Worldwide, a person is diagnosed with dementia every three seconds. Regular physical activity and limited sedentary behavior (i.e., time spent sitting or lying down) are two important lifestyle strategies for maintaining good brain health. However, we do not know which of these affects the brain more. In this study, investigators examined the relationships of physical activity and sedentary behavior with brain cortical thickness using advanced imaging. Thinning of the brain’s cortex is common with aging. In 30 community-dwelling older adults, higher physical activity, but not sedentary behavior, was associated with greater cortical thickness in regions that are linked with cognitive decline. Importantly, higher physical activity was associated with greater cortical thickness even after accounting for time a person spent sitting. This suggests that being physically active shields the brain from the consequences of sedentary time. So, what are the recommendations for older adults who want to maintain or improve their brain health? Keep moving! Meeting the current physical activity guidelines of 150 minutes per week of moderate-to-vigorous-intensity physical activity is a key step to maintaining a healthy brain.