 and 2007. The papers included for the meta-analysis were those in which ORs or standardized mean differences and their 95% CIs were reported or could be calculated from available data.
Results:
Meta-analysis showed that the odds of participants’ being overweight and obese in the school-based intervention programs compared with the control arm were significantly protective in the short term (OR⫽0.74, 95% CI⫽0.60, 0.92). Interventions that were conducted for more than 1 year had a higher OR of decreasing the prevalence of obesity. However, intervention programs were not effective in decreasing BMI compared with control treatments, with a weighted mean difference of ⫺0.62 (95% CI⫽⫺1.39, 0.14).
Conclusions: This meta-analysis showed that there was convincing evidence that school-based interventions are effective, at least short-term, in reducing the prevalence of childhood obesity. Longer-running programs were more effective than shorter programs. (Am J Prev Med 2009;37(5):418 – 427) © 2009 American Journal of Preventive Medicine
Background
C
hildhood obesity has been recognized as an increasing health problem worldwide over the past decade. In the U.S., the prevalence of overweight children aged 5–14 years rose from 15% in 1973 to 32% in 1994, while that of obesity increased from 5% in 1973 to 22% in 1994.1 Similar increases have been reported in countries such as the United Kingdom, Germany, Australia, and China.2–5 Childhood obesity has been associated with diseases in childhood such as asthma, early-onset diabetes mellitus, and childhood hypertension.6 It has also been shown that childhood obesity is a predictor of obesity during adulthood.4,7 High BMI in adulthood is strongly linked to chronic and nonreversible diseases, such as hypertension, diabetes mellitus, coronary arterial disease, occlusive cerebrovascular disease, and degenerative joint disease. ImFrom the Centre for Allied Health Evidence (Gonzalez-Suarez, Worley, Grimmer-Somers), University of South Australia, Adelaide, Australia; and University of Santo Tomas (Gonzalez-Suarez, Dones), Manila, Philippines Address correspondence and reprint requests to: Consuelo B. Gonzalez-Suarez, PhD, MD, Center for Research on Movement Science, Thomas Aquinas Research Complex, University of Santo Tomas, Espana St, Manila, Philippines 1008. E-mail: cgsuarez@ mnl.ust.edu.ph.
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portantly, a study by Burke and colleagues8 showed that being overweight between ages 14 and 19 years is associated with increased mortality after age 30 years from systemic diseases. It is therefore important to recognize and treat overweight and obesity in children. Research studies on the effectiveness of methods in controlling childhood obesity have variably tested the following individually or in combination: ●
● ● ●
change in diet (such as reducing the intake of high-density and high-caloric food and replacing it with foods that are high in fiber); decrease in sedentary behavior; increase in physical activity through enrollment in a structured physical fitness program; behavior modification.
Most research has been school-based and has been characterized by the delivery of nutritional education, promotion of decreased TV viewing and sedentary behavior through pamphlets and lectures, modification of the food being provided by school canteens, and physical activity programs.9 –11 All studies are conducted under the premise that sustainable changes in diet and physical activity will be achieved if they are carried into adulthood and will prevent obesity in later years. However, there has
Am J Prev Med 2009;37(5) © 2009 American Journal of Preventive Medicine • Published by Elsevier Inc.
0749-3797/09/$–see front matter doi:10.1016/j.amepre.2009.07.012
been unconvincing evidence on the effectiveness of school programs to reduce any measure of overweight and obesity in children, either short-term or long-term, from systematic reviews of the literature.12–16
Objectives This paper reports on a meta-analysis that was conducted on studies to evaluate the evidence for the effectiveness of school-based programs in the management of childhood obesity in terms of BMI, percentage of body fat, waist girth, triceps skinfold, and waist– hip ratio.
Methods Participants The review considered schoolchildren of any nationality who were of normal BMI, overweight or obese, and in preadolescent and adolescent phases, with fatness classified by an age- and gender-specific cutoff point system developed by the International Obesity Task Force or by country-specific norms. Children of normal BMI were included in the study because the study investigated both the prevention and treatment of overweight and obesity.
terms undertaken in the following databases: Ovid (MEDLINE, PsycINFO, EMBASE, EBM Reviews), Cochrane Library, CINAHL, Current Contents, BioMed Central, AustHealth, SCOPUS, TRIP (Turning Research into Practice), Science Direct, EMBASE, Health Source: Nursing/Academic Edition, AMED, PubMed, and Academic Elite. The identified keywords were as follows: Concept 1: childhood obesity, adolescent obesity, youth obesity, child obesity Concept 2: treatment or management or prevention or program The second phase was a search of the reference lists and bibliographies of all potentially relevant articles identified in Phase 1. All studies identified during the database search and search of the reference lists were assessed for relevance to the review based on information provided in the title and abstract. If considered relevant, the full text of the paper was retrieved for further analysis of whether the study met the inclusion criteria.
Methodologic Quality
The outcome measures examined in the review included BMI, waist girth, percentage body fat, and triceps skinfold. For the purpose of this meta-analysis, short-term outcomes were considered to be those measured immediately after completion of the intervention, while long-term outcomes were those that were measured at least 6 months after completion of the intervention program.
The studies were appraised by two independent reviewers for methodologic quality before inclusion in the meta-analysis. Should any disagreement have arisen between the reviewers, it would have been resolved by adjudication of a third reviewer. Inter-rater reliability was tested using Cohen’s kappa coefficient. The kappa coefficient was 0.75. A quality score was set at 60% of the possible total score, which weights the findings of the review toward studies of high internal methodologic quality that are externally valid. Methodologic quality was assessed using the JBI (Joanna Briggs Institute) Critical Appraisal of Evidence Effectiveness tool (see Appendix A, available online at www.ajpm-online.net).17 This critical appraisal tool has been endorsed by the JBI, and use of this tool is mandated for any systematic reviews to be undertaken using the JBI framework. Because the interventions included classroom activities and improvement or addition of activities in physical education class, blinding of the participants to treatment allocation was improbable. Keeping this in mind, the highest possible score that a study could obtain was 10 (as Question 2 was removed from the critical appraisal tool for this review). Question 2 asked, Were participants blinded to treatment allocation? A score of 6 and above was determined as appropriate methodologic quality, and thus studies of six or more would be included in the review (representing 60% of the possible total score). No priority was given to completion of any specific criteria in the methodologic quality checklist.
Study Design
Data Extraction and Analysis
The meta-analysis included only those RCTs and clinical controlled trials that had high methodologic critical appraisal scores (more than 60% of the possible criteria met).
Data were extracted using the data extraction tool developed by the JBI.17 Data extracted included sample size, subject age and gender, intervention(s) description and control group(s) description, outcome measures, length of intervention, confounders, comorbidities, short- and long-term results, significance, relevance, and generalizability. The papers included in the meta-analysis were also those in which odds ratio (ORs) or standardized mean differences (SMDs) and their 95% confidence interval (CI) were reported or could be calculated from available data. Where applicable, results from comparable studies were pooled in a statistical analysis using the Review Manager software (RevMan) from the Cochrane Collaboration.18 ORs were used in data that were in
Intervention The interventions that were considered for inclusion in the review were any deliberate approach to ● ● ● ●
increase physical activity, improve dietary behaviors, modify poor exercise or dietary behaviors, or a combination of the above approaches.
However, the interventions were relevant to this review only if they were delivered in a school-based program, with the aim of addressing overweight and obesity in the target population.
Outcome Measures
Language and Date Restrictions Searches included publications in English only, published between 1995 and 2007. This time frame was established because of a large worldwide increase over the past decade in combating childhood obesity.
