I know that it is trite to tout exercise, but it is worth mentioning that we keep learning more about its health benefits. I recently attended a talk on breast cancer in which daily exercise compared favorably with several widely-used chemotherapy protocols.
Humans were not designed to sit on their butts all day watching TV or reading ephemeral stuff on the Internets.
You name it, and exercise helps it, in the NYT by Jane Brody.