Introduction

Scientific background

Obesity is considered to be one of the greatest challenges facing public health in the 21st century. Currently, one-fifth of boys and girls in England start school overweight or obese, and one-third of children leave primary school (aged 11 years) overweight or obese.1 Childhood obesity is strongly associated with socioeconomic status, with children from the least affluent decile being twice as likely to be obese as children from the most affluent decile.2 Childhood obesity tracks into adulthood; a recent systematic review3 reported that obese children are five times more likely than non-obese children to be obese as adults, and that 80% of obese adolescents were still obese in adulthood.

School-based obesity preventative interventions have the potential to reach a large number of children and families across the socioeconomic spectrum, and schools provide the organisational, social and communication structures to educate children and parents about healthy lifestyles. Systematic reviews of school-based interventions to prevent obesity and/or increase physical activity and reduce sedentary behaviours show, at best, moderate evidence of effectiveness, with the majority of studies conducted in the USA.4 Several methodological shortcomings have also been identified, such as differential loss to follow-up, not having sufficient statistical power to detect clinically meaningful differences between groups, particularly on adiposity outcomes, and short-term follow-up.5,6

Evidence for the effectiveness of school-based obesity prevention programmes

In 2012, Khambalia et al.7 examined the quality of evidence and findings from existing systematic reviews and meta-analyses of school-based programmes in the control and prevention of childhood obesity published between 1990 and 2010. Eight reviews and 112 studies were examined in total, with the most recent literature search conducted in 2008. All eight reviews acknowledged that the studies they included had heterogeneous designs, outcomes and ages of participants. The reviews were judged for their quality, and five were considered to be high quality according to their prespecified criteria.

These five reviews included three meta-analyses: Cook-Cottone et al.,8 which examined study factors and effect sizes in obesity prevention programmes in 6- to 12-year-olds; Gonzalez-Suarez et al.,9 which focused on the management of obesity in 11- to 18-year-olds; and Katz,10 which determined the effectiveness of school-based strategies for both obesity prevention and obesity management in 3- to 18-year-olds. The other two reviews were qualitative systematic reviews: Brown and Summerbell,11 which assessed the effectiveness of prevention programmes focusing on changing dietary intake and/or physical activity levels in 5- to 18-year-olds; and Kropski et al.,12 which provided a focused evaluation of the quality and results of long-term obesity prevention programmes in 2- to 19-year-olds.

Despite the heterogeneity of studies included in these reviews, the authors concluded that there was evidence to recommend that school-based obesity prevention programmes include both diet and physical activity components, involve the child’s family and be of longer duration. However, they did suggest that, given no one single intervention will fit all school populations, further high-quality research needs to focus on identifying specific programme characteristics and approaches predictive of success.

Wang et al.4 is the most recent systematic review and meta-analysis of childhood obesity prevention programmes. Of the 139 intervention studies identified, 115 (83%) were located in the primary school, of which 37 were school-based only. These studies assessed the effect of a combined diet and physical activity intervention on weight-related outcomes. The approaches included intensive classroom physical activity lessons led by trained teachers, moderate to vigorous physical activity sessions, nutrition and education materials, and promoting and providing a healthy diet. There was weak evidence that these approaches were effective at reducing body mass index (BMI), BMI standard deviation score (SDS), prevalence of obesity and overweight, percentage body fat, waist circumference and skinfold thickness. Intervention studies that reported a significant effect tended to be of long duration (between 52 and 156 weeks), with the longer-term programmes having the greatest effect. A further 28 studies were school-based with a home component (e.g. family homework lessons, training and information sheets for parents, nutrition programme for children and family). These studies provided moderate evidence of effectiveness, with half reporting statistically significant beneficial intervention effects. However, in all studies, a range of adiposity measures was used and there was high study heterogeneity in terms of setting, design, sample size, characteristics, intervention approach and length of follow-up, which makes cross-comparisons challenging. The review was unable to identify specific programme characteristics and approaches predictive of success or to explore the comparative effectiveness of specific intervention approaches (e.g. educational interventions vs. environmental intervention).

Since the publication of the above reviews, a number of additional evaluations of school-based interventions13–16 have been published involving children of a similar age to those in the Health Lifestyles Programme (HeLP) study. However, evidence of effectiveness in changing behaviours and/or weight status of children continues to be inconsistent and the content of the intervention varies greatly between studies.

In 2010, The Healthy Study Group13 published its findings from a 3-year cluster randomised controlled trial (RCT) of a multicomponent programme addressing risk factors for diabetes among American children whose race or ethnic group and socioeconomic status placed them at high risk of obesity and type 2 diabetes mellitus (T2DM). The intervention consisted of four integrated components: (1) nutrition, (2) physical activity, (3) behavioural knowledge and skills, and (4) communications and social marketing. No significant group differences were observed in the prevalence of overweight and obesity (primary outcome), but children in the intervention schools had a greater reduction in the secondary outcome of BMI SDS (–0.01 vs. –0.05; p = 0.04) at 3-year follow-up.