Search Strategy of Literature Sources A two-step search strategy was employed. The first phase was a comprehensive search using identified keywords and index
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binary form (prevalence of overweight and obesity) while weighted mean differences (WMDs) were used in data that were in continuous form (BMI, waist circumference, waist– hip ratio, and triceps skinfold). Each measure of fatness was analyzed separately. Where studies reported mean changes in outcome measures from baseline to post-intervention for each group, data were entered in RevMan with the corresponding number of participants and ␦s (pooled SD). For studies that reported both pre- and post-intervention values but without mean change, the change was computed by subtracting the baseline measurement from the post-intervention measurement. The ␦s (pooled SD) was estimated using the equation19
␦s⫽兹[(␦pre 2⫹␦post 2) ⁄ 2]. When SE was reported, the pooled SD was computed using ␦⫽SE 公n. Significance in CIs for ORs is identified by the 95% CI not encompassing 1, and for mean differences, not encompassing 0. To obtain the WMD with 95% CI for both the treatment and control groups, a random effects model was used when heterogeneity was present (p⬍0.05) and if the computed I 2 was more than 75%; otherwise, the fixed effects model was used.
Results The search identified 41 papers based on their title for possible inclusion in the review, of which 19 papers were included in the meta-analysis (Figure 1).
Excluded Studies Fifteen papers were excluded because they did not meet the inclusion criteria. Six papers20 –25 had no outcomes for measures assessing overweight and obesity; four papers11,26 –28 included preschoolers as the participants; two papers29,30 had interventions that were community-based; one paper31 had a family-centered intervention; one paper32 had height and weight self-reported by participants; and another paper33 had only preliminary findings of baseline measurements. Four further studies34 –37 were excluded because of poor methodologic
quality. Three papers38 – 40 were excluded because their ORs or SMDs and 95% CIs were not reported or could not be calculated from available data. Of the 19 papers included, three were follow-up studies41– 43 (see Figure 1 and Appendix B, available online at www.ajpm-online. net, for full details of included studies).
Outcome Measures Body mass index was reported in all included papers. This was either used as a cutoff point for overweight and obesity to test the effectiveness of the intervention in decreasing the prevalence of overweight in the sample population or by obtaining the change in mean BMI. The other measures of obesity used in the included studies were waist girth; triceps skinfold thickness; percentage body fat, which was measured by bioelectric impedance, dual energy absorptiometry, or by the sum of skinfolds; waist– hip ratio; and subscapular skinfold thickness (Table 1).10,42–58 Most papers used multiple measures of obesity, except for the studies by Jiang et al.50 and Kafatos et al.,43 which used BMI only. Only the studies by James et al.,46 Huang et al.,56 and Manois et al.49 reported mean change with SD and did not require additional computation. For the study by Manois and colleagues,49 the percentage change in triceps skinfold required computation. All other papers required computation by the researchers, as described in the Methods section.
Interventions The interventions reported in the included studies were generally designed to decrease overweight by increasing physical activity, to decrease participation in sedentary activities, and to decrease intake of food high in fat and sugar content. This was achieved by having classroom lessons that emphasized the reduction of consumption of high-fat, sugary foods; increase in intake of fruits and vegetables; and the importance of increasing physical activity. In addition to this, physical education classes were modified so that a larger percentage of the time period was spent in moderate-to-vigorous physical activity.
Strategies
Figure 1. CONSORT diagram of papers included in the meta-analysis
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Most of the studies used multipronged intervention strategies. In the study reported by Grey and coworkers,58 the intervention was improved by telephone calls that focused on enhancing self-image. Modifications in the school environment, such as providing healthy foods in schools canteens, were incorporated in the management strategy reported by Kain et al.54 Parental involvement was included in the interventions reported by Kain and colleagues54 and Danielzik et al.42 Single interventions were reported in five studies,45,46,51,53,55 reflecting modification in classroom curriculum or variations in physical education or physical
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Table 1. Outcome measures available for meta-analysis Study 42
Danielzik (2007) Kafatos (2005)43 Spiegel (2006)44 Lazaar (2007)45 Gorthmaker (1999)10 James (2004)46 James (2007)41 Coleman (2005)47 Manois (1999, 2002)48,49 Jiang (2007)50 Robinson (1999)51 Graf (2005)52 Carrel (2005)53 Kain (2004)54 Yin (2005)55 Huang (2007)56 Harrel (1996)57 Grey (2004)58
Prevalence
BMI change
Waist girth
Body fat
Waist–hip ratio
Triceps skinfold
— — X X X X — X X X — — — — — — — —
X X — — X X X X X X X X X X X X X X
— — — — — X X — — — X X
— — — — — — — — — — — X X — X X X —
— — — — — — — — — — X X — — — — — —
X — — — — — — — X — X — — X — — — —
X X — — X
activities held in schools. Robinson51 provided lessons that emphasized reduction of hours spent in TV viewing, while James and colleagues46 allotted a 1-hour session each term that emphasized decrease in intake of carbonated drinks and the importance of water. On the other hand, Carrel et al.,53 Lazaar et al.,45 and Yin et al.55 used strategies to improve involvement in moderate-to-vigorous, noncompetitive physical activities without any strategies for improving food habits. Carrel and colleagues53 made use of lifestyle-focused, fitness-oriented gymnasium activities such as walking, cycling, and snowshoeing during physical education class, where 42 minutes of the 44-minute class period were used for these activities. Competitive games were de-emphasized. Lazaar et al.45 added 1 hour of additional physical activity program held after class (additional to usual physical education classes) twice a
week, which included traditional games with different intensity, duration, and various combinations of exercises being used. Yin and colleagues55 initiated an after-school physical activity program with a duration of 80 minutes that provided skills training for 20 minutes, continuous moderate-to-vigorous physical activities for 40 minutes, and calisthenics for 10 minutes. Various tag games and ball games were used to decrease the monotony of the program. This program also included 40 minutes of academic enhancement and provided a healthy snack before exercise. The duration of the implementation of the intervention programs varied, from less than 6 months to greater than 2 years. Table 2 highlights the effects on the different measures of overweight collected by the primary studies included in the meta-analysis (the three follow-up studies41– 43 are not included).
Table 2. Summary of results on the effects of the measurement of overweight Prevalence of overweight/obesity
Study 57
Harrell (1996) Gorthmaker (1999)10 Robinson (1999)51 Grey (2004)58 Carrel (2005)53 Coleman (2005)47 Yin (2005)55 Spiegel (2006)44 Kain (2004)54 Jiang (2007)50 Huang (2007)56 James (2004)46 Lazaar (2007)45 Graf (2005)52 Manois (1999)48 Manois (2002)49
BMI
Waist girth
Waist–hip ratio
Triceps skinfold thickness
NS
% body fat NS
2
2
Less increase NS NS NS NS
Less increase NS
2 Less increase 2 NS 2 NS but near 2 2
2
Less increase
Less increase 2
NS NS
NS
2 2 2 2 NS
NS 2
2 2
2 NS
NS NS 2
Note: Shaded boxes indicate that outcome measure was not used in the study.
