The prevention of obesity, physical inactivity and obesogenic dietary intake among lower socioeconomic groups: a synthesis of evidence from Dutch interventions

The prevalence of obesity has substantially increased in the past decades, both in adults and in children. A large part of the population does not meet guidelines for physical activity and a healthy diet. Obesity prevention is one of the key challenges in public health in the Netherlands. Prevalence rates of obesity, physical inactivity and an unhealthy diet are highest in lower socioeconomic groups. Thus, there is an urgent need to target interventions to lower socioeconomic groups in order to improve population health and to reduce socioeconomic inequalities in health. However, still little is known about the effectiveness of interventions aimed at the prevention of obesity and the promotion of physical activity and a healthy diet in lower socioeconomic groups. Over the last years, many interventions aimed at preventing obesity and promoting physical activity and a healthy diet in the general population have been conducted in the Netherlands, including mass media campaigns, (computer)-tailored interventions, environmental interventions, school- and community-based interventions and interventions via the health care system. While these studies often measured indicators of socioeconomic position, effectiveness was hardly investigated for socioeconomic groups separately. Thus, there is a huge source of important information available that is currently not used. It is the main purpose of this project to investigate the differential effectiveness across high and low socioeconomic groups of Dutch interventions aimed at the prevention of obesity, the promotion of physical activity and a healthy diet among children, adolescents, adults and elderly. To achieve this aim, a broad range of existing Dutch interventions will be re-analysed for higher and lower socioeconomic group separately. In a feasibility study, principal investigators of 25 eligible studies were informed about the proposed project, were asked if their evaluation studies included indicators of socioeconomic position and if they were willing to participate in the project. The study showed that, except for 1 study where socio-economic position was measured at the neighbourhood level, all other studies had measured individual indicators of SEP, and that there is a great willingness by all principal investigators to participate in this project. A careful selection of studies will be made, assuring sufficient studies with different outcomes (anthropometrical outcomes, physical activity and diet), types of interventions and age groups. A general plan of analysis will be developed and used as a guide for the re-analysis of the studies. Results from all studies included in the project will be synthesised using a recently developed tool for this specific purpose (e.g. harvest plotting). Studies will be classified in one of three groups: a negative social gradient (intervention more effective in lower socioeconomic groups), no gradient, or a positive gradient. Harvest plots will be made for the different outcomes, age groups and for different types of interventions. From each intervention study, additional information will be collected about the aim of the intervention, the setting, the sources used in the intervention, the channel used, and the intensity and duration of the intervention. Comparison of this information across the three ‘gradient-groups’ will provide information why some interventions are more (or less) effective in lower socio-economic groups. This information will be transformed in recommendations for the development of interventions specifically suitable for lower socio-economic groups. This information will be made available for health promotion professionals and researchers.