I thought this was awesome so I wanted to share it! Even in such a short time, I'm finding that it's really accurate.
See Julia Run: Benefits of Running
Most serious runners will say their addiction goes beyond the physical benefits they achieve from running. Runners say the intense exhilaration and euphoria that comes after a run is what motivates them most. In fact, this euphoria comes from a betaendorphin release triggered by the neurons in the nervous system. Intended to alleviate the pain after a run, it creates a feeling of extreme happiness and exhilaration. Runners become addicted to this intense high, and it can often replace other addictions to drugs, alcohol, and even food. While runners claim to achieve more energy in daily life from running, it also helps bring appetite, exercise and food into balance. Furthermore, as running makes the body function better, it improves sleep, eating, and relaxation.