Good nutrition is vital to all human beings and adequately nourished people enjoy optimal growth, health and well-being(1). In recent years, there has been a growing concern about the diet and nutrition of young people with the recognition that health promotion from an early stage of life has a major impact on health and well-being during childhood and beyond(2). Studies indicate that good nutrition is especially important during the first years of life, since these are crucial years for normal physical and mental development. In addition, healthy eating habits in childhood not only help to prevent undernutrition, growth retardation and acute child nutrition problems, but also chronic, long-term health problems such as obesity, CHD, type 2 diabetes and stroke(Reference Nicklas3–Reference Greenstone5).
Research suggests that nutrition promotion is an accessible and effective tool in developing healthy nutrition-related practice and dietary habits in youth(Reference Inchley, Todd and Bryce6). Further, the adolescents who benefit from nutrition promotion can act as change agents by spreading the messages to a large segment of the population(Reference Massey-Stokes7). Fortunately, the importance of early learning of nutrition-related knowledge, attitudes and behaviours has long been recognized(Reference Pérez-Rodrigo and Aranceta8, Reference Weichselbaum and Buttriss9). When it comes to nutrition promotion among young people, studies show that schools can play a major role in dietary change. Evidence indicates that when children go to school, parental influence on diet decreases and food provided in schools and the influence of peers become more important(Reference Moore, Paisley and Dennehy10). Also, the school food environment is increasingly recognized as having a significant influence over children's eating behaviours because of the amount of time spent at school and the large percentage of food intake consumed while at school(Reference Derry11). An additional potential benefit of school nutrition promotion is that by improving the nutrition and health of schoolchildren, their educational performance and learning may be enhanced(Reference Naidoo, Coopoo and Lambert12). A consensus is emerging within research and stakeholder communities that action at the school level must be a priority. Such action can create a supportive environment that enables children to make healthy food choices that, ultimately, will reduce future morbidity and mortality associated with overweight and obesity(Reference Nicklas3, Reference Lytle, Seifert and Greenstein13–Reference MacLellan, Taylor and Freeze16).
Since the mid-1990s a whole-school approach, embodied by the health-promoting school (HPS) model, is increasingly being endorsed as an effective way to promote nutrition and health in the school setting(Reference Lee17, Reference Rowe, Stewart and Somerset18). This holistic approach is underpinned by Bronfenbrenner's ecological theory(Reference Bronfenbrenner19, Reference Bronfenbrenner20) and has been strongly supported by the WHO(21). In addition to promoting adoption of a curriculum in which health is specifically integrated, it recognizes the significance of school-based health policies, links with health services and partnerships between the school, the family and community(22, Reference Patterson, Sun and Stewart23). Schools have the opportunity to teach young people about food and nutrition and can demonstrate the importance of a balanced diet for future health by providing healthy choices in the school canteen and by working in partnership with parents and the wider community(Reference Bowker, Crosswaite and Hickman24).
While recent reviews evaluate either the process of nutrition interventions(Reference O'Dea and Maloney25, Reference Bartrina and Pérez-Rodrigo26) or the outcome of nutrition programmes(Reference Sjöström and Stockley27), relatively few reviews include both these two parts(Reference Woolfe and Stockley28). Even though some reviews involve both process and outcome evaluations of the intervention, they usually only focus on a specific aspect of nutrition promotion, such as nutrition policy(Reference McKenna29), breakfast(Reference Kothe and Mullan30) or fruit and vegetable consumption(Reference Helen31, Reference Klepp, Pérez-Rodrigo and De Bourdeaudhuij32). Further, few reviews focus on school-based nutrition programmes that have used a fully comprehensive or holistic HPS approach(Reference Pérez-Rodrigo and Aranceta8, Reference Ramanathan, Allison and Faulkner33). The current paper provides a systematic review of the evaluation of both the implementation and effectiveness of nutrition promotion programmes involving a wide range of nutritional aspects and using the HPS approach, either adopted in full or adopted partially. The objectives of the study are to evaluate the implementation and effectiveness of school-based nutrition promotion programmes using the HPS approach, to indicate areas where further research is needed and also to make recommendations for practice in this field, if research findings permit.
