Physical Activity and Public Health for Adults: Is the Glass Mostly Empty or Half Full?

Early observations that only a small proportion of U.S. adults were engaging in enough aerobic physical activity to provide substantial health benefit helped shape our public health messaging for physical activity. This messaging has consistently indicated that most adults should increase their activity levels. However, it has been difficult to accurately estimate the proportion of adults who engage in sufficient levels of aerobic activity in the population, with survey-based estimates ranging from 22% in 1994 to 54% in 2018 and widely differing estimates from device-based measures. Recent accelerometer-based studies of physical activity and mortality risk provide new evidence that at least 50% of U.S. adults engage in enough aerobic physical activity to be at low risk for premature mortality. We argue that this observation should lend greater confidence to our current survey-based surveillance estimates, which indicate that a large proportion of adults is physically active. This new insight may also provide clues that could further strengthen our public health messaging for physical activity by placing more emphasis on the maintenance of healthy activity levels throughout life and possibly by using descriptive social norms as an additional intervention element-while continuing current efforts to encourage the adoption of healthy activity levels for less active adults in the population.