Promoting physical activity represents a major public health opportunity due to its significant impact on physical and mental health. Despite ongoing efforts, public health interventions often struggle to achieve sustainable behavioral changes. Instead of explicitly or implicitly attributing such failures to a lack of individual motivation, it is essential to consider the characteristics of contemporary environments that promote physical inactivity. We propose an explanatory framework that integrates the theory of effort minimization in physical activity with the postulates of the ecological model of physical activity behavior. According to theory of effort minimization in physical activity, humans have an innate tendency to avoid physical effort, making it difficult to adopt an active lifestyle in environments where opportunities to minimize effort are pervasive. Complementarily, the ecological model emphasizes the key role of built environment in providing behavior settings-those social and physical situations that can promote and sometimes demand certain actions and discourage or prohibit others. Building from the theory of effort minimization in physical activity, we suggest that redesigning the built environment so that being active is the default behavioral option, while ensuring that it elicits positive affective responses, could be a decisive strategy. Such an approach could not only increase physical activity levels across the population but also help to reduce gender differentials and sociospatial inequalities in participation.