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Meta-Analysis of Outcome Measures Prevalence of Overweight and Obesity Figure 2 shows the forest plot of the comparison of intervention and control arms in decreasing the number of participants who were overweight and obese. The odds of participants being overweight and obese in the combined intervention arms compared with the combined comparison arms were significantly protective (OR⫽0.74, 95% CI⫽0.60, 0.92). This highlights that the intervention arm was more effective in decreasing the number of participants who become overweight or obese. In analyzing the intervention programs regarding duration of implementation, studies that Figure 2. Comparison of school-based intervention programs versus control regarding their were applied for more than effect on the prevalence of overweight and obesity 1–2 years or those that lasted more than 2 years showed a Body Mass Index lower likelihood of participants being overweight and Figure 4 shows the results of a study in which the intervenobese, with ORs of 0.81 (95% CI⫽0.68, 0.92) and 0.59 (95% tion arm was not effective in decreasing the BMI compared CI⫽0.37, 0.94), respectively, compared with shorter-period to the control arm, using WMD (⫺0.62, 95% CI⫽⫺1.39, programs of less than 6 months. This means that the longer 0.4). Analysis of the effectiveness of the intervention prothe intervention period, the greater the decrease in likeligram in relation to the duration of its implementation hood of being overweight and obese compared to shortershowed that programs with a duration of 1–2 years had a duration intervention periods. The likelihood of being oversignificant decrease in WMD (⫺0.10, 95% CI⫽⫺0.14, weight and obese in programs held for less than 6 months ⫺0.06). was not statistically different from those who did not enroll in the intervention program. It was possible to perform a meta-analysis on the effect of Other Measures of Obesity interventions that used physical activity and classroom activThe intervention program produced a decrease in waist ities on the change in prevalence of overweight and obesity girth, compared to the control program (WMD⫽⫺1.56, (Figure 3). The reason was that among the papers that reported changes in the prevalence of BMI categories, only two used a single intervention that was either change in physical activity45 or modification in classroom activity.46 The OR of decreasing the prevalence of overweight and obesity was significant in the intervention group, with an OR of 0.73 (95% CI⫽0.55, Figure 3. Subgroup analysis of interventions using modifications in both classroom activities and physical education/physical activities 0.96). 422
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Figure 4. Comparison of the effect on the mean change in BMI due to a school-based intervention program versus control WMD, weighted mean difference
95% CI⫽⫺2.53, ⫺0.60). The intervention group had a significant decrease in percentage body fat, with a WMD of ⫺1.51 (95% CI⫽⫺2.47, ⫺0.56) compared with the control group. The effect of the intervention program on waist– hip ratio showed that the intervention group did not significantly reduce the waist– hip ratio with a WMD of ⫺0.01 (95% CI⫽⫺0.03, 0.00). However, the control group had a significantly higher mean difference in the triceps skinfold thickness, compared with November 2009
the intervention group (WMD⫽0.10, 95% CI⫽0.03, 0.16).
Long-Term Effect of the Intervention Program on BMI Only three studies41– 43 reported long-term follow-up results regarding the effectiveness of an intervention program after it had been terminated. James and colleagues41 studied the project Christchurch Obesity Am J Prev Med 2009;37(5)
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Prevention Programme in Schools 12 months and 3 years after baseline measurements. Danielzik et al.42 investigated the Keil Obesity Prevention Study 10 years after the start of the intervention, while Kafatos43 analyzed the effectiveness of the Cretan Health and Nutritional Education Programme, a Figure 5. Comparison of the long-term effect on the number of obese and overweight 6-year program, 4 years after participants due to school-based intervention programs versus controls its cessation. Figure 5 shows the longmeta-analysis is more comprehensive in terms of recency term effect of intervention programs in decreasing the and number of studies, number of outcome measures number of participants who became overweight and included, as well as coverage of both short- and long-term obese. It shows that there was no difference between effects. the intervention and control arms (OR⫽0.85, 95% This meta-analysis found that school-based intervenCI⫽0.69, 1.05). Figure 6 shows the long-term effect of tions were effective in decreasing the prevalence of the intervention programs on the mean change in BMI. overweight and obesity but not in reducing BMI in This shows that the intervention program had a signiftreatment groups in comparison to control groups. This icant WMD of ⫺0.42 (95% CI⫽⫺0.69, ⫺0.14). The 42 was different from the findings of Katz and colleagues,19 results from Danielzik and colleagues’ paper are not wherein nutrition and physical activity interventions reshown in Figure 6, as they were provided as median sulted in significant reductions in BMI compared to values. controls (SMD⫽⫺0.32, 95% CI⫽⫺0.54, ⫺0.10), when There are always concerns about the effect of sample pooling nine studies. However, the meta-analysis of size on the aggregated effect. However, it is not beKatz et al.19 did not consider the prevalence of overlieved that the study sample sizes influenced the overall weight and obesity as an outcome measure. findings, as sorting the data by effect size indicated a The effectiveness of a school-based intervention prononsystematic order of the studies (i.e., not in order of gram could be influenced by many factors that may be sample size). outside the control of the investigators. While the research design should address duration of the program and the intervention used, other factors such as Discussion the age of participants, involvement of parents, school environment/culture, and compliance with the interThis meta-analysis provided sound evidence to support vention cannot be readily controlled.52 This metaschools as favorable settings for obesity prevention in 19 analysis considered factors such as duration and type of children. Although the Katz et al. study was the most intervention by their impact on the success of the recent comparable meta-analysis, Table 3 outlines the differences between the two meta-analyses. The current intervention program.
Figure 6. Comparison of the long-term effects on the mean change in BMI due to school-based intervention programs versus controls
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Table 3. Comparison of meta-analysis with Katz19 Katz Date range 1966–October 2004 Eligibility criteria Only papers with at least 6 months of follow-up Age⫽3–18 years n⫽11 papers Papers overlapping in the two reviews James (2004)46 Robinson (1999)51 Grey (2004)58 Kain (2004)54 Paper excluded in Katz but included in Gonzales-Suarez Gorthmaker (1999)10
Statistics Measures of fatness were combined (BMI, weight, ponderosity) and reported as SMD. SMD⫽⫺0.32, 95% CI⫽⫺0.54, ⫺0.1
Tests for heterogeneity Choice of fixed or random effects model was based on the 2 test for heterogeneity (p⬍0.05). Conclusions Combination interventions are effective in achieving weight reduction in school settings. Larger effect if use family involvement
Gonzalez-Suarez 1995–2007 Short- and long-term effects Age⫽11⫹ years (preadolescent and adolescent) n⫽19 papers Katz papers ineligible for this review (based on date) Walter (1988, 1985) Tamir (1990) Lionnis (1991) Gorthmaker 1999 used dichotomous data of prevalence change in BMI, not mean change, and therefore was not eligible for inclusion in Katz. However, it was relevant for the current review. No measures of weight other than BMI were used. Katz used weight, ponderosity (kg/m3), and BMI. All these measures have a common denominator (kg), and thus using all measures is unnecessary. However, other measures of fatness were used, which were included in the studies included in the review, comprising waist, waist–hip ratio, triceps skinfold, and percentage body fat. Separate measures of obesity were reported as WMD for each measure. Choice of fixed or random effects model was based on the 2 test for heterogeneity (p⬍0.05) and the I2⬎75%. Combination interventions are effective in achieving weight reduction in school settings. Longer-term interventions were more effective than short-term interventions.
