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Policies aiming to prevent childhood obesity are informed by research that mostly explores ways of changing the behaviour of individuals. An in-depth analysis of 153 research papers found that most interventions aim to teach children to improve their diet and/or take part in more physical activity. 

This has been the mainstay of interventions studied for almost 30 years, while rates of childhood obesity have increased. It is now accepted that a collection of interventions is required to change the environments that children grow up in; a shift in focus is needed. This systems approach involves multiple organisations and sectors working together to change factors that lie outside of an individual’s control. These factors include the environments we live and work in, our social circles, media and marketing messages, and government policies. But research into this broader approach is lacking. 

The current study found that most existing high-quality randomised controlled trials (RCTs) target individual behaviours; which the authors suggest may be influencing policy. They say that researchers, research funders and policymakers need to study interventions and policies that change the wider environment that children grow up in.

What’s the issue?

Obesity is a complex public health issue caused by more than 100 interconnected factors. Although personal lifestyle choices about diet and physical activity play a role, it is now accepted that the most important drivers of obesity lie beyond the individual’s control. They include the environments we live in, media and marketing influences, government policies, and the state of the economy. 

Local authorities acknowledge that the causes of obesity are complex, yet previous work by the same researchers showed that two-thirds of local authority policy targets individuals’ behaviour. Knowledge of the problem is not translating into how it is addressed. 

Public health professionals and policy makers regularly draw upon the findings from rigorous research. Randomised controlled trials (RCTs), often seen as the gold-standard of research evidence, are usually designed to look at the effects of specific interventions. The authors suspected that most RCTs in obesity prevention will target behaviour change in individuals. High-quality Cochrane Reviews gather the findings of RCTs on a specific subject and can inform health policy. So in obesity, these influential Reviews could be focusing mainly on individuals. This in turn could drive policy-making to target individuals rather than their environments.

To test this hypothesis, the authors analysed the most recent Cochrane Review on “Interventions for Preventing Obesity in Children”. It has been updated four times since it was first published 20 years ago. The authors wanted to explore whether the evidence in the Review reflects our understanding of the need for a systems approach. 

What’s new?

The influences on our health – or determinants – include social, economic and environmental factors. The determinants of health are often considered in five broad groups: biological, individual lifestyles, social and community, living and working conditions, wider conditions. Previously, the researchers had classified hundreds of causes of obesity into these groups

In this study, they looked at the 153 RCTs in the 2019 Cochrane Review and, for each, considered which determinants were being targeted. This allowed them to make a comparison between the causes of obesity and the studies seeking to prevent it.  

The study found that: 

    • individual lifestyle factors (such as diet, physical activity) account for one in six (16%) causes, but more than half (58%) interventions 
    • living and working conditions (education, housing, transport) account for one in three (33%) causes and slightly more (37%) interventions
    • wider conditions (economic climate, culture, income equality) account for one in four (27%) causes and hardly any interventions (1%)
    • social and community factors (family, friends, neighbours) account for one in seven (14%) causes and one in 27 (4%) interventions 
    • biological factors (such as age, genetics) account for one in ten (10%) causes of obesity with no interventions targeted at them.

Some studies into ‘living and working conditions’ actually targeted individuals; they involved training teachers to educate children on healthy behaviours. This means that, overall, the vast majority (92%) of RCTs had a focus on individual lifestyles. Yet around 60% of the causes of obesity lie outside of the individual’s control.  The focus of interventions has remained unchanged since the Cochrane Review was first published in 1993.  

Why is this important?

These findings suggest that there is a long-standing imbalance between the known causes of obesity and the focus of RCTs to prevent childhood obesity. Public health officials often base policy on the best evidence available. But this study finds that the evidence base itself is biased towards interventions that try to encourage individuals to change their behaviour.

Other research already suggests that attempting to reduce childhood obesity by focusing on lifestyle factors alone is unlikely to be effective. The findings of this paper warn that we are not addressing childhood obesity in the most effective way. The current approach is unlikely to drive change.

What’s next?

The paper highlights the need for a major shift in how we address childhood obesity, and the types of evidence that are used to inform policy. Approaches have remained unchanged for almost three decades while rates of obesity have risen.

Policymakers should be aware that the studies they look at could be biased towards tackling diet and physical activity at an individual level. Interventions and policies that address the wider causes of childhood obesity are needed. Attempting to address issues like living and working conditions may be more successful than trying to persuade individuals to change their lifestyle. 

Research funders could help shift the focus by funding alternative types of research. RCTs are designed to look at the effect of individual interventions; other types of research may be better suited to looking at multiple factors and the wider context in which children grow up.

Researchers themselves could explore new approaches to research, with the aim of changing the wider conditions that encourage obesity. Other research designs, such as natural experiments (for example, seeing what happens when a soft drinks levy is introduced), may be better suited to studying the prevention of obesity. Researchers, funders, and policymakers could work more closely to ensure that new policies are fully evaluated to see if they work. 

The researchers have shared a short overview of their findings with a wide range of Public Health teams, Members of Parliament, and professional bodies. They aim to encourage a change in policy.

