RESUMO
There is a difference between bringing parties together and making them work effectively. We present a case study of an intersectoral food policy Committee, part of a three-tiered coalition nested within local municipal government, which sought to promote and nutrition in a rapidly growing metropolitan region by tackling food supply issues in the first instance. This was new territory for all players. After 12 months, the group felt it was floundering and requested an evaluation. In-depth qualitative interviews with committee members (n = 21) and quantitative assessment of Committee processes revealed insufficient mechanisms for engaging new members, conflict between perceived roles for the group and a notable lack of confidence in the group's capacity to achieve its goals, or outcome efficacy. Feedback of the data and subsequent discussion led to a reform of project structure, stronger mechanisms to realize its goals and better incentive management, or ways to maximize the benefits and limit the costs for the diverse parties involved. The impact was reflected in a 4 year time series analysis of media releases, decision making and related municipal government actions. The study illustrates how theory-informed formative evaluation can help to improve health promotion practice.