Experimental methods
Literature search
The retrieval of published studies for the present review included a structured search in the following electronic databases: CINAHL, Cochrane Library, Health Reference Center, Informit Search, MEDLINE, ProQuest, PsycINFO, PubMed, ScienceDirect, Scopus, Social Services Abstracts and Web of Science, published before 30 September 2011. No language restrictions were applied. The search strategy was designed to be inclusive and focused on two key elements: nutrition and health-promoting school. In addition, reference lists of all retrieved articles were screened for potentially eligible articles.
Study selection
To be included in the present review, studies needed to meet the following three criteria.
1. They had to be controlled studies, or before-and-after studies, evaluating school-based interventions on nutrition involving health-promoting activities in all or one or two of the following three areas:
(a) the school ethos and/or environment, such as school policy;
(b) the curriculum, specifically the nutrition curriculum;
(c) the family and/or community;
and demonstrate active participation by the school.
2. They had to provide information about the components and delivery of the intervention.
3. They had to report all evaluated outcomes.
There were no restrictions on study duration, follow-up period, control condition or who delivered the intervention.
To identify the relevant studies, the reviewers reviewed all titles and abstracts generated from the searches. Articles were rejected on initial screening only if the reviewers could determine from the title and abstract that the article did not meet the inclusion criteria. If abstracts were not available or unable to provide sufficient exclusion information, the entire article was retrieved to screen the full text. At the screening stage, all previously screened studies were again re-checked against the eligibility of inclusion criteria.
Quality assessment
A standardized quality assessment tool, the Effective Public Health Practice Project Quality Assessment Tool (EPHPP Tool) for Quantitative Studies 2003, was used to appraise the methodological rigor of the included studies(Reference Van Cauwenberghe, Maes and Spittaels34). The six criteria included for quality assessments were:
1. selection bias (i.e. ‘are the individuals selected to participate in the study likely to be representative of the target population?’);
2. study design (i.e. ‘was the study described as randomized?’);
3. confounding (i.e. ‘were there important differences between groups prior to the intervention?’);
4. blinding (i.e. ‘were the study participants aware of the research question?’);
5. data collection methods (i.e. ‘were data collection tools shown to be valid and reliable?’); withdrawals and drop-outs (i.e. ‘were withdrawals and drop-outs reported in terms of number and/or reasons per group?’).
6. withdrawals and drop-outs (i.e. ‘were withdrawals and drop-outs reported in terms of number and/or reasons per group?’).
Each criterion was rated as strong, moderate or weak, and then summed to obtain an overall score for each study. Studies with at least four criteria rated as strong and with no criteria rated as weak were given an overall rating of ‘strong’. Those studies receiving fewer than four strong ratings and only one weak rating were given an overall rating of ‘moderate’, and those studies with two or more criteria rated as weak were given an overall study rating of ‘weak’. It should be noted that as blinding is not possible for health promotion programmes, papers do not report this aspect and are not marked as weak rating in this regard.
Data extraction
To review the characteristics of the included studies, the reviewers extracted detailed information into a summary table. Data extraction included study and intervention characteristics as well as main outcomes. The study characteristics included specifics about the aims, participants and sample size, study design and outcomes. The intervention characteristics included specifics about the intervention components.
Data synthesis
A qualitative synthesis is presented. This details both the evidence presented regarding the implementation of the various nutrition interventions and also the evidence regarding the effectiveness of the selected interventions. The implementation of nutrition intervention was assessed from three aspects: (i) degree of intervention implementation; (ii) participation; and (iii) satisfaction. The effectiveness of nutrition intervention was assessed from three aspects as well: (i) participants’ knowledge; (ii) participants’ attitudes and skills; and (iii) participants’ behaviours.
Results
Literature search
The evidence available to support using the HPS approach to school-based nutrition promotion was limited, but promising. The search identified 402 articles relevant to HPS and nutrition and left 372 records after duplicates were removed. Two hundred and sixty-eight articles were deemed to be irrelevant, forty-five articles were reviews, thirty-two articles were cross-sectional surveys and twenty-seven were evaluation articles with a focus on nutrition promotion programmes. Of the twenty-seven evaluation articles, two articles were excluded as they did not provide information about the components and delivery of the intervention and six articles were excluded as they did not report all evaluated outcomes. Of the nineteen included articles(Reference Shi-Chang, Xin-Wei and Shui-Yang35–Reference Morgan, Warren and Lubans53), three articles involved interventions on nutrition policy only, six articles referred to interventions on nutrition education only and ten articles involved interventions using a comprehensive or holistic HPS approach (Fig. 1). The authors, aims, sample size, design, duration and strategies of interventions and main outcomes for each of these included studies are summarized in Table 1.