SMD, standardized mean difference; WMD, weighted mean difference
The analysis of the effectiveness of the intervention comparing the duration of the implementation of the intervention showed that programs that were implemented for more than 1 year led to a significant change in the weighted mean change in BMI, as compared with interventions that lasted less than 6 months. Logically, it follows that the longer the duration of the intervention, the more time the participants have to lose weight. Furthermore, intervention programs that are designed to prevent further weight gain combined with longitudinal growth in height and increase in lean body mass can lead to a reduction in BMI. Children, especially those who are overweight, may be able to “grow into” their weight. This result contradicts the findings of the systematic reviews of Sharma,13,14 which indicated that the effectiveness of the intervention was not necessarily linked with length of implementation. This meta-analysis found that the combination of increasing physical activity and classroom curriculum decreases the prevalence of childhood overweight and obesity significantly. However, interventions that used physical activity and classroom activities alone were not able to be analyzed separately. Watts et al.60 proposed November 2009
that prevention of childhood obesity should emphasize an increase in physical activity instead of a change in diet because of the possible adverse effects of inappropriate eating patterns that may develop in children. Similar findings came from a systematic review of Connelly and colleagues12 that included 28 trials, with 11 trials being effective and 17 trials being ineffective in reducing adiposity. A meta-analysis and systematic review by Katz et al.19 showed that nutrition and physical activity interventions resulted in significant reductions in BMI compared to a control (SMD⫽⫺0.32, 95% CI⫽⫺0.54, ⫺0.10). This meta-analysis drew a conclusion that was similar to that of Katz and colleagues’ study19: interventions that used both physical activities and classroom teachings about proper nutrition and physical activity were more effective in reducing childhood obesity compared with those that involved either physical activity or classroom teachings. It is of note that the papers that used physical activity programs deemphasized competitive sports and used lifestyle exercises such as games, swimming, sports dance, and cycling, which were recommended by Lobstein et al.59 and Parizkova et al.61 as more “usual” childhood activities. Am J Prev Med 2009;37(5)
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Meta-analysis of the follow-up studies of three intervention programs41– 43 found that there was no difference in the long-term effectiveness of the intervention compared with the control in decreasing the prevalence of overweight and obesity. However, the results from two of the follow-up studies41,43 show that the mean change in BMI was lower in the intervention group compared to the control group. This requires further research, as the small numbers of papers and the low power of the individual papers potentially constrains the accuracy of the findings. Although other measures of obesity showed a mixed response to the school-based interventions, it would seem appropriate for future studies to include more than one measure of obesity, in order to determine the true effectiveness of school-based interventions in reducing childhood overweight and obesity. More methodologically robust studies are required, with larger samples and greater power. The interventions need to be better described and should be multipronged, including dietary and physical activity intervention. Intervention programs should be of longer duration (⬎2 years) to be more effective in decreasing the prevalence of childhood obesity.
Conclusion This meta-analysis showed that long-running schoolbased interventions were effective in preventing childhood overweight and obesity. It found that combined interventions of physical activity and classroom curriculum were effective in preventing childhood overweight and obesity. The duration of the intervention was positively associated with its effectiveness. Given these results, school principals and policymakers should consider implementing school-based interventions as long-term strategies for preventing and managing childhood overweight and obesity. This, in turn, should lead to healthier and more productive adults and reduce the predicted healthcare burden worldwide that will result from obesity-related morbidity in adults. No financial disclosures were reported by the authors of this paper.
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5. Luo J, Hu FB. Time trends of obesity in pre-school children in China from 1989 to 1997. Int J Obes 2002;26:555– 8. 6. Wabitsch M. Overweight and obesity in European children: definition and diagnostic procedures, risk factors and consequence for later health outcome. Eur J Pediatr 2000;159(S):S8 –13. 7. Thorpe L, List D, Marx T, May L, Helgerson S, Frieden T. Childhood obesity in New York City elementary school students. Am J Public Health 2004;94:1496 –500. 8. Burke V, Beilin LJ, Dunbar D, Kevan M. Associations between blood pressure and overweight defined by new standards for body mass index in childhood. Prev Med 2004;38:558 – 64. 9. Donnelly JE, Jacobsen DJ, Whatley JE, et al. Nutrition and physical activity program to attenuate obesity and promote physical and metabolic fitness in elementary school children. Obes Res 1996;4:229 – 43. 10. Gortmaker S, Peterson K, Wiecha J, et al. Reducing obesity via a school based interdisciplinary intervention among youth: Planet Health. Arch Pediatr Adolesc Med 1999;153:409 –18. 11. Mo-Suwan L, Pongprapai S, Junjana C, Peutpaiboon A. Effects of a controlled trial of a school based exercise program on the obesity indexes of preschool children. Am J Clin Nutr 1998;68:1006 –111. 12. Connelly J, Duaso M, Butler G. A systematic review of controlled trials of interventions to prevent childhood obesity and overweight: a realistic synthesis of the evidence. Public Health 2007;121:510 –7. 13. Sharma M. School-based interventions for childhood and adolescent obesity. Obes Rev 2006;7:261–9. 14. Sharma M. International school-based interventions for preventing obesity in children. Obes Rev 2006;8:155– 67. 15. Doak C, Visscher T, Renders C, Seidell J. The prevention of overweight and obesity in children and adolescents: a review of interventions and programmes. Obes Rev 2006;7:111–36. 16. DeMattia L, Lemont L, Meurer L. Do interventions to limit sedentary behaviours change behaviour and reduce childhood obesity? A critical review of the literature. Obes Rev 2007;8:69 – 81. 17. The Joanna Briggs Institute. Comprehensive systematic review training program manual. Adelaide, Australia: The Joanna Briggs Institute, 2004. 18. RevMan web page. www.cc-ims.net/RevMan. 19. Katz D, O’Connell M, Njike V, Yeh MC, Nawaz H. Strategies for the prevention and control of obesity in the school setting: systematic review and meta-analysis. Int J Obes 2007;1–11. doi:10.1038/sj.ijo.0803684. 20. Suhota P, Rudolf M, Dixey R, Hill A, Barth J, Cade J. Evaluation of implementation and effect of primary school based intervention to reduce risk factors for obesity. Br Med J 2001;323:1– 4. 21. Frenn M, Malin S, Bansal N. Stage based interventions for low fat diet with middle school students. J Pediatr Nurs 2003;18(1):36 – 45. 22. Bryn Austin S, Kin J, Wiecha J, Troped P, Feldman H, Peterson K. School based overweight preventive intervention lowers incidence of disordered weight control behaviors in early adolescent girls. Arch Pediatr Adolesc Med 2007;161(9):865– 8. 23. Haerens L, Deforche B, Maes L, Cardon G, Steven V, De Bourdeaudhuij I. Evaluation of a 2 year physical activity and healthy eating intervention in middle school children. Health Educ Res 2006;21(6):911–21. 24. Gortmaker S, Cheung L, Peterson K, et al. Impact of a school based interdisciplinary intervention on diet and physical activity among urban primary school children. Arch Pediatr Adolesc Med 1999;153:975– 83. 25. Simon C, Wagner A, DiVita C, et al. Intervention centred on adolescents’ physical activity and sedentary behavior: concept and 6 months result. Int J Obes 2004;28:S96 –103. 26. Warren J, Henry C, Lightowler J, Bradshow S, Perwaiz S. Evaluation of a pilot school programme aimed at the prevention of obesity in children. Health Promot Int 2003;18(4):287–96. 27. Datar A, Sturm R. Physical education in elementary school and body mass index: evidence from the early childhood longitudinal study. Am J Public Health 2004;94(9):1501– 6. 28. Reilly J, Kelly L, Montgomery C, et al. Physical activity to prevent obesity in young children: cluster randomized controlled trial. Br Med J 2006;333L: 1041–5. 29. Resnicow K, Yaroch A, Davis A, et al. Go Girls! Results from a nutrition and physical activity program for low income, overweight African American adolescent females. Health Educ Behav 2000;27:616 –31. 30. Stolley M, Fitzgibbon M. Effects of an obesity prevention program on the eating behavior of African American mothers and daughters. Health Educ Behav 1997;24:152– 64. 31. Taylor M, Mazzone M, Wrotniak B. Outcome of an exercise and educational intervention for children who are overweight. Pediatr Phys Ther 2005;17:180 – 8.
