Study design and flow of participants through the trial.
A, Mean change in waist circumference (between-group difference, −1.60 cm [95% CI, −2.28 to −0.91]; P < .001). B, Mean change in BMI z score (between-group difference, 0.01 [95% CI, −0.03 to 0.06]; P = .55). Error bars indicate standard errors of the mean. Comparisons were adjusted for baseline values and intention-to-treat analysis.
aP < .05.
Error bars indicate standard errors of the mean. Comparisons were adjusted for baseline values and intention-to-treat analysis.aP < .05.
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Santos RG, Durksen A, Rabbani R, et al. Effectiveness of Peer-Based Healthy Living Lesson Plans on Anthropometric Measures and Physical Activity in Elementary School Students: A Cluster Randomized Trial. JAMA Pediatr. 2014;168(4):330–337. doi:10.1001/jamapediatrics.2013.3688
Schools are considered an attractive setting to promote healthy living behaviors in children, but previous school-based interventions aimed at preventing weight gain in children have yielded mixed results. Novel school-based approaches are needed to modify healthy living behaviors and attenuate weight gain in children.
To assess the effectiveness of a peer-led healthy living program called Healthy Buddies on weight gain and its determinants when disseminated at the provincial level to elementary school students.
Design, Setting, and Participants
Cluster-randomized effectiveness trial performed during the 2009-2010 school year. Baseline and follow-up measurements were made in October 2009 and May 2010, respectively. The study was performed in 19 elementary schools in Manitoba, Canada, and included 647 elementary school students aged 6 to 12 years (48% girls).
Schools were randomized to receive regular curriculum or Healthy Buddies lesson plans. Lesson plans were delivered by older (9- to 12-year-old) elementary school students to the younger (6- to 8-year-old) peers and targeted 3 components of health: physical activity, healthy eating, and self-esteem and body image.
Main Outcomes and Measures
The primary outcome measures were the change in waist circumference and body mass index z score. Secondary outcomes included physical activity (steps per day), cardiorespiratory fitness, self-efficacy, healthy living knowledge, and self-reported dietary intake.
At baseline, 36% of children were overweight or obese and 11% achieved the recommended 13 500 steps per day. Intention-to-treat analyses showed that waist circumference declined significantly in the intervention group relative to controls: −1.60 cm (−2.28 to −0.91; P < .001). Reductions in waist circumference were particularly significant for children who were overweight or obese or attending First Nations schools. No difference in body mass index z score was observed between groups. Self-efficacy, healthy living knowledge, and dietary intake significantly improved in younger peers who received the intervention compared with students from control schools. No differences were observed in daily step counts or cardiorespiratory fitness between the groups.
Conclusions and Relevance
The implementation of Healthy Buddies lesson plans delivered by older peers within an elementary school setting is an effective method for attenuating increases in central adiposity and improving knowledge of healthy living behaviors among elementary school students. Improvements were achieved with parallel improvements in diet quality, self-efficacy, and knowledge of healthy living.
Schools are an attractive setting to promote healthy living behaviors in children.1 Unfortunately, most teacher-led school-based interventions have been ineffective at reducing body weight in children.2 In contrast to traditional school-based interventions, peer mentoring is an attractive strategy for eliciting behavior change in children.3,4 A recent peer-led program called “Healthy Buddies” targeted healthy eating, physical activity, and self-efficacy among elementary school students.4 Healthy Buddies consists of a set of healthy living lesson plans taught to older students (grades 4-6), who then act as mentors, transferring the knowledge to younger students in the school (kindergarten through grade 3). A pilot trial of Healthy Buddies in a Canadian school showed attenuated weight gain and reduced blood pressure in mentors and mentees respectively, relative to students receiving a standard curriculum.4 A similar peer-based strategy reduced obesity rates among African American adolescents paired with young adults.5 Although these data appear promising, the studies used quasi-experimental designs without randomization and were not disseminated at the state or provincial level. The present study was designed to overcome these limitations by using a cluster-randomized effectiveness trial to test the hypothesis that a school-based, peer-led healthy living program would reduce adiposity and increase physical activity among children.