Fig. 1 Flowchart for the selection of articles on health-promoting schools and health promotion in schools on nutrition
Table 1 A summary of the aims, design and major outcomes of the nineteen studies considered in the current review
HPS, health-promoting school; CT, controlled trial; RCT, randomized controlled trial; PSE, Personal and Social Education; SES, socio-economic status.
Range and scope
The research fields ranged from breakfast eating habits and knowledge, consumption of healthier foods (fruits, vegetables and snacks) and drinks (water), knowledge and attitudes towards nutrition, food classification and hygiene to eating disorders. The minimum intervention period was 1 week and the maximum intervention period was 2 years.
Methodological quality
The results of the quality assessment are presented in Table 2. Only five of the nineteen studies achieved an overall rating as strong, five were rated as moderate and nine were rated as weak. All studies had some methodological weaknesses and none of the included studies fulfilled all the necessary quality criteria. Seven of the studies were adequately powered randomized controlled trials, five were controlled trials and seven were before-and-after comparisons. No studies were blinded and all participants in eight studies were aware of the research questions.
Table 2 Methodological quality of the reviewed studies ranked according to the EPHPP Tool
EPHPP Tool, Effective Public Health Practice Project Quality Assessment Tool for Quantitative Studies 2003; NR, not reported.
*Overall rating: strong = at least four criteria rated as strong and with no criteria rated as weak; moderate = fewer than four criteria rated as strong and only one criterion rated as weak; weak = two or more criteria rated as weak.
Evidence on implementation of nutrition intervention
All included studies described their intervention components and only six of these articles reported on a process evaluation. Of these six articles, three used quantitative methods, two used qualitative method and one used both quantitative and qualitative methods.
Degree of intervention implementation
School environment and ethos
School policies and climate. The intervention schools established policies that placed a high priority on health and nutrition promotion and increased their emphasis on collaboration among students, teachers and other school staff(Reference Shi-Chang, Xin-Wei and Shui-Yang35–Reference Young40), such as operating a breakfast club(Reference Shemilt, Harvey and Shepstone41) or creating a traffic light nutrition tool(Reference Ellis and Ellis42).
School facilities. Studies found that physical and operational improvements were made to intervention schools’ kitchens and dining areas(Reference Parker and Fox38), cooking equipment, healthy foods and clean drinking water were provided(Reference Shi-Chang, Xin-Wei and Shui-Yang35, Reference Young40, Reference Vereecken, Huybrechts and van43), and quality of the lunches and food safety had improved(Reference Radcliffe, Ogden and Welsh36, Reference Mullally, Taylor and Kuhle44).
School health services. In one study, all of the intervention schools initiated regular physical examinations for students and teachers and began to keep files with students’ health records(Reference Shi-Chang, Xin-Wei and Shui-Yang35).
Staff training. Training sessions and newsletters were provided for principals, teachers and cafeteria staff(Reference Vereecken, Huybrechts and van43).
Curriculum
In general, the curriculum strategies included: (i) classes with an increased focus on health and nutrition; (ii) adoption of a unit on body image and healthy eating; (iii) nutrition information provided to teachers to encourage increased use in curriculum; (iv) students delivering healthy eating messages in the form of poetry and skits at assembly; (v) production of a show by the school drama club, or an educational role-model story and characters; (vi) pupil competitions to produce promotional resources for healthier choices to be displayed in the school; (vii) peer-support activities; (viii) play, poster/video presentations; (ix) visiting a health promotion exhibition; and (x) various kinds of publicity materials delivery(Reference Radcliffe, Ogden and Welsh36–Reference Rana and Alvaro39, Reference Vereecken, Huybrechts and van43, Reference McVey, Tweed and Blackmore45–Reference Morgan, Warren and Lubans53).
Partnerships with parents and the wider community
In the selected articles, the interventions involving parents included: (i) a parental nutritional newsletter, pamphlets, letters and handouts; (ii) a parent education forum; (iii) involvement of parents in their children's homework assignments, education sessions, workshops, class activities and special events; and (iv) a parental version of the web-based computer tailored tool that enabled parents to get personalized feedback on their dietary intake level(Reference Radcliffe, Ogden and Welsh36–Reference Rana and Alvaro39, Reference McVey, Tweed and Blackmore45–Reference O'Brien, Roe and Reeves47). Partnerships with communities included, for example, breakfast provision(Reference Radcliffe, Ogden and Welsh36), advice and support from local nutritionists(Reference Rana and Alvaro39) and free seasonal fruit provision(Reference Laurence, Peterken and Burns46).