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32. Perry C, Stone E, Parcel G, et al. School-based cardiovascular health promotion: the Child and Adolescent Trial for Cardiovascular Health (CATCH). J Sch Health 1990;60(8):406 –13. 33. Wang Y, Tussing L, Odoms-Young A, et al. Obesity prevention in low socioeconomic status urban African-American adolescents: study design and preliminary finds of the HEALTH-KIDS study. Eur J Clin Nutr 2006;60:92–103. 34. Dämon S, Dietrich S, Widhalm K. PRESTO–Prevention Study of Obesity: a project to prevent obesity during childhood and adolescence. Acta Paediatr 2005;94(S448):47. 35. Liu A, Hu X, Ma G, et al. Report on childhood obesity in China (6): evaluation of a classroom based physical activity promotion program. Biomed Environ Sci 2007;20:19 –23. 36. Flores R. Dance for health: improving fitness in African American and Hispanic adolescents. Public Health Rep 1995;110(2):189 –93. 37. Muller MJ, Asbeck I, Mast M, Langnäse K, Grund. Prevention of obesity— more than an intention. Concept and first results of the Keil Obesity Prevention Study (KOPS). Int J Obes 2001;25(S1):S66 –74. 38. Caballero B, Clay T, Davis S, et al. Pathways: a school based randomized controlled trial for the prevention of obesity in American Indian schoolchildren. Am J Clin Nutr 2003;78:1030 – 8. 39. Neumark-Sztainer D, Story M, Hannan P, Rex J. New Moves: a school based obesity prevention program for adolescent girls. Prev Med 2003;37:41–51. 40. Sahota P, Rudolf M, Dixey R, Hill A, Barth J, Cade J. Randomized controlled trial of primary school based intervention to reduce risk factors for obesity. Br Med J 2001;323:1–5. 41. James J, Thomas P, Kerr D. Preventing childhood obesity: two year follow up results from the Christchurch Obesity Prevention Programme in Schools (CHOPPS). Br Med J 2007;335:762–5. doi:10.1136/bmj.39342. 571806.55. 42. Danielzik S, Pust S, Muller M. School based interventions to prevent overweight and obesity in pre-pubertal children: process and 4 years outcome evaluation of the Keil Obesity Prevention Study (KOPS). Acta Pediatr 2007;96:19 –25. 43. Kafatos A, Manios Y, Moschandreas J, and Preventive Medicine and Nutrition Clinic University of Crete research team. Health and nutrition education in primary schools of Crete: follow-up changes in body mass index and overweight status. Eur J Clin Nutr 2005;59:1090 –2. 44. Spiegel S, Foulk D. Reducing overweight through a multidisciplinary school based intervention. Obesity 2006;14:88 –96. 45. Lazaar N, Aucouturier J, Ratel S, Rance M, Meyer M, Duche P. Effect of physical activity intervention on body composition in young children: influence of body mass index status and gender. Acta Pediatr 2007; 96:1315–20. 46. James J, Thomas P, Cavan D, Kerr D. Preventing childhood obesity by reducing consumption of carbonated drinks: cluster randomized controlled trial. Br Med J 2004;328:1237. doi:10.1136/bmj.38077.458438.EE. 47. Coleman K, Tiller C, Sanchez J, et al. Prevention of the epidemic increase in child risk of overweight in low income schools. Arch Pediatr Adolesc Med 2005;159:217–24.
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48. Manois Y, Moschandreas J, Hatzis C, Kafatos A. Evaluation of a health and nutrition education program in primary school children of Crete over a three year period. Prev Med 1999;28:149 –59. 49. Manois Y, Moschandreas J, Hatzis C, Kaftos A. Health and nutrition education in primary schools of Crete: changes in chronic disease risk factors following a 6 year intervention program. Br J Nutr 2002;88:315–24. 50. Jiang J, Xia X, Greiner T, Wu G, Lian G, Rosenqvist U. The effects of a 3-year obesity intervention in schoolchildren in Beijing. Child Care Health Dev 2007;33(5):641– 6. doi:10.1111/j.1365–2214.2007.00738.x. 51. Robinson T. Reducing children’s television viewing to prevent obesity. JAMA 1999;282:1561–7. 52. Graf C, Rosr S, Koch B, et al. Data from the StEP TWO programme showing the effect on blood pressure and different parameters for obesity in overweight and obese primary school children. Cardiol Young 2005;15:291– 8. 53. Carrel A, Clark R, Peterson S, Nemet B, Sullivan J, Allen D. Improvement of fitness, body composition, and insulin sensitivity in overweight children in a school based exercise program: a randomized controlled study. Arch Pediatr Adolesc Med 2005;159:963– 8. 54. Kain J, Uauy R, Albala, Vio F, Cerda R, Leyton B. School based obesity prevention in Chilean primary school children: methodology and evaluation of a controlled study. Int J Obes Relat Metab Disord 2004;28(4): 483–93. 55. Yin Z, Gutin B, Johnson M, et al. An environmental approach to obesity prevention in children: Medical College of Georgia Fitkid project year 1 results. Obes Res 2005;13:2153– 61. 56. Huang S, Weng K, Hsieh K, et al. Effects of a classroom based weight control intervention on cardiovascular disease in elementary school obese children. Acta Paediatr 2007;48:201– 6. 57. Harrell J, McMurray R, Bangdiwala S, Frauman A, Gansky S, Bradley C. Effects of school based intervention to reduce cardiovascular disease risk factors in elementary school children: the Cardiovascular Health in Children (CHIC) study. J Pediatr 1996;128:797– 805. 58. Grey M, Berry D, Davidson M, Galasso P, Gustafson E, Melkus G. Preliminary testing of a program to prevent type 2 diabetes among high risk youth. J School Health 2004;74(1):10 –15. 59. Lobstein R, Baur L, Uaay R. Obesity in children and young people: a crisis in public health. Obes Rev 2004;5(S1):4 – 85. 60. Watts K, Jones TW, Davis EA, Green D. Exercise training in obese children and adolescents: current concepts. Sports Med 2005;35(5):375–92. 61. Parizkova J, Maffeis C, Poskitt EME. Management through activity. In: Burniat W, Cole T, Lissau I, Poskitt EME, eds. Child and adolescent obesity: causes and consequences, prevention and management. Cambridge, UK: Cambridge University Press, 2002:307–26.
Appendix Supplementary Data Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.amepre.2009.07.012.
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This paper aims to evaluate the effectiveness of school-based programs in the prevention and management of childhood obesity.
Methods:
A comprehensive literature search was undertaken for RCTs and clinical controlled trials on school-based interventions that addressed childhood obesity, published between 1995 and 2007. The papers included for the meta-analysis were those in which ORs or standardized mean differences and their 95% CIs were reported or could be calculated from available data.
Results:
Meta-analysis showed that the odds of participants’ being overweight and obese in the school-based intervention programs compared with the control arm were significantly protective in the short term (OR⫽0.74, 95% CI⫽0.60, 0.92). Interventions that were conducted for more than 1 year had a higher OR of decreasing the prevalence of obesity. However, intervention programs were not effective in decreasing BMI compared with control treatments, with a weighted mean difference of ⫺0.62 (95% CI⫽⫺1.39, 0.14).
Conclusions: This meta-analysis showed that there was convincing evidence that school-based interventions are effective, at least short-term, in reducing the prevalence of childhood obesity. Longer-running programs were more effective than shorter programs. (Am J Prev Med 2009;37(5):418 – 427) © 2009 American Journal of Preventive Medicine
Background
C
hildhood obesity has been recognized as an increasing health problem worldwide over the past decade. In the U.S., the prevalence of overweight children aged 5–14 years rose from 15% in 1973 to 32% in 1994, while that of obesity increased from 5% in 1973 to 22% in 1994.1 Similar increases have been reported in countries such as the United Kingdom, Germany, Australia, and China.2–5 Childhood obesity has been associated with diseases in childhood such as asthma, early-onset diabetes mellitus, and childhood hypertension.6 It has also been shown that childhood obesity is a predictor of obesity during adulthood.4,7 High BMI in adulthood is strongly linked to chronic and nonreversible diseases, such as hypertension, diabetes mellitus, coronary arterial disease, occlusive cerebrovascular disease, and degenerative joint disease. ImFrom the Centre for Allied Health Evidence (Gonzalez-Suarez, Worley, Grimmer-Somers), University of South Australia, Adelaide, Australia; and University of Santo Tomas (Gonzalez-Suarez, Dones), Manila, Philippines Address correspondence and reprint requests to: Consuelo B. Gonzalez-Suarez, PhD, MD, Center for Research on Movement Science, Thomas Aquinas Research Complex, University of Santo Tomas, Espana St, Manila, Philippines 1008. E-mail: cgsuarez@ mnl.ust.edu.ph.