In the spring of 2009, 60 elementary schools in Manitoba indicated an interest in piloting Healthy Buddies lesson plans in the 2009-2010 academic calendar year. Participating schools met the eligibility criteria by (1) being within the provincial jurisdiction, (2) having a minimum of 200 students per school, and (3) offering grades 1 through 6. Among these schools, 20 were randomly selected to participate and randomly assigned to receive the Healthy Buddies curriculum (10 schools: 5 urban and 5 rural) or to serve as a waiting list control group receiving a regular curriculum (10 schools: 4 rural and 6 urban).
Schools were randomized in a computer-generated random selection process and blocked to ensure equal representation from rural and First Nations (ie, indigenous) schools in both intervention and control arms. Randomization was performed by an investigator who was not involved in data collection. Figure 1 displays the distribution of schools and participant flow through the study. The intervention lasted approximately 10 months (1 school year). Within the intervention schools, administrators assigned 2 teachers, 1 from a grade 4 to 6 classroom and 1 from a kindergarten to grade 3 classroom, to deliver the lesson plans to their classrooms. Parents provided written consent for participation, and children assented to study protocols. Children were excluded if consent was not received or if they had a condition that limited participation in physical activity. The study protocol was approved by the Biomedical Research Ethics Board at the University of Manitoba in accordance with the Declaration of Helsinki.
The details of the intervention have been described elsewhere.4 Teachers delivering the Healthy Buddies lesson plans attended a 2-day training seminar at the beginning of the 2009-2010 academic school year. The program content focused on physical activity, promoting healthy foods, and having a healthy body image using the slogans: “Go Move!” (activity), “Go Fuel!” (nutrition), and “Go Feel Good!” (body image). Twenty-one lessons were provided to teachers to be delivered during the school year to older students.
In schools randomized to the intervention, an older class was paired with a younger class. Each week, the older students received a 45-minute healthy living lesson from their classroom teacher. Later that week, the older students acted as peer mentors, teaching a 30-minute lesson to their younger “buddies.” The “Go Move!” aspect included two 30-minute structured aerobic fitness sessions per week, called fitness loops, with the student pairs. Students were encouraged to complete the fitness loops at a vigorous intensity using perceived exertion scales. The “Go Fuel!” component included lessons about distinguishing nutritious from unhealthy (nutrient-poor, energy-rich) foods and beverages. As part of the “Go Feel Good!” component, students were taught to value themselves and classmates based on individual traits rather than peer influence. The peer-led model facilitated social skills, self-esteem, and social responsibility. A more comprehensive description of the Healthy Buddies program can be obtained at http://www.healthybuddies.ca.
The primary outcome measures were body mass index (BMI) z score and waist circumference. Outcome measures were collected at the beginning (September 2009) and end (May 2010) of the academic calendar year during day visits to each school. Research assistants were blinded to study assignment. The BMI (calculated as weight in kilograms divided by height in meters squared, with height measured in centimeters) was measured in duplicate with a portable floor scale (Seca 869) and stadiometer (Seca 217). Raw BMI values and age in months were used to calculate BMI z scores based on Centers for Disease Control and Prevention growth charts. Waist circumference (in centimeters) was measured by using a flexible tape at the level of the iliac crest using the method established by McCarthy et al.6
Secondary outcome measures included physical activity, cardiorespiratory fitness, self-efficacy, healthy living knowledge, and self-reported dietary intake. Healthy living questions were extracted from questionnaires that are considered valid and reliable for children within this age range.7,8 The test-retest reliability of the healthy living questionnaire is excellent for youth within this age range (r = 0.7-0.9).4 The subscale of self-efficacy has been validated for youth aged 8 to 12 years.9 Physical activity was assessed objectively by using daily logs of step counts obtained from a waist-mounted pedometer (StepsCount SC-01) worn for 7 days.10 Students were asked to wear the pedometer on the right hip for all waking hours of the day. Teachers collected daily step counts from children and logged them into a data collection sheet.11
Cardiorespiratory fitness was determined from a Léger 20-m shuttle run in the older students only.12,13 This is a continuous, graded shuttle run test to exhaustion in which fitness is estimated from the final stage (ie, running velocity) achieved.13 The pace started at 5 km/h and increased 0.5 km/h every minute until students were unable to maintain the pace, as determined by a research assistant. A second research assistant paced students through the protocol to ensure that the test was paced properly.
