Most people have no idea how utterly true this statement is. Reading utilizes a specific set of cognitive skills that are strengthened over time. It is a skillset distinct from that which is used during other activities, such as exercising and watching a video.
As a result, it changes the brain over time. Our brains are a product of our behavior patterns.
I would highly recommend reading “What the Internet Is Doing to Our Brains,” by Nicholas Carr. He writes in-depth about research surrounding this topic.