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portantly, a study by Burke and colleagues8 showed that being overweight between ages 14 and 19 years is associated with increased mortality after age 30 years from systemic diseases. It is therefore important to recognize and treat overweight and obesity in children. Research studies on the effectiveness of methods in controlling childhood obesity have variably tested the following individually or in combination: ●
● ● ●
change in diet (such as reducing the intake of high-density and high-caloric food and replacing it with foods that are high in fiber); decrease in sedentary behavior; increase in physical activity through enrollment in a structured physical fitness program; behavior modification.
Most research has been school-based and has been characterized by the delivery of nutritional education, promotion of decreased TV viewing and sedentary behavior through pamphlets and lectures, modification of the food being provided by school canteens, and physical activity programs.9 –11 All studies are conducted under the premise that sustainable changes in diet and physical activity will be achieved if they are carried into adulthood and will prevent obesity in later years. However, there has
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been unconvincing evidence on the effectiveness of school programs to reduce any measure of overweight and obesity in children, either short-term or long-term, from systematic reviews of the literature.12–16
Objectives This paper reports on a meta-analysis that was conducted on studies to evaluate the evidence for the effectiveness of school-based programs in the management of childhood obesity in terms of BMI, percentage of body fat, waist girth, triceps skinfold, and waist– hip ratio.
Methods Participants The review considered schoolchildren of any nationality who were of normal BMI, overweight or obese, and in preadolescent and adolescent phases, with fatness classified by an age- and gender-specific cutoff point system developed by the International Obesity Task Force or by country-specific norms. Children of normal BMI were included in the study because the study investigated both the prevention and treatment of overweight and obesity.
terms undertaken in the following databases: Ovid (MEDLINE, PsycINFO, EMBASE, EBM Reviews), Cochrane Library, CINAHL, Current Contents, BioMed Central, AustHealth, SCOPUS, TRIP (Turning Research into Practice), Science Direct, EMBASE, Health Source: Nursing/Academic Edition, AMED, PubMed, and Academic Elite. The identified keywords were as follows: Concept 1: childhood obesity, adolescent obesity, youth obesity, child obesity Concept 2: treatment or management or prevention or program The second phase was a search of the reference lists and bibliographies of all potentially relevant articles identified in Phase 1. All studies identified during the database search and search of the reference lists were assessed for relevance to the review based on information provided in the title and abstract. If considered relevant, the full text of the paper was retrieved for further analysis of whether the study met the inclusion criteria.
Methodologic Quality
The outcome measures examined in the review included BMI, waist girth, percentage body fat, and triceps skinfold. For the purpose of this meta-analysis, short-term outcomes were considered to be those measured immediately after completion of the intervention, while long-term outcomes were those that were measured at least 6 months after completion of the intervention program.
The studies were appraised by two independent reviewers for methodologic quality before inclusion in the meta-analysis. Should any disagreement have arisen between the reviewers, it would have been resolved by adjudication of a third reviewer. Inter-rater reliability was tested using Cohen’s kappa coefficient. The kappa coefficient was 0.75. A quality score was set at 60% of the possible total score, which weights the findings of the review toward studies of high internal methodologic quality that are externally valid. Methodologic quality was assessed using the JBI (Joanna Briggs Institute) Critical Appraisal of Evidence Effectiveness tool (see Appendix A, available online at www.ajpm-online.net).17 This critical appraisal tool has been endorsed by the JBI, and use of this tool is mandated for any systematic reviews to be undertaken using the JBI framework. Because the interventions included classroom activities and improvement or addition of activities in physical education class, blinding of the participants to treatment allocation was improbable. Keeping this in mind, the highest possible score that a study could obtain was 10 (as Question 2 was removed from the critical appraisal tool for this review). Question 2 asked, Were participants blinded to treatment allocation? A score of 6 and above was determined as appropriate methodologic quality, and thus studies of six or more would be included in the review (representing 60% of the possible total score). No priority was given to completion of any specific criteria in the methodologic quality checklist.
Study Design
Data Extraction and Analysis
The meta-analysis included only those RCTs and clinical controlled trials that had high methodologic critical appraisal scores (more than 60% of the possible criteria met).
Data were extracted using the data extraction tool developed by the JBI.17 Data extracted included sample size, subject age and gender, intervention(s) description and control group(s) description, outcome measures, length of intervention, confounders, comorbidities, short- and long-term results, significance, relevance, and generalizability. The papers included in the meta-analysis were also those in which odds ratio (ORs) or standardized mean differences (SMDs) and their 95% confidence interval (CI) were reported or could be calculated from available data. Where applicable, results from comparable studies were pooled in a statistical analysis using the Review Manager software (RevMan) from the Cochrane Collaboration.18 ORs were used in data that were in
Intervention The interventions that were considered for inclusion in the review were any deliberate approach to ● ● ● ●
increase physical activity, improve dietary behaviors, modify poor exercise or dietary behaviors, or a combination of the above approaches.
However, the interventions were relevant to this review only if they were delivered in a school-based program, with the aim of addressing overweight and obesity in the target population.
Outcome Measures
Language and Date Restrictions Searches included publications in English only, published between 1995 and 2007. This time frame was established because of a large worldwide increase over the past decade in combating childhood obesity.
Search Strategy of Literature Sources A two-step search strategy was employed. The first phase was a comprehensive search using identified keywords and index
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binary form (prevalence of overweight and obesity) while weighted mean differences (WMDs) were used in data that were in continuous form (BMI, waist circumference, waist– hip ratio, and triceps skinfold). Each measure of fatness was analyzed separately. Where studies reported mean changes in outcome measures from baseline to post-intervention for each group, data were entered in RevMan with the corresponding number of participants and ␦s (pooled SD). For studies that reported both pre- and post-intervention values but without mean change, the change was computed by subtracting the baseline measurement from the post-intervention measurement. The ␦s (pooled SD) was estimated using the equation19
␦s⫽兹[(␦pre 2⫹␦post 2) ⁄ 2]. When SE was reported, the pooled SD was computed using ␦⫽SE 公n. Significance in CIs for ORs is identified by the 95% CI not encompassing 1, and for mean differences, not encompassing 0. To obtain the WMD with 95% CI for both the treatment and control groups, a random effects model was used when heterogeneity was present (p⬍0.05) and if the computed I 2 was more than 75%; otherwise, the fixed effects model was used.
Results The search identified 41 papers based on their title for possible inclusion in the review, of which 19 papers were included in the meta-analysis (Figure 1).
Excluded Studies Fifteen papers were excluded because they did not meet the inclusion criteria. Six papers20 –25 had no outcomes for measures assessing overweight and obesity; four papers11,26 –28 included preschoolers as the participants; two papers29,30 had interventions that were community-based; one paper31 had a family-centered intervention; one paper32 had height and weight self-reported by participants; and another paper33 had only preliminary findings of baseline measurements. Four further studies34 –37 were excluded because of poor methodologic
quality. Three papers38 – 40 were excluded because their ORs or SMDs and 95% CIs were not reported or could not be calculated from available data. Of the 19 papers included, three were follow-up studies41– 43 (see Figure 1 and Appendix B, available online at www.ajpm-online. net, for full details of included studies).