Degree of participation in the intervention
In summary, students and parents in different countries and schools differed significantly in their participation levels. Even though all intervention schools spent the required minimum time on their nutrition project, the content of the nutrition lessons varied between schools(Reference Wind, Bjelland and Pérez-Rodrigo37, Reference Kreisel50). In one study, less than half of people successfully completed the online food safety training programme(Reference Rana and Alvaro39); in another study, the average amount of time children used the intervention tool was 30 min compared with the recommended 50 min(Reference Kreisel50).
Degree of satisfaction with intervention
Participants’ satisfaction survey showed that most of the participants liked the group activities and were satisfied with sessions, workshops, information sheets and tools, and a majority of respondents indicated intervention activities and materials were ‘useful’, ‘very good’ or ‘very fun’(Reference Rana and Alvaro39, Reference McVey, Tweed and Blackmore45). In another study, almost all of the pupils (97 %) indicated that they wanted to join in the intervention again, while only two pupils (1·2 %) gave the grade ‘not good at all’ to the intervention(Reference Kreisel50).
Evidence of effectiveness of nutrition intervention
Diet and nutrition knowledge
Most of the studies that aimed to improve diet and nutrition knowledge had a significant effect except for two studies showing that there was no significant change in the participants’ conceptual understanding of food(Reference Bullen and Benton49) and that the levels of knowledge of healthy eating were similar in the intervention and control schools(Reference Young40). Other studies showed that knowledge about diet and nutrition improved significantly after the intervention among the target populations; the improved knowledge included knowledge on dietary guidelines and principles, nutritional deficiencies and nutrient-rich foods(Reference Shi-Chang, Xin-Wei and Shui-Yang35), healthy eating guidelines and menu planning(Reference Rana and Alvaro39), red food and green food(Reference Ellis and Ellis42), cariogenic snacking(Reference Freeman and Bunting48), energy, proteins, fats, adolescent phase, obesity, lifestyle diseases and infectious diseases(Reference Vijayapushpam, Antony and Subba Rao51) and food classification(Reference Hamilton-Ekeke and Thomas52).
Diet and nutrition attitudes and skills
Of the included studies, relatively a few of them focused on diet and nutrition attitudes and skills. The limited results showed that after intervention, more students stated that nutrition and healthy dietary intake were important(Reference Shi-Chang, Xin-Wei and Shui-Yang35, Reference Radcliffe, Ogden and Welsh36), most participants had increased their skills in healthy eating and menu planning(Reference Rana and Alvaro39), and students were more willing to taste vegetables and their ability to identify vegetables was improved(Reference Morgan, Warren and Lubans53). In addition, children were beginning to link the nutritional information they had learnt with the contents of their own lunch boxes(Reference O'Brien, Roe and Reeves47). One study showed that although the positive attitude for red food decreased, the positive feelings for green food also diminished disappointingly(Reference Ellis and Ellis42).
Diet and nutrition behaviour
The studies showed that nutrition intervention based on HPS processes had a wide range of benefits. It can increase participants’ intakes of high-fibre foods and healthier snacks(Reference Parker and Fox38, Reference Young40), their consumption of water, milk, fruit and vegetables(Reference Wind, Bjelland and Pérez-Rodrigo37, Reference Parker and Fox38, Reference Shemilt, Harvey and Shepstone41, Reference Vereecken, Huybrechts and van43, Reference Mullally, Taylor and Kuhle44, Reference Laurence, Peterken and Burns46) and also their intakes of energy and all nutrients consumed(Reference O'Brien, Roe and Reeves47). It can reduce participants’ ‘breakfast skipping’(Reference Shi-Chang, Xin-Wei and Shui-Yang35, Reference Radcliffe, Ogden and Welsh36) as well as intakes of red food, low-nutrient dense foods, fatty and cream foods(Reference Shi-Chang, Xin-Wei and Shui-Yang35, Reference Parker and Fox38, Reference Ellis and Ellis42, Reference Mullally, Taylor and Kuhle44), sweet drinks consumption(Reference Laurence, Peterken and Burns46) and eating disorders(Reference McVey, Tweed and Blackmore45). Moreover, it can help to develop hygienic habits and increase food safety behaviours(Reference Shi-Chang, Xin-Wei and Shui-Yang35). Among these studies, more than a third focused on the promotion of fruit and vegetable consumption, and only one study emphasized that the positive behaviour change (high-fibre food intake) was sustained at the end of 2 years(Reference Parker and Fox38).
