Rationale Most food in the UK comes from commercial food companies, which contribute to the environments that drive what we eat. Many food companies need to change to support healthier diets. Population health researchers need to understand how food companies shape food choices and identify levers for change. This may require that researchers interact with industry. However, there is no explicit consensus among researchers regarding what constitutes acceptable or effective interaction. This has led to confusion over potential conflicts of interest, which could obscure findings and undermine scientific integrity. We aimed to build international consensus on what constitutes appropriate interactions between population health researchers and the food industry.

Methods We undertook a systematic scoping review of published and grey literature, and a two-stage international Delphi study of population health researchers. Scopus and Pubmed were searched to May 2017 for articles in English referring to principles guiding interactions between population health researchers and the food industry. We also asked experts to nominate documents, conducted an advanced Google search and hand searched reference lists. We thematically analysed included articles to saturation to derive principles. A two-round, online Delphi survey was undertaken to determine and build consensus on these principles, using a multi-pronged, purposeful approach to recruitment of researchers internationally. Consensus was defined as 80% agreement on each statement. Content analysis of qualitative feedback informed the second Delphi round. Findings provided the starting point for a two-day international workshop, in which we discussed a framework and principles for guidance.

Findings Our systematic review identified 56 principles in five key areas: governance of funding, risk assessment, maintaining standards of governance, ensuring transparency and improving publication standards. 100 researchers completed the first round of the Delphi and 92 the second. After round two, there was consensus on 39 statements (68%). Detailed comments by participants helped to modify principles. The international workshop identified the need for guidance as a ‘thinking tool’ rather than set of rules, offering support for researchers to assess risks and manage potential conflicts of interest throughout the research process. Effective guidance will need the support of researchers, funders and journals.

Discussion This research has built consensus on the need for guidance, and identified an optimal approach for assessing risk, prevention and management of conflicts of interest in interactions between population health researchers and the food industry. Further work is needed to finalise, pilot test and seek endorsement for evidence informed guidance.