Outcome Measures Body mass index was reported in all included papers. This was either used as a cutoff point for overweight and obesity to test the effectiveness of the intervention in decreasing the prevalence of overweight in the sample population or by obtaining the change in mean BMI. The other measures of obesity used in the included studies were waist girth; triceps skinfold thickness; percentage body fat, which was measured by bioelectric impedance, dual energy absorptiometry, or by the sum of skinfolds; waist– hip ratio; and subscapular skinfold thickness (Table 1).10,42–58 Most papers used multiple measures of obesity, except for the studies by Jiang et al.50 and Kafatos et al.,43 which used BMI only. Only the studies by James et al.,46 Huang et al.,56 and Manois et al.49 reported mean change with SD and did not require additional computation. For the study by Manois and colleagues,49 the percentage change in triceps skinfold required computation. All other papers required computation by the researchers, as described in the Methods section.
Interventions The interventions reported in the included studies were generally designed to decrease overweight by increasing physical activity, to decrease participation in sedentary activities, and to decrease intake of food high in fat and sugar content. This was achieved by having classroom lessons that emphasized the reduction of consumption of high-fat, sugary foods; increase in intake of fruits and vegetables; and the importance of increasing physical activity. In addition to this, physical education classes were modified so that a larger percentage of the time period was spent in moderate-to-vigorous physical activity.
Strategies
Figure 1. CONSORT diagram of papers included in the meta-analysis
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Most of the studies used multipronged intervention strategies. In the study reported by Grey and coworkers,58 the intervention was improved by telephone calls that focused on enhancing self-image. Modifications in the school environment, such as providing healthy foods in schools canteens, were incorporated in the management strategy reported by Kain et al.54 Parental involvement was included in the interventions reported by Kain and colleagues54 and Danielzik et al.42 Single interventions were reported in five studies,45,46,51,53,55 reflecting modification in classroom curriculum or variations in physical education or physical
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Table 1. Outcome measures available for meta-analysis Study 42
Danielzik (2007) Kafatos (2005)43 Spiegel (2006)44 Lazaar (2007)45 Gorthmaker (1999)10 James (2004)46 James (2007)41 Coleman (2005)47 Manois (1999, 2002)48,49 Jiang (2007)50 Robinson (1999)51 Graf (2005)52 Carrel (2005)53 Kain (2004)54 Yin (2005)55 Huang (2007)56 Harrel (1996)57 Grey (2004)58
Prevalence
BMI change
Waist girth
Body fat
Waist–hip ratio
Triceps skinfold
— — X X X X — X X X — — — — — — — —
X X — — X X X X X X X X X X X X X X
— — — — — X X — — — X X
— — — — — — — — — — — X X — X X X —
— — — — — — — — — — X X — — — — — —
X — — — — — — — X — X — — X — — — —
X X — — X
activities held in schools. Robinson51 provided lessons that emphasized reduction of hours spent in TV viewing, while James and colleagues46 allotted a 1-hour session each term that emphasized decrease in intake of carbonated drinks and the importance of water. On the other hand, Carrel et al.,53 Lazaar et al.,45 and Yin et al.55 used strategies to improve involvement in moderate-to-vigorous, noncompetitive physical activities without any strategies for improving food habits. Carrel and colleagues53 made use of lifestyle-focused, fitness-oriented gymnasium activities such as walking, cycling, and snowshoeing during physical education class, where 42 minutes of the 44-minute class period were used for these activities. Competitive games were de-emphasized. Lazaar et al.45 added 1 hour of additional physical activity program held after class (additional to usual physical education classes) twice a
week, which included traditional games with different intensity, duration, and various combinations of exercises being used. Yin and colleagues55 initiated an after-school physical activity program with a duration of 80 minutes that provided skills training for 20 minutes, continuous moderate-to-vigorous physical activities for 40 minutes, and calisthenics for 10 minutes. Various tag games and ball games were used to decrease the monotony of the program. This program also included 40 minutes of academic enhancement and provided a healthy snack before exercise. The duration of the implementation of the intervention programs varied, from less than 6 months to greater than 2 years. Table 2 highlights the effects on the different measures of overweight collected by the primary studies included in the meta-analysis (the three follow-up studies41– 43 are not included).
Table 2. Summary of results on the effects of the measurement of overweight Prevalence of overweight/obesity
Study 57
Harrell (1996) Gorthmaker (1999)10 Robinson (1999)51 Grey (2004)58 Carrel (2005)53 Coleman (2005)47 Yin (2005)55 Spiegel (2006)44 Kain (2004)54 Jiang (2007)50 Huang (2007)56 James (2004)46 Lazaar (2007)45 Graf (2005)52 Manois (1999)48 Manois (2002)49
BMI
Waist girth
Waist–hip ratio
Triceps skinfold thickness
NS
% body fat NS
2
2
Less increase NS NS NS NS
Less increase NS
2 Less increase 2 NS 2 NS but near 2 2
2
Less increase
Less increase 2
NS NS
NS
2 2 2 2 NS
NS 2
2 2
2 NS
NS NS 2
Note: Shaded boxes indicate that outcome measure was not used in the study.
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Meta-Analysis of Outcome Measures Prevalence of Overweight and Obesity Figure 2 shows the forest plot of the comparison of intervention and control arms in decreasing the number of participants who were overweight and obese. The odds of participants being overweight and obese in the combined intervention arms compared with the combined comparison arms were significantly protective (OR⫽0.74, 95% CI⫽0.60, 0.92). This highlights that the intervention arm was more effective in decreasing the number of participants who become overweight or obese. In analyzing the intervention programs regarding duration of implementation, studies that Figure 2. Comparison of school-based intervention programs versus control regarding their were applied for more than effect on the prevalence of overweight and obesity 1–2 years or those that lasted more than 2 years showed a Body Mass Index lower likelihood of participants being overweight and Figure 4 shows the results of a study in which the intervenobese, with ORs of 0.81 (95% CI⫽0.68, 0.92) and 0.59 (95% tion arm was not effective in decreasing the BMI compared CI⫽0.37, 0.94), respectively, compared with shorter-period to the control arm, using WMD (⫺0.62, 95% CI⫽⫺1.39, programs of less than 6 months. This means that the longer 0.4). Analysis of the effectiveness of the intervention prothe intervention period, the greater the decrease in likeligram in relation to the duration of its implementation hood of being overweight and obese compared to shortershowed that programs with a duration of 1–2 years had a duration intervention periods. The likelihood of being oversignificant decrease in WMD (⫺0.10, 95% CI⫽⫺0.14, weight and obese in programs held for less than 6 months ⫺0.06). was not statistically different from those who did not enroll in the intervention program. It was possible to perform a meta-analysis on the effect of Other Measures of Obesity interventions that used physical activity and classroom activThe intervention program produced a decrease in waist ities on the change in prevalence of overweight and obesity girth, compared to the control program (WMD⫽⫺1.56, (Figure 3). The reason was that among the papers that reported changes in the prevalence of BMI categories, only two used a single intervention that was either change in physical activity45 or modification in classroom activity.46 The OR of decreasing the prevalence of overweight and obesity was significant in the intervention group, with an OR of 0.73 (95% CI⫽0.55, Figure 3. Subgroup analysis of interventions using modifications in both classroom activities and physical education/physical activities 0.96). 422
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Figure 4. Comparison of the effect on the mean change in BMI due to a school-based intervention program versus control WMD, weighted mean difference
95% CI⫽⫺2.53, ⫺0.60). The intervention group had a significant decrease in percentage body fat, with a WMD of ⫺1.51 (95% CI⫽⫺2.47, ⫺0.56) compared with the control group. The effect of the intervention program on waist– hip ratio showed that the intervention group did not significantly reduce the waist– hip ratio with a WMD of ⫺0.01 (95% CI⫽⫺0.03, 0.00). However, the control group had a significantly higher mean difference in the triceps skinfold thickness, compared with November 2009
the intervention group (WMD⫽0.10, 95% CI⫽0.03, 0.16).