Standardized questionnaires were previously developed by the Healthy Buddies research group at the British Columbia Children’s Hospital, Vancouver, to assess self-esteem and healthy living knowledge and behaviors.4 The instrument consisted of 65 questions for younger and 165 questions for older students. Questions were grouped into 6 categories: (1) self-efficacy, (2) knowledge of healthy eating, (3) knowledge of healthy activities, (4) current physical activity levels, (5) current eating patterns, and (6) body image. Teachers participating in the intervention also completed a questionnaire about perceived strengths and weaknesses associated with implementation and delivery of the program. This was included in the study design to facilitate adoption of Healthy Buddies at other sites in the province if the program successfully attenuated weight gain or increased physical activity.
Data are presented as means and 95% confidence intervals unless otherwise stated. Primary comparisons of outcome measures are reported assuming randomization occurred at the individual level. Differences in changes in primary and secondary outcome variables between intervention and control groups were tested using a mixed model approach, which was used to control variation at the level of the individual. We also calculated the intraclass correlation to compare variation between school classes as a fraction of the total variance. All comparisons were adjusted for baseline differences in residence (rural vs urban), age, and sex. All analyses were adjusted for random effect of student and within-school clustering using a compound symmetry structure for the within-student correlations. All data were analyzed in an intention-to-treat analysis, with the last value carried forward.
The treatment effect (or effect size) reported was calculated as the mean gains scored difference (MGSD) = [mean difference (intervention) – mean difference (control)]/pooled SD, wherewhere r is the pre-post correlation (Spearman correlation of the preintervention vs postintervention variable). The 95% CIs were calculated as [MGSD ± 1.96 × standard error of the MGSD], where
We based our sample size calculation on a predefined ratio of 1:1 between intervention and control schools, assuming 2 classes per school with a classroom size of 25 to 30 children. A sample size of 10 clusters (schools) per group and 19 individuals per cluster provided 80% power to detect a difference of 1.38 cm in waist circumference between groups, assuming an SD of 3.0 cm and an intracluster correlation of 0.30. Assuming an attrition rate of 10% to 15% and accounting for the multiple secondary outcomes, we recruited 647 children within 40 classrooms. This sample size provided adequate power to detect a difference of 0.008 cm between groups, assuming an SD of 0.03 cm and an intracluster correlation of 0.04. All data were analyzed using SAS, version 9.2, software (SAS Institute Inc), and results were considered statistically significant at α < .05.
In the fall of 2009, a total of 647 students within 38 classrooms in 19 schools were enrolled into the trial. Ten schools (340 students) were randomized to the intervention arm, and 10 (347 students) to the control arm; 1 school (40 students) withdrew from the study after being randomized to the control group. The flow of participants through the study is presented in Figure 1. Overall, 49% of students attended rural schools, 48% were girls, 36% were overweight or obese, and 11% achieved a minimum of 13 500 steps per day. Baseline participant demographics are presented in Table 1. In the spring of 2010, a total of 584 students from 19 schools repeated the measurements. Reasons for not returning included (1) moving to a different school, (2) withdrawing from school, and (3) being absent during the week of data collection. No differences in outcome measures were noted between completers and noncompleters.
Groupwise differences in the change in the primary outcome measures are presented in Figure 2. Compared with students in the control group, students exposed to the intervention had a significant reduction in waist circumference (−2.00 [95% CI, −2.48 to −1.51] vs −0.40 [−0.89 to 0.09] cm; P < .001). Changes in BMI z score did not differ between the intervention and control groups (0.00 [95% CI, −0.03 to 0.03] vs −0.01 [−0.04 to 0.02]; P = .55). In subgroup analyses, the reduction in waist circumference remained significant in the younger students (ie, buddies) and in the older mentors (Table 2 and Figure 3). In additional subgroup analyses, the effect of the intervention was significantly greater among overweight and obese youth relative to the healthy-weight youth in both younger peers and older mentors (Table 2).
No differences in physical activity were observed between groups in the younger peers. However, among older students, those who received the intervention displayed a reduction in average daily step counts compared with students in the control group (Table 2). At baseline, the knowledge of healthy eating and behavior was similar in older and younger students (Table 3 and Table 4). Among the younger students, the Healthy Buddies lesson plans led to significant improvements in knowledge of healthy eating and physical activity, self-reported food and drink intake, and self-esteem compared with students in the control group (P < .01 for all variables) (Table 3). These improvements were not observed in the older students (Table 4).
