Accounting for the Climate Cost of Physical Activity Promotion: The PA-CARBON Framework and Three Case Studies

Background Physical activity promotion is central to chronic disease prevention, mental health, healthy aging, mobility, and social participation. It is also increasingly framed as a climate-relevant public-health strategy because active transport, activity-supportive urban design, local recreation, and community programs can reduce fossil-fuel dependence and strengthen resilience. Yet physical activity strategies can also generate greenhouse gas emissions from travel, facilities, construction, equipment, food, digital systems, events, and rebound consumption. This creates a need for a systematic approach that can assess both the health-promoting value of physical activity strategies and the emissions associated with their delivery. Methods Evidence on physical activity, climate change, active transport, sport, the built environment, community programs, greenhouse-gas accounting, life-cycle assessment, and public-health evaluation was reviewed. Framework development followed a theory-informed, best-fit, and adaptation process used in health-framework work: relevant parent frameworks were identified, their constructs were mapped to physical activity promotion and carbon-accounting requirements, gaps were specified, and the resulting framework was operationalized into reporting steps, data-quality tiers, functional units, and case-study tests. Evidence was selected based on relevance to intervention domains, accounting method, empirical emissions data, and case-study context, rather than on author identity. Case studies were selected purposively as maximum-contrast methodological tests: a transparent active-commute mechanism, a real active-travel infrastructure natural experiment in England, and a real community/primary-care program in Brazil. Results PA-CARBON is a six-step framework: classify the strategy; define the counterfactual; inventory gross emissions; estimate induced and avoided emissions; report outcome-linked metrics; and stress-test uncertainty and equity. A hypothetical active-commute program was climate-beneficial in most scenarios when car-km were displaced. London Mini-Hollands showed rapid infrastructure carbon payback if reduced car ownership translated into reduced vehicle-km, but results were sensitive to food and travel assumptions. Brazil's Academia da Saúde had a screening gross footprint of 4.75–8.49 tCO2e per polo-year, depending on food compensation, equivalent to 0.48–0.85 kgCO2e per participant-visit. Conclusions The climate cost of physical activity promotion is not inherent to movement. It is determined by the delivery system, counterfactual, induced behaviors, and avoided emissions. PA-CARBON provides a standards-compatible reporting layer that links greenhouse-gas accounting to active minutes, MET-hours, visits, car-km avoided, carbon payback, equity, and climate adaptation. Routine carbon reporting can help the field design strategies that simultaneously maximize health, equity, and climate benefits.