Costs
Only one article provided relevant information on the cost; in that programme, each school was offered a $AUD 1500 grant to develop and implement the programme. The author commented that having external funding can be an impetus for action that supports the schools to reinforce and apply the information and skills they gain from participating in the programme(Reference Rana and Alvaro39). Another three articles mentioned funding. One complained that due to the limited funding allocated for the evaluation, the follow-up period (11 weeks) was too short to be confident of identifying effects(Reference Shemilt, Harvey and Shepstone41); the second identified the same limited extra budget for the evaluation and data collection, so the evaluation depended mainly on participants’ willingness and effort(Reference Vereecken, Huybrechts and van43). The third concluded that even with considerable input, it is difficult to achieve sustained dietary changes in the eating habits of secondary-school children(Reference Parker and Fox38). However, there was no mention of the exact amount of input.
Discussion
Childhood growth and nutrition is recognized internationally as an important area in every child's development(Reference Vereecken, Huybrechts and van43, Reference Mullally, Taylor and Kuhle44), and it is essential to promote nutrition among youth as health promotion from early stages in life has a major impact on health and well-being during childhood and in later life(Reference McVey, Tweed and Blackmore45–Reference O'Brien, Roe and Reeves47). To evaluate the implementation and effectiveness of school-based nutrition promotion programmes using the HPS approach, we conducted a systematic review of controlled trial studies and before-and-after studies. We aimed to extend previous systematic reviews on this topic, to indicate areas where further research is needed and to make recommendations for practice in this field.
It is generally recognized that due to the complex nature of eating behaviour, it is difficult to change(Reference Doak, Visscher and Renders54). On the one hand, there is no clear link between knowledge gain and behaviour changes(Reference Lynagh, Schofield and Sanson-Fisher55). For example, one study found that all of the participants were knowledgeable about healthier and unhealthier foods and drinks, but were not able to use it to modify their daily dietary choices(Reference Freeman and Bunting48). Another study concluded that while participants may gain factual knowledge, they do not develop the skills to bring about behavioural change(Reference Bullen and Benton49). On the other hand, there are real difficulties in achieving behaviour change when teachers do not possess the specialist knowledge of nutrition education, nutrition research or health promotion techniques(Reference Nutbeam56). Thus, if teachers are to deliver high-quality nutrition promotion activities and become better role models, they require greater support and adequate training in nutritional knowledge and evaluation techniques(Reference Nutbeam57). In addition, it has been recommended that single behaviours should be targeted in a comprehensive and multifaceted manner, with evidence suggesting children and their families are less likely to incorporate numerous lifestyle changes all at once, and that more targeted and simple to adopt messages may be more effective(Reference Booth and Samdal58, Reference Parsons, Stears and Thomas59).
Of all the articles reviewed, only three used qualitative methods alone. Two of the articles used qualitative data to assist in explaining inconsistencies or observed differences from analysis outcomes(Reference Shemilt, Harvey and Shepstone41, Reference Ellis and Ellis42). The other article revealed that qualitative data brought to light valuable information, such as weaknesses of the intervention tool, recommendations for how to modify the programmes and the target population's satisfaction degree towards the programmes(Reference Kreisel50). All three studies are critical and useful for identifying problems, adjusting the intervention strategies, summarizing aspects of the programme and providing valuable experiences for future programmes(Reference Ritchie, Crawford and Woodward-Lopez60–Reference Edberg, Corey and Cohen62). Further qualitative studies are required to supplement the quantitative studies in the future.
