Objective Low physical activity (PA) levels are associated with increased mortality. Improved measurement has resulted in stronger proven associations between PA and mortality, but this has not yet translated to improved estimates of the disease burden attributable to low PA. This study estimated how much low PA reduces life expectancy, and how much life expectancy could be improved by increasing PA levels for both populations and individuals.

Methods We applied a predictive model based on device-measured PA risk estimates and a life-table model analysis, using a life-table of the 2019 US population based on 2017 mortality data from the National Centre for Health Statistics. The participants included were 40+ years with PA levels based on data from the 2003–2006 National Health and Nutritional Examination Survey. The main outcome was life expectancy based on PA levels.

Results If all individuals were as active as the top 25% of the population, Americans over the age of 40 could live an extra 5.3 years (95% uncertainty interval 3.7 to 6.8 years) on average. The greatest gain in lifetime per hour of walking was seen for individuals in the lowest activity quartile where an additional hour’s walk could add 376.3 min (~6.3 hours) of life expectancy (95% uncertainty interval 321.5 to 428.5 min).

Conclusion Higher PA levels provide a substantial increase in population life expectancy. Increased investment in PA promotion and creating PA promoting living environments can promote healthy longevity.