Health, urban planning, societal, and demographic developments over the last 150 years have led to the expansion of cities through urban sprawl. This has a considerable impact on natural resources, the environment, and planetary health. One strategy which can be adopted to counter these negative effects is urban densification, the methods and mechanisms of which are discussed in other articles in this issue. This text focuses on its direct and indirect impacts on health. In particular, it describes the various mechanisms that govern the processes of salu- togenesis (factors and mechanisms that support health) and pathogenesis that are constantly at work in urban environments. Healthy urban planning is proposed here as an effective pre- ventive strategy to reinforce salutogenesis and reduce pathogenesis which can be adopted by local decision-makers and more widely promoted among professionals and the population.