In 2011, Jansen et al.15 published their findings from an 8-month cluster RCT of a school-based intervention to reduce overweight and improve fitness in 6- to 12-year-old primary school children in a multiethnic, low-income, inner-city neighbourhood in Rotterdam, Netherlands. This was a multicomponent programme based on behavioural and ecological models, involving physical education sessions delivered by a specialist physical education teacher, additional sport and play activities outside school hours, and an educational programme. Significant positive intervention effects were found in terms of the percentage of overweight children, waist circumference and 20-minute shuttle run among those aged 6–9 years. The prevalence of overweight in 6 to 8-year-olds increased by 4.3% in the control group and by 1.3% in the intervention group. No significant effects were found for BMI for 9- to 12-year-olds.

In 2014, the results of the Active for Life-year 5 (AFLY5)16 study, a UK primary school-based cluster RCT aimed at increasing physical activity, reducing sedentary behaviours and increasing fruit and vegetable consumption in 9- to 10-year-old children, were published. No differences were observed between the intervention and control groups in the three primary outcomes outlined above. The intervention was effective for three out of nine secondary outcomes after multiple testing was taken into account: self-reported time spent in screen viewing at the weekend, self-reported servings of snacks per day and servings of high-energy drinks per day were all reduced. The intervention was an adaptation of the American school-based intervention Planet Health,17 consisting of 16 lessons (delivered by the class teacher) and 10 pieces of homework in which the children were encouraged to work with their parents.

Grydeland et al.14 assessed the effect of a 20-month cluster RCT of a school-based intervention trial on the BMI of 11-year-old children in Norway. The intervention took a multilevel approach including collaboration with school principals and teachers, school health services and parent committees. School teachers were the key in delivering the intervention components, which included lessons, fact sheets for parents, meetings and awareness raising of leisure time activities. There was no significant effect of the intervention overall, although significant effects were found for both BMI (p = 0.024) and BMI SDS (p = 0.003) in girls. Furthermore, children of higher-educated parents seemed to benefit more from the intervention, highlighting the need to develop interventions that do not widen the health inequalities that already exist between children from different socioeconomic groups.

Rationale for HeLP

We began work to design, pilot and then fully evaluate a school-based obesity prevention programme in primary schools in 2006. Our aim was to create a novel programme of activities using an intervention mapping approach18 and to follow the UK Medical Research Council’s (MRC) framework for the development and evaluation of complex interventions.19 The intervention mapping approach combines theoretical and stakeholder perspectives, empirical evidence and new research to assess and develop a potential set of possible solutions for a particular problem, rather than defining a practice or research agenda around a specific theory. We therefore searched the literature for appropriate systematic reviews of school-based obesity prevention programmes and carried out extensive stakeholder consultation with practitioners (teachers, head teachers and drama specialists), local policy-makers (director of public health and the public health policy lead), public health commissioners and the local healthy schools team, in order to understand the school, education and public health context at that time. The overarching aim of the research was to develop a school-based intervention, assess its feasibility and complete pilot work before we sought funding to run the full-scale effectiveness trial, were that deemed appropriate.20

Around the time of our initial research, the Brown and Summerbell review11 concluded that interventions that increase activity and reduce sedentary behaviours may help children to maintain a healthy weight, although the results were short term and inconsistent. Their conclusions were that a combined approach was likely to be more effective in preventing children becoming overweight in the long term.

We wanted to incorporate these recommendations into our programme and address the methodological limitations reported in other trials, such as insufficient statistical power; biased recruitment from, and retention of, more affluent schools, children and families; short follow-up periods; and high levels of attrition. Thus, a crucial focus in developing HeLP was to promote the engagement of schools, children and their families throughout the intervention, as we believed this to be essential for behaviour change to occur. In line with the World Health Organization’s Health Promoting Schools framework,21 we aimed to develop activities that were compatible with the existing school curriculum and promote messages in a manner that could have an impact on the wider school culture, as well as specific behaviours of children and their families. First and foremost, we sought to build supportive and trusting relationships with teachers, children and their families by employing people with specific skills and competencies to deliver the intervention.

We developed an initial phase of the intervention to create a receptive context for the programme and utilised engaging delivery methods to try to increase school, child and family engagement with the programme. Previous research into preventing childhood obesity has found that it can be difficult to engage parents in order to affect change within the family;22,23 thus, we believed that the delivery methods needed to be sufficiently dynamic, creative and empowering to motivate the children to talk about the activities at home with their parents and encourage parents to come into the school to attend key events. This thinking led us to explore the use of interactive drama, as it had shown promise in promoting positive attitudes towards a number of health behaviours24 and was a means of delivering a range of behaviour change techniques in manner that could engage the children.