This cluster-randomized effectiveness trial of peer-based mentoring led to a reduction in waist circumference in elementary school students compared with students receiving a standard curriculum. Healthy Buddies also improved self-efficacy and knowledge of healthy eating among younger elementary school students who learned about healthy living from their older peers. The results of this study suggest that the Healthy Buddies lesson plans have the potential to prevent central weight gain, improve self-efficacy, and enhance healthy living knowledge and behavior among elementary school students when disseminated on a broad scale.
During the past 2 decades, numerous school-based randomized trials have tested the effects of modified curricula, with mixed results.14,15 A meta-analysis of school-based physical activity trials revealed limited effects on BMI among school-aged children.2 Landmark school-based trials16,17 found no significant effects of modified curriculum and environmental changes in food provision on measures of weight. However, more recent trials demonstrated that intensive interventions have positive effects on BMI z score or waist circumference.18-20 The effects we observed in the present trial are similar to those seen in those earlier trials (mean decrease in waist circumference, approximately 1.5 cm) and were observed without any changes in school environment (eg, food services) or additional programming (eg, after-school activities), suggesting that the positive effects may be attributed to either the novel curriculum or the peer mentoring approach.
Experimental trials of healthy living behaviors typically focus on youth who are overweight or obese.15 A systematic review of trials for obesity treatment approaches in youth suggest an expected effect size of −0.25 to −0.09 for the change in BMI z score in trials lasting less than 12 months. The effect size we observed for the change in waist circumference appears small (−0.12; 95% CI, −0.15 to −0.10) but was greater than expected (equivalent Cohen d = (−0.36; 95% CI, −0.51 to −0.20), even though it was observed in a cohort of mostly healthy-weight children. Because this was an effectiveness trial that did not specifically target overweight children, a reduction in waist circumference of approximately 1.5 cm relative to the expected age-related increase is quite robust at the population level. The reduction of central obesity is particularly important because increased visceral adiposity in youth is associated with a clustering of cardiometabolic risk factors in youth21-23 and its reduction with decreased cardiometabolic risk.24-26
Observational and experimental studies in youth have demonstrated that higher levels of moderate to vigorous physical activity are associated with lower visceral adiposity.25,27,28 This intervention’s lack of effect on measures of activity and fitness may be attributed to the timing of data collection. Previous studies have demonstrated substantial seasonal variation in physical activity patterns among youth living in northern climates.29 Previously reported peer-led strategies that effectively reduced body weight in adolescents demonstrated increased physical activity patterns measured objectively with accelerometers.5 In the absence of a change in physical activity or fitness levels, the reduction in waist circumference observed after the Healthy Buddies program may therefore be attributed to changes in dietary behavior. Using a modified food frequency questionnaire, younger students reported more frequent consumption of fruits and vegetables combined with reduced consumption of sweetened beverages and sweets. Because these children rely on parents for dietary choices, the data imply that messages provided by the Healthy Buddies lesson plans were transferred to the home environment. Transfer of knowledge from school-based behavior education to the home environment has been documented elsewhere30 but would need to be confirmed in follow-up studies.
One key secondary outcome observed in this trial was the improvement in self-efficacy among children exposed to the intervention. Self-efficacy is linked to several healthy behaviors in youth, including fruit consumption, physical activity, condom use, and avoidance of substance abuse.31-34 Very few school-based interventions have explicitly measured changes in self-efficacy despite significant evidence that self-efficacy is a robust predictor of health behaviors in youth. One school-based intervention to reduce diabetes risk factors successfully increased self-efficacy among aboriginal Canadian children,35 and others have demonstrated limited effects of healthy living programs on measures of self-efficacy, including the original Healthy Buddies pilot study.4 It is possible that improvements in self-efficacy facilitate the adoption of healthy living behaviors and increase the likelihood of achieving weight loss among youth. Future studies are needed to determine the importance of improved self-efficacy as a mediating factor for successful weight change after lifestyle interventions in children.
This study has several strengths and weaknesses. The primary strength was the use of a cluster-randomized design. The intervention itself (ie, classroom-based peer mentoring) prohibited randomization at the level of the student. The results from the current experimental design support previous quasi-experimental results.4,5 A second strength was the inclusion of schools from rural and First Nations communities in Manitoba. These communities display higher rates of obesity, sedentary behavior, and chronic diseases in youth.36,37 In the present study, rates of obesity were approximately 80% higher in the rural and First Nations schools, and these students achieved approximately 1000 fewer steps daily. The effects of the intervention on waist circumference were nearly double in First Nations compared with non–First Nations children (treatment effect, −2.5 cm [95% CI, −4.2 to −0.8] vs −1.3 cm [−2.0 to −0.6]). The importance of a culturally appropriate program has been demonstrated in previous trials delivered in indigenous populations.17,38 A culturally appropriate revision of Healthy Buddies has been developed and may be helpful in amplifying these already positive outcomes of the program in First Nations communities. Finally, adopting an effectiveness model for delivering the intervention (ie, teaching, training, and support provided by the province, not the research team) enhances the likelihood of knowledge translation at the regional or provincial level.