The longest intervention period lasted for 2 years, and the shortest one lasted for only 1 week. There is general agreement that the formation of healthy dietary habits is a lengthy process and restructuring is not accomplished by a few hours, or even days, of instruction; thus 1 week is clearly not long enough to produce behaviour change(Reference O'Dea and Maloney25, Reference Lynagh, Schofield and Sanson-Fisher55–Reference Nutbeam57). Other studies echoed this reservation regarding the use of nutrition interventions that are based on short exposure times. Another study found that changing children's eating behaviour is difficult due to the complex nature of their behaviours and can be particularly difficult to change using short-term interventions(Reference Morgan, Warren and Lubans53). One study suggested that future programmes around healthy eating in schools should be held over at least a year(Reference Rana and Alvaro39). This could pose problems, however, with another study finding it difficult to gather and maintain momentum in implementing strategies within a period of one school year and that it was important to develop strategies that were sustainable after the project ceased(Reference Radcliffe, Ogden and Welsh36). The evidence suggests that those who design nutrition interventions need to recognize the characteristics and patterns of social, cultural and behavioural factors within a socio-ecological perspective when exploring feasible and effective interventions for a target population(Reference Booth and Samdal58–Reference Shiner, Whitley and Van Citters61). In addition, once healthy eating habits have been cultivated it is vital to provide supportive reinforcing factors to strengthen those behaviours and to prevent healthy behaviours reverting back to unhealthier ones(Reference Edberg, Corey and Cohen62, Reference Nancy63). Intensive, comprehensive, whole-of-school interventions over a substantial period of time are required for nutrition promotion programmes.
Besides longer interventions, long-term follow-up evaluation is also essential. One article showed that there were no significant changes in school-based eating at the end of a 2-year study, although there were some positive changes in the early stage of the intervention(Reference Parker and Fox38). This is consistent with other reviews, particularly those studies that actually assessed changes in dietary intake, which found no overall effect in the long term but some effect in the short term or in population subgroups(Reference Bastian64–Reference Antonio, Kelly and Valle66). Long-term follow-up is essential if we are to determine whether nutrition interventions offer sustained benefits(Reference Smith67, Reference Coryn, Schröter and Noakes68). If lasting effects and the sustainability of nutritional interventions are significant, long-term follow-up evaluation is important.
However, both long-period interventions and long-term follow-up evaluations can be restricted by available funding(Reference Romanenko69, Reference Margetts70). One study found that having external funding or additional support and resources can empower schools to build on their intervention activities(Reference Rana and Alvaro39). Another impact of the limited research funds available was indicated by one article in which the mean follow-up data collection period was 11 weeks – dictated by the original short time span of the funding allocated for the evaluation. The authors argue that this may be too short a period to be confident of identifying effects(Reference Shemilt, Harvey and Shepstone41). Another article indicated that due to the limited budget for the evaluation of the interventions and data collection, the evaluation study depended mainly on participants’ willingness and efforts to fill in questionnaires and observation sheets(Reference Vereecken, Huybrechts and van43). Clearly, having adequate funding and necessary supports are vital to identifying the efficacy of comprehensive nutrition promotion programmes.
Conclusions
No more than twenty studies have been published in the databases interrogated to evaluate the effectiveness of school-based nutrition promotion programmes using a full or partial holistic HPS approach, although nutrition promotion in schools is very common. In terms of an assessment of methodological quality, only five of the included studies achieved an overall rating as strong. All studies included described their intervention components and six of these articles reported on process evaluation. In general HPS terms, the school environment and overall ethos were more supportive for a healthy diet after the intervention, with an associated curriculum component and engagement of parents and community. Target population (students, school staff and parents) participated in the intervention at different levels and the majority of the participants were satisfied with the intervention. Evidence indicates that nutrition promotion programmes using the HPS approach, either partially or fully, can be effective.
Implications for research
Future research should provide teachers with greater support and adequate training in nutritional knowledge and evaluation techniques to allow them to deliver high-quality nutrition promotion activities; apply a comprehensive and multifaceted manner to promote more targeted and single behaviours; and conduct more and further qualitative studies to supplement quantitative studies. In addition, longer intervention periods and long-term follow-up evaluations (both the implementation and the effectiveness of the intervention) are required for future nutrition promotion programmes as behavioural change is typically a long process and to observe lasting effects. The sustainability of nutritional interventions is worth studying in further research. Finally, having adequate funding and necessary supports are vital to nutrition promotion programmes in schools.
Acknowledgements
This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors. The authors have no conflicts of interest to declare. Ethical approval was not required for the study. The contribution of each author is as follows: D.W. carried out the literature searches and screened the initial results, assessed the methodological quality of the studies, extracted data, analysed the findings and drafted the tables and manuscript. D.S. assisted with screening the full-text articles and assessing methodological quality, provided the conceptual plan and HPS expertise and helped draft the manuscript. Both authors contributed to synthesizing the results and critical revision of the manuscript, and both approved the final version.
