Abstract
Unhealthy commodity industries (UCIs) such as tobacco, alcohol, gambling, ultra-processed food and beverage producers are known to influence policy-making to advance their interests, often to the detriment of public health goals. This study mapped the complex system underpinning UCI's influence on public health policy formulation in the UK and identified potential interventions to shift the system towards being able to better attain public health goals. We conducted a participatory systems mapping workshop with ten experts to build a causal loop diagram (CLD) and identify potential interventions to address UCI's influence on public health policy development. The resulting CLD depicts a highly interconnected and reinforcing system driving UCI's involvement in public health policy formulation across five thematic areas. Among the most connected elements were the 'dominance of market mechanisms', 'perception of partnership as good governance principle', 'industry involvement lending perceived legitimacy to the policy formulation process', 'industry is seen as part of the solution' and 'industry ties to policy-makers'. Participants identified a total of 22 interventions within this system. Analysis of the CLD and interventions identified the potential for two key paradigmatic changes in this complex system: de-normalizing the perception of unhealthy commodity industry actors as legitimate stakeholders in policy formulation; and prioritizing public health and wellbeing objectives over profit and economic gain. In order to shift the system towards better attaining public health goals, interventions should reinforce each other and be supportive of these two key paradigmatic shifts.