Randomization at the level of the school was a potential limitation. This introduces the risk of school-level factors that could confound results because factors among children could cluster at the level of the school or community, altering the intervention. However, intraclass correlation values for each outcome variable were small, suggesting that school-to-school variance was only a small portion of the overall variance. The implementation was limited to 2 classrooms within each school and was delivered for only 1 year. The long-term effects of widespread implementation of the program remain unclear.
In conclusion, the Healthy Buddies lesson plans were effective at reducing central adiposity among elementary school students in Manitoba, particularly children who were younger, overweight or obese, or First Nations. The lesson plans enhanced several determinants of healthy living, including self-efficacy, knowledge of healthy living, and self-reported healthy living behaviors among younger students. These positive effects, coupled with perceived effectiveness and positive support from teachers involved in the program, suggest that the Healthy Buddies lesson plans are a viable and effective option for addressing childhood obesity and increasing healthy living knowledge within elementary schools.
Accepted for Publication: July 11, 2013.
Corresponding Author: Jonathan M. McGavock, PhD, Department of Pediatrics and Child Health, Faculty of Medicine, University of Manitoba, 510A JBRC, Manitoba Institute of Child Health, 715 McDermot Ave, Winnipeg, MB R3E 3P4, Canada (email@example.com).
Published Online: February 10, 2014. doi:10.1001/jamapediatrics.2013.3688.
Author Contributions: Dr McGavock and Ms Durksen had full access to all the data in the study, and Dr McGavock takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Santos, Chanoine, Lamboo Miln, Mayer, McGavock.
Acquisition of data: Santos, Durksen, Lamboo Miln, McGavock.
Analysis and interpretation of data: Santos, Durksen, Rabbani, Mayer, McGavock.
Drafting of the manuscript: Santos, Durksen, Lamboo Miln, McGavock.
Critical revision of the manuscript for important intellectual content: Santos, Durksen, Rabbani, Chanoine, Mayer, McGavock.
Statistical analysis: Santos, Durksen, Rabbani, McGavock.
Obtained funding: Santos, Lamboo Miln.
Administrative, technical, and material support: Santos, Durksen, Lamboo Miln, Mayer, McGavock.
Supervision: Santos, Chanoine, McGavock.
Conflict of Interest Disclosures: Dr McGavock reports having received operating grants and/or salary awards from the Canadian Diabetes Association, the Canadian Institute of Health Research, the Cosmopolitan Foundation of Canada, and the Lawson Foundation and currently holding the Robert Wallace Cameron Chair in evidence-based child health. No other disclosures were reported.
Funding/Support: The Government of Manitoba provided funding and support for the pilot intervention (Manitoba Healthy Living) and its randomized evaluation (Healthy Child Manitoba Office).
Role of the Sponsor: The funding agency, the Province of Manitoba, helped in the design of the study, enrolling schools to participate and training teachers, but it had no role in the collection of data, statistical analyses, or interpretation of findings or in the preparation, review, or approval of the manuscript.
Disclaimer: The results and conclusions are those of the authors, and no official endorsement by the Government of Manitoba is intended or should be inferred.
Additional Contributions: We thank the participating students, teachers, administrators, and schools for accommodating our research team during the evaluation component of the trial. We also acknowledge the Government of Manitoba (Healthy Child Manitoba Office, Department of Healthy Living and Seniors, Department of Education and Advanced Learning) for its role in designing and conducting the study, with special thanks to Laura Morrison, Brian Hatherly, Tina Moody, and Keith Paterson. We also thank Andrea MacIntosh, Jackie Dumontet, Brandy Wicklow, and Paul McArthur for help with data collection and Dan Chateau for providing guidance with the statistical analyses. No financial compensation was received for any of these services.
Correction: This article was corrected on November 26, 2014, to fix minor statistical errors and the misspelling of an author’s last name.