Aims: This study aims to identify physical inactivity-related challenges and motives, based on reviews and supplemented by expert interviews with Danish national experts on physical inactivity, providing a general discussion of the subject ultimately generating knowledge useable in a Scandinavian context. Methods: This study is framed as a narrative review of scientific review literature on physical inactivity, limited to the general population. The review is supplemented by expert interviews with Danish national experts on physical inactivity. We used thematic coding of the included reviews, while using hermeneutic interpretation analysis for the expert interviews. Results: Based on 11 included reviews, we highlighted four themes based on our analysis of reviews: (a) socioeconomic determinants of physical activity; (b) life-course perspective; (c) physical inactivity and older adults aged 60+ years; and (d) intervention recommendations. The supplementary expert interviews revealed three additional themes: (a) the individual history with physical activity; (b) sporting organisation importance; and (c) society responsibility for physical inactivity. Conclusions: Collectively this study concludes, based on review and expert interviews, that a number of determinants and correlations for physical inactivity affect the individual from various socioecological levels. Based on this review, we suggest moving beyond the ‘upstream’ public health approach of randomised controlled trials and consider complex interventions targeting physical inactivity from several levels. Physical inactivity should be acknowledged as a ‘wicked problem’ that requires a systems-based approach instead of a single quick fix. Future work with physical inactivity would profit from focus on the life-course perspective, sporting clubs’ responsiveness and physical literacy.