Long-Term Effect of the Intervention Program on BMI Only three studies41– 43 reported long-term follow-up results regarding the effectiveness of an intervention program after it had been terminated. James and colleagues41 studied the project Christchurch Obesity Am J Prev Med 2009;37(5)
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Prevention Programme in Schools 12 months and 3 years after baseline measurements. Danielzik et al.42 investigated the Keil Obesity Prevention Study 10 years after the start of the intervention, while Kafatos43 analyzed the effectiveness of the Cretan Health and Nutritional Education Programme, a Figure 5. Comparison of the long-term effect on the number of obese and overweight 6-year program, 4 years after participants due to school-based intervention programs versus controls its cessation. Figure 5 shows the longmeta-analysis is more comprehensive in terms of recency term effect of intervention programs in decreasing the and number of studies, number of outcome measures number of participants who became overweight and included, as well as coverage of both short- and long-term obese. It shows that there was no difference between effects. the intervention and control arms (OR⫽0.85, 95% This meta-analysis found that school-based intervenCI⫽0.69, 1.05). Figure 6 shows the long-term effect of tions were effective in decreasing the prevalence of the intervention programs on the mean change in BMI. overweight and obesity but not in reducing BMI in This shows that the intervention program had a signiftreatment groups in comparison to control groups. This icant WMD of ⫺0.42 (95% CI⫽⫺0.69, ⫺0.14). The 42 was different from the findings of Katz and colleagues,19 results from Danielzik and colleagues’ paper are not wherein nutrition and physical activity interventions reshown in Figure 6, as they were provided as median sulted in significant reductions in BMI compared to values. controls (SMD⫽⫺0.32, 95% CI⫽⫺0.54, ⫺0.10), when There are always concerns about the effect of sample pooling nine studies. However, the meta-analysis of size on the aggregated effect. However, it is not beKatz et al.19 did not consider the prevalence of overlieved that the study sample sizes influenced the overall weight and obesity as an outcome measure. findings, as sorting the data by effect size indicated a The effectiveness of a school-based intervention prononsystematic order of the studies (i.e., not in order of gram could be influenced by many factors that may be sample size). outside the control of the investigators. While the research design should address duration of the program and the intervention used, other factors such as Discussion the age of participants, involvement of parents, school environment/culture, and compliance with the interThis meta-analysis provided sound evidence to support vention cannot be readily controlled.52 This metaschools as favorable settings for obesity prevention in 19 analysis considered factors such as duration and type of children. Although the Katz et al. study was the most intervention by their impact on the success of the recent comparable meta-analysis, Table 3 outlines the differences between the two meta-analyses. The current intervention program.
Figure 6. Comparison of the long-term effects on the mean change in BMI due to school-based intervention programs versus controls
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Table 3. Comparison of meta-analysis with Katz19 Katz Date range 1966–October 2004 Eligibility criteria Only papers with at least 6 months of follow-up Age⫽3–18 years n⫽11 papers Papers overlapping in the two reviews James (2004)46 Robinson (1999)51 Grey (2004)58 Kain (2004)54 Paper excluded in Katz but included in Gonzales-Suarez Gorthmaker (1999)10
Statistics Measures of fatness were combined (BMI, weight, ponderosity) and reported as SMD. SMD⫽⫺0.32, 95% CI⫽⫺0.54, ⫺0.1
Tests for heterogeneity Choice of fixed or random effects model was based on the 2 test for heterogeneity (p⬍0.05). Conclusions Combination interventions are effective in achieving weight reduction in school settings. Larger effect if use family involvement
Gonzalez-Suarez 1995–2007 Short- and long-term effects Age⫽11⫹ years (preadolescent and adolescent) n⫽19 papers Katz papers ineligible for this review (based on date) Walter (1988, 1985) Tamir (1990) Lionnis (1991) Gorthmaker 1999 used dichotomous data of prevalence change in BMI, not mean change, and therefore was not eligible for inclusion in Katz. However, it was relevant for the current review. No measures of weight other than BMI were used. Katz used weight, ponderosity (kg/m3), and BMI. All these measures have a common denominator (kg), and thus using all measures is unnecessary. However, other measures of fatness were used, which were included in the studies included in the review, comprising waist, waist–hip ratio, triceps skinfold, and percentage body fat. Separate measures of obesity were reported as WMD for each measure. Choice of fixed or random effects model was based on the 2 test for heterogeneity (p⬍0.05) and the I2⬎75%. Combination interventions are effective in achieving weight reduction in school settings. Longer-term interventions were more effective than short-term interventions.
SMD, standardized mean difference; WMD, weighted mean difference
The analysis of the effectiveness of the intervention comparing the duration of the implementation of the intervention showed that programs that were implemented for more than 1 year led to a significant change in the weighted mean change in BMI, as compared with interventions that lasted less than 6 months. Logically, it follows that the longer the duration of the intervention, the more time the participants have to lose weight. Furthermore, intervention programs that are designed to prevent further weight gain combined with longitudinal growth in height and increase in lean body mass can lead to a reduction in BMI. Children, especially those who are overweight, may be able to “grow into” their weight. This result contradicts the findings of the systematic reviews of Sharma,13,14 which indicated that the effectiveness of the intervention was not necessarily linked with length of implementation. This meta-analysis found that the combination of increasing physical activity and classroom curriculum decreases the prevalence of childhood overweight and obesity significantly. However, interventions that used physical activity and classroom activities alone were not able to be analyzed separately. Watts et al.60 proposed November 2009
that prevention of childhood obesity should emphasize an increase in physical activity instead of a change in diet because of the possible adverse effects of inappropriate eating patterns that may develop in children. Similar findings came from a systematic review of Connelly and colleagues12 that included 28 trials, with 11 trials being effective and 17 trials being ineffective in reducing adiposity. A meta-analysis and systematic review by Katz et al.19 showed that nutrition and physical activity interventions resulted in significant reductions in BMI compared to a control (SMD⫽⫺0.32, 95% CI⫽⫺0.54, ⫺0.10). This meta-analysis drew a conclusion that was similar to that of Katz and colleagues’ study19: interventions that used both physical activities and classroom teachings about proper nutrition and physical activity were more effective in reducing childhood obesity compared with those that involved either physical activity or classroom teachings. It is of note that the papers that used physical activity programs deemphasized competitive sports and used lifestyle exercises such as games, swimming, sports dance, and cycling, which were recommended by Lobstein et al.59 and Parizkova et al.61 as more “usual” childhood activities. Am J Prev Med 2009;37(5)
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Meta-analysis of the follow-up studies of three intervention programs41– 43 found that there was no difference in the long-term effectiveness of the intervention compared with the control in decreasing the prevalence of overweight and obesity. However, the results from two of the follow-up studies41,43 show that the mean change in BMI was lower in the intervention group compared to the control group. This requires further research, as the small numbers of papers and the low power of the individual papers potentially constrains the accuracy of the findings. Although other measures of obesity showed a mixed response to the school-based interventions, it would seem appropriate for future studies to include more than one measure of obesity, in order to determine the true effectiveness of school-based interventions in reducing childhood overweight and obesity. More methodologically robust studies are required, with larger samples and greater power. The interventions need to be better described and should be multipronged, including dietary and physical activity intervention. Intervention programs should be of longer duration (⬎2 years) to be more effective in decreasing the prevalence of childhood obesity.
Conclusion This meta-analysis showed that long-running schoolbased interventions were effective in preventing childhood overweight and obesity. It found that combined interventions of physical activity and classroom curriculum were effective in preventing childhood overweight and obesity. The duration of the intervention was positively associated with its effectiveness. Given these results, school principals and policymakers should consider implementing school-based interventions as long-term strategies for preventing and managing childhood overweight and obesity. This, in turn, should lead to healthier and more productive adults and reduce the predicted healthcare burden worldwide that will result from obesity-related morbidity in adults. No financial disclosures were reported by the authors of this paper.
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Appendix Supplementary Data Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.amepre.2009.07.012.
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