Physical inactivity is now a significant driver of health and social inequalities among socioeconomically
disadvantaged communities and poses a major challenge to policymakers, worldwide. Although a vast amount of research has
focused on designing and evaluating interventions to increase physical activity, there remains little consensus on which
interventions are likely to work. In this narrative review, we build on previous reviews by not only examining what interventions
tend to work but by trying to understand why certain interventions tend to work, while others do not, through the lens of
behavioural science. We present a behavioural framework through which the existing body of physical activity research could be
viewed, in order to identify potentially effective mechanisms that would be likely to work in their intended domain. Our analysis
finds that while there is evidence that the physical and educational environment matter for increasing levels of physical activity,
interventions are more likely to be successful where they involve a social component. We conclude that a behaviourally
informed physical activity intervention would thus employ a set of focused educational and socially-mediated behavioural
mechanisms, within an appropriate physical environment
