How much walking is good for your health? Yukitoshi Aoyagi, head of a department at the Tokyo Metropolitan Institute of Gerontology, says, "It's not as simple as saying the more you walk, the healthier you become. The Nakanojo Study, which tracked the entire lifestyle of approximately 5,000 residents aged 65 and over living in Nakanojo Town, Gunma Prefecture, not only the number of steps but also the intensity of walking, sleep, diet, and presen…