10 February 2021
An analysis of the studies included in the Cochrane review ‘Interventions for Preventing Obesity in Children’ has revealed a strong bias towards interventions that aim to change individual “lifestyle” behaviours. It is important to understand the evidence underpinning the review as it is widely used by policymakers internationally. This bias could influence the types of policy that governments put in place to prevent childhood obesity.
The team, including researchers from NIHR ARCs West and North East and North Cumbria (NENC) analysed the 153 randomised control trials – the best test of an intervention – that are included in the Cochrane review. They used a tool from Public Health England to categorise the types of interventions tested in each trial into:
They also looked at how the focus of the trials has changed between 1993 (the earliest trial) and 2015 (the most recent trials), and whether there was any difference in the focus of interventions for various age groups (0-5 years, 6-12 years, 13-18 years).
Over the last 30 years, research has shown that healthier environments are needed to prevent childhood obesity. Obesity is the result of many different factors that all connect to one another. These include how our environment enables physical activity, the influence of social circles, genetic factors and whether people already have a tendency to gain weight. In 2007, a government report identified 108 factors that contribute to the population’s levels of obesity.
Many of these factors are beyond an individual’s control, for example those that are linked to socioeconomic status or the systems that people live in (referred to as “upstream” factors). Factors that relate to individual lifestyle, such as healthy eating or doing more sport, are called “downstream” factors. There is plenty of evidence to suggest that upstream factors such as where people live or the type of work they do have a direct influence on downstream factors, and in turn, their health.
Despite broad acknowledgement that obesity is caused by a wide range of factors, over 90 per cent of the trials had some focus on changing individual lifestyle factors. This was most often achieved through the delivery of educational sessions. There was also a strong emphasis on living and working conditions, although this mostly meant upskilling teachers so that they could teach children about how to improve “lifestyle behaviours”.
The researchers also found that the focus of these studies hadn’t changed much since 1993. They persisted in their focus on directly changing diet and physical activity, despite demonstrating very limited effectiveness. The focus of interventions was also consistent between those targeting children from different age groups.
Dr James Nobles, Senior Research Associate at NIHR ARC West, said:
“Our findings suggest that there is an imbalance between the causes of obesity and what the trials to prevent childhood obesity focus on. This skewed focus has endured since the early 1990s and persists despite the growing recognition that population-level obesity is a complex systems issue.
“Our previous research has found that the most interventions carried out by local government tends to focus on downstream factors, despite this growing evidence that these kinds of interventions have limited impact on population levels of obesity. Our new research has shown that this bias is also present in the evidence that policymakers use to inform their decision-making.
“We hope that our findings add to the conversation on what’s evaluated in childhood obesity prevention studies, and how it’s evaluated.”
Professor Carolyn Summerbell from Durham University co-authored the report. Professor Summerbell is Deputy Director of Fuse, the Centre for Translational Research in Public Health, and a member of the NIHR ARC North East and North Cumbria. She said:
“Childhood obesity is a major public health challenge, and we know from research over the last 30 years that childhood obesity results from multiple, complex factors – the majority of which are outside an individual’s control, including living environment and socio-economic factors. Despite this, our analysis has shown that the majority of interventions aimed at supporting children to achieve a healthy weight have focussed on individual lifestyle factors – including diet and exercise.
“We hope the findings of our study will challenge funders, researchers, policymakers and practitioners to reflect and re-think when designing interventions, and begin to shift the focus to the environments that children are growing up in, rather than their individual actions.”
A secondary analysis of the childhood obesity prevention Cochrane Review through a wider determinants of health lens: implications for research funders, researchers, policymakers and practitioners
James Nobles, Carolyn Summerbell, Tamara Brown, Russell Jago, Theresa Moore
Published in the International Journal of Behavioural Nutrition and Physical Activity