Although the quality of white matter, which is responsible for providing fast and efficient nervous connectivity throughout the brain, appears to improve with increased physical activity in adults, this area of research in children is in its infancy. For instance, excess body weight has been linked to poorer white matter, but whether daily physical activity (e.g., play) and sedentary behavior (e.g., watching television), both of which can affect body weight, are associated with white matter quality during childhood is poorly understood. As such, this study’s investigators examined the associations of physical activity and sedentary behavior with white matter (assessed by magnetic resonance imaging) in more than 100 children with overweight or obesity. More active children were found to have healthier white matter than less active children. In addition, the amount of time watching television was associated with poorer white matter health. These findings are consistent with a growing body of scientific literature indicating that an active lifestyle is positively associated with brain health across the lifespan. These outcomes should inform public health policies aimed at increasing physical activity and reducing sedentary behavior in children.