Title: Towards optimal public health interventions for preventing obesity in children: a novel evidence synthesis
Funder: Department of Health and Social Care

Abstract: One in five children in England is obese at age 12. Childhood obesity is associated with poorer mental and physical health. It affects children unequally, with higher levels of obesity seen in children from more deprived areas. Obesity tends to continue into adulthood. It is known to lead to numerous diseases such as diabetes, stroke and cancer. The UK government considers obesity to be a public health priority. It aims to halve childhood obesity by 2030._x000D_ _x000D_ Over the last 30 years, many different strategies have been tried around the world to prevent childhood obesity. Which of these strategies work? For which children do they work? Under which circumstances do they work best? These are the questions we want to answer in our project. We will bring together a large number studies of different strategies. Our starting point for this will be a Cochrane Review that our team put together. Cochrane Reviews are regarded as the gold-standard of evidence about what works in health care. They are widely used to inform policy. Using this review as a starting point will be a lot more efficient than undertaking a new review._x000D_ _x000D_ At the heart of our proposal is a statistical analysis of the results of all the studies we find. We expect there to be over 200 studies, which is many more than have been analysed together before. We will use a new method to analyse these studies, called “component-based network meta-analysis”. This was developed by our team in Bristol. In this method we identify important features of the strategies - “components” - that we can compare across many different studies. The method allows us to learn about what types of strategies work best, by telling us whether each component is important._x000D_ _x000D_ We will also look closely at the gender, ethnic backgrounds, and socio-economic backgrounds of the children involved in the studies to see if these aspects affect how well the different strategies work. Furthermore, we will look at how much the different strategies cost._x000D_ _x000D_ Two important stages of the project are the opening and closing stages. At the start, we will hold workshops with children and young people, parents, teachers and public health specialists to develop the “components” that we will use to analyse the studies. At the end of the project we will assemble these people again to look at the findings. Together we will make some recommendations on how we might prevent childhood obesity in future.

Lay abstract: BACKGROUND: _x000D_ Obesity is a risk factor for numerous chronic diseases, and is now established as a predictor of high severity COVID-19. It is costly to society, with the NHS spending in the region of £6 billion on ill-health relating to obesity each year, and is inequitably distributed in the population. Last year, 10% of children entering primary school in England were obese, and this prevalence more than doubled during school years._x000D_ _x000D_ Many interventions have been developed to try and prevent obesity in childhood. There is a vast literature on the topic, and there have been numerous systematic reviews and meta-analyses. A key systematic review is the Cochrane Review on interventions for preventing obesity in children. It includes 86 randomized controlled trials (RCTs) of 89,936 children aged 6 to 12, and 29 RCTs of 40,549 young people aged 13-18, and finds that physical activity interventions and combined diet and physical activity interventions have a small effect on average, but with notable variability of effects across studies. This variability, which must have some cause, makes us believe there is valuable information in the data that has not been adequately explored._x000D_ _x000D_ AIM: _x000D_ We will conduct a novel, sophisticated synthesis of the robust evidence in this area, offering the potential to unearth intervention features of both upstream and downstream interventions that are more likely to be effective in public health practice._x000D_ _x000D_ METHODS: _x000D_ We will start by updating the evidence in the Cochrane Review for the age group 5-18. We will supplement this with robust non-randomized evidence in order to include further community-level and population-level interventions. We estimate that we will add approximately 120 extra RCTs and 50 non-randomized studies to the evidence base. We will then develop a meaningful strategy for synthesizing the findings of the identified studies. Specifically, we will develop an analytic framework that incorporates all of the key attributes of interventions, participants, contexts and systems that are likely to explain differential effects of attempts to prevent obesity in children. We will do this by drawing on existing frameworks and by working closely with key groups including young people and those in the public health and educational sectors. We will use this analytic framework to code different features of the included studies, and make this coded dataset freely available._x000D_ _x000D_ The heart of the project will be a state-of-the-art evidence synthesis of the randomized and non-randomized evidence, motivated and informed directly by the analytic framework. The analysis will exploit component-based network meta-analysis methods, and will be implemented in a Bayesian framework._x000D_ _x000D_ We will request individual participant data from all of the included RCTs. We will use these primarily to investigate inequities, addressing how effects of interventions vary according to aspects such as socio-economic background, educational status, gender and ethnic background. In addition, we will collate all the available information about the costs of the interventions studied._x000D_ _x000D_ To conclude the project, we will hold an expert panel meeting to interpret and deliberate on the findings. Those involved in shaping the analytic strategy will be reconvened, and will work with us to produce recommendations for practice and for future research.

Research activity codes: 3.1 PRIMARY PREVENTION INTERVENTIONS TO MODIFY BEHAVIOURS OR PROMOTE WELL-BEING;3.2 INTERVENTIONS TO ALTER PHYSICAL AND BIOLOGICAL ENVIRONMENTAL RISKS
Health categories: CANCER AND NEOPLASMS;CARDIOVASCULAR;METABOLIC AND ENDOCRINE;ORAL AND GASTROINTESTINAL;STROKE