Studies show a strong relationship between a healthy body and a healthy brain. The brain has approximately 86 billion neurons designed to communicate to the rest of the body through chemical messengers called neurotransmitters. Studies show that deficiencies of two of these neurotransmitters (glutamate and gamma-amniobutyric, or GABA), can lead to mood disorders such as depression. However, regular exercise can increase the amounts of the two neurotransmitters, contributing to increased mental fitness.
When you're stressed, your brain secretes cortisol. It is known as the "fight or fight" hormone. Exercise is a good way to expose your body to "controlled stress," which helps regulate your brain's response to unnecessary stress, keeping you calm.
Your brain ages just like the rest of your body, but older adults who exercise have larger brain volumes than those who don't. Plus, the brain's hippocampus (which is responsible for memory and learning) is larger in those who are active.