You may be interested to read

The full paper: Nobles J, and others. A secondary analysis of the childhood obesity prevention Cochrane Review through a wider determinants of health lens: implications for research funders, researchers, policymakers and practitionersInt J Behav Nutr Phys Act 2021;18:22. 

Public Health England’s guidance on whole systems approach to obesity

A recent paper from the same lead researcher: Nobles J, and others. Understanding how local authorities in England address obesity: A wider determinants of health perspective. Health Policy 2019;123:10. 

An analysis of health inequalities in England: Marteau TM, and others. Changing behaviour: an essential component of tackling health inequalities. BMJ 2021;372:332. 

A review of policy approaches to tackling obesity: Theis DR, and White M. Is Obesity Policy in England Fit for Purpose? Analysis of Government Strategies and Policies, 1992–2020. The Milbank Quarterly 2021. 

Website for the Obesity Health Alliance, a coalition of organisations aiming to reduce obesity.

Research exploring obesity prevention interventions in schools: Ijaz S, and others. Preventing Childhood Obesity in Primary Schools: A Realist Review from UK Perspective. International Journal of Environmental Research and Public Health 2021;18:13395


Funding: This research was supported by NIHR ARC West, which also paid the Article Processing Charge; and by NIHR Applied Research Collaboration (ARC) North East and North Cumbria.

Conflicts of Interest: Three of the researchers were involved in the Cochrane Review on Interventions for Preventing Obesity in Children, which was studied. The lead researcher was involved in the development of the Public Health England Action Mapping Tool which was used in this study, as well as the broader Whole Systems Obesity programme. 

Disclaimer: NIHR Alerts are not a substitute for professional medical advice. They provide information about research which is funded or supported by the NIHR. Please note that views expressed in NIHR Alerts are those of the author(s) and reviewer(s) and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care.

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Study author

Fundamentally, we need to start looking at policies and interventions that affect entire populations and require less individual agency. A good example of this is the Soft Drinks Industry Levy, otherwise known as the “sugar tax”. This has the potential to change the dietary patterns of the population as a whole, with little to no effort required by the individual. This type of policy might be more challenging to evaluate, but it offers the potential to reduce rather than widen inequality.

We need to try and understand more about how research informs policy in this field. Scientists need to improve the dissemination and implementation of their findings, and to understand more about the policy context so that their research can feed directly into policy agendas in a timely fashion. 

I would also like to keep pushing the need for different research designs in Public Health. We cannot be reliant on randomised controlled trials. We need alternative approaches to evaluate the complexity of what goes on in public health policy-making.

James Nobles, Senior Research Associate, Bristol Medical School, University of Bristol 

Obesity Health Alliance

It’s apparent from rising levels of obesity in children and the widening gap between the most and least deprived children that approaches to addressing childhood obesity in the last 20 years have been largely ineffective.

The causes of childhood obesity are complex, but it’s too often reduced to a narrative of bad parenting and bad choices with more education presented as the solution. This can make it more challenging for charities and public health groups to advocate for the structural policies, such as the soft drinks industry levy and restrictions on food marketing, which are more likely to positively shift children’s dietary behaviour in the longer-term. This study provides solid evidence to help the Obesity Health Alliance members make this case to policy-makers.” 

Caroline Cerny, Alliance Lead, Obesity Health Alliance 

Young person 

I’m lucky because there’s nothing to stop me doing lots of exercise and eating quite healthily. I row because I love it, it’s sociable and a great environment. But you have to be quite motivated to join a club and start going. My parents think sport is a good thing, they drive me places and come to my races. But not everyone has that. A lot of the people in my class don’t do much exercise, especially if they didn’t start when they were slightly younger. It would be better if there were more opportunities at school. There isn’t much sport at all, and it would be really helpful if there was casual sport, where you don’t have to be committed and you can just do it for fun. 

I eat reasonably well, and usually take a packed lunch because the food at the school canteen is not particularly good for you. The main meals are probably OK but at break, the snacks are things like pizza, tray bakes, and biscuits. There’s sometimes grapes so technically you can eat healthily, but the odds are stacked against you.” 

Clara Sayers, Age 15, Oxford  


This study will contribute to the growing recognition that interventions and research on mid and upstream causes (such as living and working conditions, and wider factors) will likely be important in addressing the childhood obesity problem. It may encourage policymakers and research funders to evaluate the predominant focus on downstream interventions. 

The paper could also stimulate discussion on the early years, which is key to prevention. A stronger research focus is needed on the under 5s; only one in four of the RCTs focused on this age group.  The paper also advocates interventions that target children from disadvantaged areas as inequalities may be widened when individual lifestyle factors are targeted.

A further area to consider is the reliance on RCTs to inform policy, given that it is much more difficult to evaluate living and working conditions, and wider factors, using RCTs. Research funding structures are often organised in a way that favour RCTs, but there may be a benefit in expanding further work to consider other research methods.

Simon Russell, Research Manager, Obesity Policy Research Unit, Great Ormond Street Institute of Child Health, London  

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