Group model building to address dietary health inequalities in English local authorities: a randomised controlled trial with process evaluation

In the UK, people living in less affluent circumstances consume less healthy diets. This means they also suffer from more diet-related disease. For example, adults living in households with the highest income are twice as likely to meet the 5-a-day fruit and vegetable target compared to those living in households with the lowest income. In June 2024, 14% of UK households experienced food insecurity in the last month. These dietary health inequalities (DHI) are partly due to healthier food being more expensive and less available locally. Other complex processes at national and international levels influence DHI. For example, the war in Ukraine had a significant impact on food costs worldwide and some countries mitigated this better than others. Food companies often resist regulation to support healthier diets because they worry it might reduce their profits. Less is known about local influences on DHI. THE CHALLENGE THIS PROJECT ADDRESSES These wider influences on DHI mean simply encouraging people to make healthier 'choices' is not enough. Wider approaches that change the social, physical and financial context in which choices are made are required. These need cross-sector collaboration. Systems thinking is one way to approach problems like DHI with many causes. Group model building (GMB) is a structured approach that uses systems thinking to achieve a shared understanding of a problem and identify potential solutions. GMB can support cross-sector collaboration. It is not yet known if GMB changes what solutions are ultimately delivered. We recently co-developed a dietary-focused GMB intervention with public health teams. We will refine and test this in a randomised controlled trial (RCT) and process evaluation in English Local Authorities (LAs). RCTs are experiments which provide some of the most robust evidence on the effectiveness of interventions. Through structured observations of GMB we will explore local influences on how people think about DHI and so provide further information on local influences on DHI. RESEARCH QUESTIONS Our research questions are: What is the impact of the intervention on the number of policies with the potential to impact on, and achieve systems change in, DHI in more deprived English LAs? What is the impact of the intervention on participants' perceptions of: understandings of DHI commitment to addressing DHI confidence in addressing DHI strength of local collaborations to address DHI? How do local stakeholders understand DHI and their potential solutions, how does this evolve during the course of the intervention? What are the costs of the intervention? POTENTIAL APPLICATIONS AND BENEFITS Key outputs from our work will be greater understanding of: the potential of a GMB intervention to reduce DHI (call Theme 2) local influences on understanding of, and potential solutions to, DHI (call Theme 1) If we find the intervention to be effective then citizens in LAs receiving the intervention are likely to benefit. External facilitators delivering the intervention to more LAs using our materials could lead to even greater benefit. LAs may also benefit from repeating the intervention in the future. Our key audiences will be those working on food in local, regional and national government, as well as other researchers. We will share findings through written and video summaries and disseminate these via direct mailing, social media, targetted conversations, presentations at relevant conferences and networks, journal articles and a dissemination workshop.