Background

Both internationally and in the UK, there is widespread concern about increasing rates of obesity and overweight. There is interest from both policy-makers and researchers in the social and environmental determinants of obesity, including factors related to the physical environment, social values, technology and the economy. Children and young people are an important focus of initiatives to prevent or reduce obesity. However, these policy concerns are not yet matched by a robust evidence base on the effectiveness of social and environmental interventions.

Aims and review question

This report describes a systematic map of existing research reviews relating to social and environmental interventions aimed at reducing or preventing obesity and overweight. Its focus is on research which has included children and young people.

Our research questions were:

• What are the methodological characteristics and scope of reviews which have been conducted on ‘social and environmental’ interventions for reducing or preventing obesity and obesity-relevant behaviours?
• What types of interventions are evaluated and which outcomes do the reviews measure?
• What is the focus of each review and how reliable are the findings?
• How do researchers conceptualise ‘social and environmental’ interventions?
• What does this work suggest in the way of future research priorities?

Methods

We located reviews through searches of databases in several fields, as well as specialist websites and contact with experts. Database searches used a broad strategy to maximise inclusiveness. Reviews were included if they: investigated some obesity-relevant topic; reviewed the effectiveness of interventions; included the 4-18 age group; were published in 1996 or later; and focused on social and environmental interventions. Included reviews were coded and quality-assessed by two reviewers independently. We did not look in detail at the studies included in the reviews because of the wide variation in the way that authors presented their study findings.

Results

We found 54 reviews. Thirty-two of these were classified as systematic reviews (reporting their aims, search strategy and inclusion criteria). The reviews covered a wide range of intervention types and settings. Most of the reviews covered the population as a whole and did not have a specific focus on children or young people. We divided the reviews into seven groups defined by topic. 

Mass media (N=8; systematic reviews N=5)

These reviews evaluated mass-media campaigns (TV, radio, internet), either alone or in combination with individual-level interventions. Most reviews (N=5) focused on physical activity.
Financial incentives and pricing strategies (N=3; systematic reviews N=2)
These reviews included a range of strategies which changed the relative price of food items to increase healthy eating. These strategies included ‘micro-environmental’ interventions which were set in individual retail sites as well as provision of extra resources to individuals, and ‘macro-environmental’ interventions which took place on a wider scale, such as taxes and subsidies. All these reviews focused on healthy eating.
Point-of-sale information and availability (N=3; systematic reviews N=2)
These reviews focused on interventions to promote healthy eating through changing the availability of food in local settings, and/or altering its attractiveness through point-of-sale information and marketing, in either public eating places or the home. All these reviews focused on healthy eating. 

Active transport (N=3; systematic reviews N=3)

Three reviews focused on the promotion of active transport (walking and cycling). These reviews all included a wide range of intervention types, from individual-level behaviour change programmes to mass media, community events, and changes to the physical environment. 

School-based environmental change (N=6; systematic reviews N=4)

These reviews evaluated a range of multi-component interventions taking place in the school setting. The social and environmental components of the interventions included modifications to the physical environment, school rules and policies, and various strategies to impact on the social environment within the school. Some programmes also included educational curricula and/or physical exercise classes. The reviews focused equally on healthy eating and physical activity.

Community-based programmes (N=16; systematic reviews N=8)

These reviews evaluated multi-component projects in a community setting. The programmes included in these reviews generally focused on a geographical area and used multiple settings (e.g. workplaces, public community sites, schools, food retailers, mass media). Social and environmental components included physical environmental change, policies and regulations, community mobilisation and development, and mass media and point-of-sale campaigns; many interventions also included individual-level components such as education and screening. Five reviews focused on reducing the risk of cardiovascular disease, and one on diabetes; the remainder looked at healthy eating, physical activity, or obesity-related behaviours in general.
Reviews containing programmes in more than one category (N=15; systematic reviews N=8)
These reviews included several different intervention settings and types. Some focused on social and environmental interventions, whilst others also included individual-level strategies. The reviews were split between those that focused jointly on healthy eating and physical activity and those that focused only on physical activity. 

Conclusion

Building a strong evidence base for policy means locating and using the most relevant and reliable research. This research includes both individual primary studies and reviews of research areas and topics. The ‘map of reviews’ described in this report shows that there is a substantial body of review-level evidence. However, the reviews varied widely in quality. Although 32 of the 54 reviews that we found used a systematic approach, 22 (41%) did not.
Authors used a wide range of terms and concepts to identify the ‘social and environmental’ field. Some reviews defined it as all ‘population-based’ interventions, that is, all which are not primarily targeted at the individual level or at particular high-risk groups. Some reviews specifically sought interventions which combined individual-level and social or environmental components. A useful distinction made by several reviews was that between ‘midstream’ and ‘upstream’, or ‘local’ and ‘structural’ interventions: i.e. between interventions limited to a particular setting such as a school, and those which address broader determinants of behaviour such as policy or the physical environment in the community.

Research and policy implications

Research priorities identified by review authors included improving the design of effectiveness evaluations and, particularly, using study designs which include a control group for evaluating policy; including cost-effectiveness analysis and improving measures for other outcomes; measuring impact for population subgroups; investigating impact on health inequalities; conducting and integrating qualitative research; and developing a common framework.

Our overview of the 54 reviews identified some obvious gaps. Relatively little review-level evidence is available on the impact of social and environmental interventions for children and young people, particularly younger children (under age 11). Most reviews considered research relating to whole populations. Reviews contained limited evidence from robust prospective study designs relating to large-scale macro-level interventions such as policy change, taxation, or changes to the built environment. There were few systematic reviews of community-based programmes which primarily targeted obesity and measured a range of outcomes. There were very limited data relevant to health inequalities or to the cost-effectiveness of interventions. It was not always clear how review authors conceptualised ‘social and environmental’ or how the concept was operationalised in the review. Future research priorities include:

• Reviews focusing on the impact of interventions on children and young people,
• Reviews focusing on ‘structural’ or ‘macro’ interventions, such as policy interventions or changes to the built environment;
• Reviews integrating data from intervention studies and the findings of qualitative research and correlational studies;
• New systematic reviews of community-based programmes for obesity, healthy eating, and physical activity, especially for a UK population.
• Reviews examining the effectiveness of interventions in reducing health inequalities and improving the health of disadvantaged groups
• A clearly defined theoretical framework for obesity-relevant research, developed through consensus; and
• Policies for addressing the problem of childhood obesity should take account of the considerable review-level evidence about the effectiveness of different social and environmental approaches.