The development of the intervention was guided by the information, motivation and behavioural skills (IMB) model25 and intervention activities were ordered to enable support and sustain behaviour change in accordance with the health action process model.26

Between 2006 and 2008, we worked with 8- to 11-year-old children in one local primary school to assess a range of delivery methods for key objectives identified in the intervention mapping process. We then went on to refine the newly developed intervention based on feedback from teachers, children and parents, and carried out a feasibility study (examining before-and-after intervention changes in the same children) in a second primary school from a more economically deprived ward of Exeter, Devon. In the feasibility study we focused solely on children aged 9–10 years, as our early work demonstrated that this age group was more receptive to the messages and, crucially, engaged their families to the greatest extent.27 Teachers also informed us that the Year 5 curriculum had the flexibility to deliver the healthy lifestyles week, whereas in Year 6 there was pressure to focus on Standard Assessment Tests (SATs). Based on qualitative data from teachers and head teachers in the piloting stages, the intervention was extended to add activities at the beginning of Year 6. Teachers felt that this would not have an impact SATs teaching and was important in further motivating the children to change behaviours. Minor refinements were also made to the education lessons and the drama scripts to enhance delivery and continuity. In 2008 we carried out an exploratory RCT [funded by the National Institute for Health Research (NIHR) Research for Patient Benefit programme] with 202 children aged 9–10 years in four schools to assess ‘proof of concept’ and the feasibility of running a cluster RCT of HeLP. The trial design and the intervention were feasible and acceptable to schools, children and their families. At 18 months, compared with children in the control schools, children in the intervention schools consumed fewer energy-dense snacks and more healthy snacks, had less negative food markers and more positive food markers, had lower mean television/screen time and spent more time doing moderate to vigorous physical activity every day.28 Children in the intervention group had lower average anthropometric measures at 18 and 24 months than children in the control group, with larger differences at 24 months than at 18 months for all measures.28

Funding for the definitive trial was awarded in March 2012 and the trial began in September 2012. None of the schools that were involved in the feasibility and pilot work were included in the definitive trial presented in this monograph.

Rationale for our study design

The HeLP study was designed to address some of the methodological weaknesses in previous school-based RCTs to prevent obesity. Schools have been highlighted as providing a captive audience with the potential to access children across the socioeconomic spectrum; however, few studies took a relational approach to both the intervention and the trial design, whereby the building of relationships with all participants to enhance engagement with the programme and the trial was a key focus in recruitment, data collection, and intervention design and delivery.

Specifically, the design of the HeLP study ensured that (1) baseline measurements were collected before schools (and children) were allocated to the intervention or the control group; (2) a standardised objective measure with a significant follow-up time was utilised to assess obesity prevention (BMI SDS at 24 months); (3) an objective measure of physical activity, with evidence of high compliance, was used29 (GeneActiv activity monitor; www.activinsights.com); (4) half of the schools had ≥ 19% of children eligible for free school meals (the national average at the time of the trial) to ensure that the results were generalisable across the socioeconomic spectrum; and (5) loss to follow-up was minimised by creating detailed standard operating procedures for the collection of all measures at each time point, with a focus on enhancing positive relationships with teachers, children and parents.

During intervention delivery we ensured that (1) delivery personnel had the necessary skills and competencies to build relationships; (2) there was one key contact person per school who co-ordinated the research hand delivery (the HeLP co-ordinator); (3) the delivery methods used were suitably engaging and dynamic for the target group, so that the children would be motivated to take the messages home and initiate discussion with their family; (4) the intervention used strategies to enhance identification with, and ownership of, the healthy lifestyle messages and enabled children to explore possible solutions and propose changes in preparation for real-life situations; (5) information and guidance on promoting healthy eating and physical activity went home to parents throughout the intervention period; and (6) parents were involved in setting goals with their child.

The intervention aimed to change behaviours both inside and outside the school environment; these measurements were concerned with behaviours across the week, including weekends. We aimed to capture physical activity data across the whole week for children at baseline and at 18-month follow-up. To support this aim, we used wrist-worn activity monitors (the GeneActiv accelerometer), as feasibility studies had demonstrated high rates of compliance with this monitor in this age group.30 We took account of the clustered nature of the trial design in the sample size calculation and analysis, and examined the effect of the intervention 6 months (18 months post baseline) and 12 months (24 months post baseline) after its completion in order to examine whether or not any observed effects of the intervention were sustained (see the published trial protocol31).

Aim and objectives

The aim of this cluster RCT was to determine the effectiveness and cost-effectiveness of HeLP in preventing overweight and obesity in children.

Our objectives were:

1. to assess the effectiveness of HeLP in children aged 9–10 years by comparing between intervention and control schools:
   1. BMI SDS at 24 months (primary outcome)
   2. BMI SDS at 18 months
   3. waist circumference SDS at 18 and 24 months
   4. percentage body fat SDS at 18 and 24 months
   5. proportion of children classified as underweight, overweight and obese at 18 and 24 months
   6. physical activity (average time spent per day in sedentary, light, moderate, moderate to vigorous and vigorous activity) and average weekly volume of physical activity in milligravity (mg) units at 18 months
   7. food intake (number of energy-dense snacks, healthy snacks, negative and positive food markers) at 18 months.
2. to estimate the costs associated with the delivery of the HeLP intervention and its cost-effectiveness versus usual practice
3. to conduct a mixed-methods process evaluation and mediational analysis to explore the way the programme worked (i.e. how it was delivered, taken up and experienced, and the possible mediators of change).