The document discusses how aerobic exercise positively impacts brain health and cognition. It states that modest amounts of aerobic exercise can protect against brain atrophy and reverse typical age-related tissue loss. Exercise increases brain function and mass by creating new brain cells, blood vessels, and enhancing neuron communication. Walking just one mile a day can help prevent brain atrophy. Physical activity also reduces stress, improves mood, increases memory, and makes people smarter by reconfiguring the brain.