Background: Policy is frequently identified in the behavioural nutrition and physical activity research literature as a necessary component of effective research and practice. The purpose of this commentary is to promote a dialogue to contribute towards the further development of conceptual understandings and theories of the relationship between policy practice and behavioural research and how these twoactivities might work synergistically to improve public health outcomes.Methods: Drawing on policy and public health literature, this commentary presents a conceptual model of the interaction and mediation between nutrition and physical activity-relevant policy and behavioural nutrition and physical activity research, environments, behaviours and public health implications. The selling of food in school canteens in several Australian states is discussed to illustrate components ofthe relationship and the interactions among its components.Results: The model depicts a relationship that is interdependent and cyclic. Policy contributes to the relationship through its role in shaping environmental and personalcognitive determinants of behaviours and through these determinants it can induce behaviour change. Behavioural research describes behaviours, identifies determinants of behaviour change and therefore helps inform policy development and monitor and evaluate its impact.Conclusions: The model has implications for guiding behavioural research and policy practice priorities to promote public health outcomes. In particular, we propose that policy practice and behavioural research activities can be strengthened by applying to each other the theories from the scientific disciplines informing these respective activities. Behavioural science theories can be applied to help understand policymaking and assist with disseminating research into policy and practice. In turn, policyscience theories can be applied to support the institutionalisation of commitments to ongoing behavioural research.