Purpose Physical distancing policies in the state of New South Wales (Australia) were implemented on March 23, 2020, because of the COVID-19 pandemic. This study investigated changes in physical activity, dietary behaviors, and well-being during the early period of this policy. Methods A cohort of young people aged 13–19 years from Sydney (N = 582) were prospectively followed for 22 weeks (November 18, 2019, to April 19, 2020). Daily, weekly, and monthly trajectories of diet, physical activity, sedentary behavior, well-being, and psychological distress were collected via smartphone, using a series of ecological momentary assessments and smartphone sensors. Differences in health and well-being outcomes were compared pre- and post-implementation of physical distancing guidelines. Results After the implementation of physical distancing measures in NSW, there were significant decreases in physical activity (odds ratio [OR] = .53, 95% confidence interval [CI] = .34–.83), increases in social media and Internet use (OR = 1.86, 95% CI = 1.15–3.00), and increased screen time based on participants' smartphone screen state. Physical distancing measures were also associated with being alone in the previous hour (OR = 2.09, 95% CI: 1.33–3.28), decreases in happiness (OR = .38, 95% CI = .18–.82), and fast food consumption (OR = .46, 95% CI = .29–.73). Conclusions Physical distancing and social restrictions had a contemporaneous impact on health and well-being outcomes associated with chronic disease among young people. As the pandemic evolves, it will be important to consider how to mitigate against any longer term health impacts of physical distancing restrictions.

BackgroundEvidence-based decision-making is an important foundation for health policy and service planning decisions, yet there remain challenges in ensuring that the many forms of available evidence are considered when decisions are being made. Mobilising knowledge for policy and practice is an emergent process, and one that is highly relational, often messy and profoundly context dependent. Systems approaches, such as dynamic simulation modelling can be used to examine both complex health issues and the context in which they are embedded, and to develop decision support tools.ObjectiveThis paper reports on the novel use of participatory simulation modelling as a knowledge mobilisation tool in Australian real-world policy settings. We describe how this approach combined systems science methodology and some of the core elements of knowledge mobilisation best practice. We describe the strategies adopted in three case studies to address both technical and socio-political issues, and compile the experiential lessons derived. Finally, we consider the implications of these knowledge mobilisation case studies and provide evidence for the feasibility of this approach in policy development settings.ConclusionParticipatory dynamic simulation modelling builds on contemporary knowledge mobilisation approaches for health stakeholders to collaborate and explore policy and health service scenarios for priority public health topics. The participatory methods place the decision-maker at the centre of the process and embed deliberative methods and co-production of knowledge. The simulation models function as health policy and programme dynamic decision support tools that integrate diverse forms of evidence, including research evidence, expert knowledge and localised contextual information. Further research is underway to determine the impact of these methods on health service decision-making.