Associations Between the Built Environment and Adult Obesity and the Mediating Role of Physical Activity: A Systematic Review.

Associations between the built environment (BE) and adult obesity are well established. Physical activity (PA) is shown to mediate this association; however, no review has comprehensively synthesized the evidence required to understand this mediating relationship and its variation across different measures of the BE, PA, and obesity. Four electronic databases were searched, and 19 articles published between 2005 and 2022 were reviewed. PA partially explained the associations between the BE and obesity, with effects varying widely across studies (0.48%-48.7%). Objectively measured moderate-to-vigorous PA consistently mediated the association between walkability and obesity, with higher PA accounting for 8.5%-11.6% of the relationship. Domain-specific PA such as walking for transport mediated walkability-obesity associations, but only few studies examined such relationships. PA was an inconsistent mediator of associations between other BE exposures (street connectivity, land-use mix, accessibility, and greenspace) and obesity. PA's mediating role in the BE-obesity relationship is context-dependent; BE features that promoted PA in less dense urban areas of some countries showed different effects in denser urban settings of other countries. Despite limited longitudinal studies from diverse settings, evidence from this review suggests that the BE has the potential to facilitate PA and reduce global obesity and related chronic conditions.