This study explored approaches to promoting active lifestyles (PAL) in schools which aimed to inform and develop physical education (PE) trainees and teachers’ health-related philosophies and pedagogies. Thirty-two secondary school PE trainees and teachers involved in a University-based Initial Teacher Education partnership in England participated in this study during the period 2015–2019. The participants were involved in professional development which included an introduction to research-informed PAL ‘paradoxes’ associated with promoting active lifestyles. Participants were asked to review their own health-related philosophies and practices in light of these paradoxes and were encouraged to use them to influence their own pedagogies as well as those of colleagues/peers. Participants found the PAL paradoxes interesting, surprising and perplexing; expressed a keen desire to address and solve them; and experienced the joys and challenges of influencing colleagues’/peers’ health-related philosophies and pedagogies. The findings suggest that this innovative low-cost, flexible and accessible approach to pedagogical change has the potential to engage PE teachers, increase their effectiveness as promoters of physical activity, and to greatly enhance the subject’s contribution to public health. This is significant, given calls for new pedagogical approaches and teachers’ previously reported lack of engagement in professional development in this area.