" Of the various factors that make osteoporosis a modern mismatch disease, one of the biggest is physical activity, whose beneficial effects on bone health are difficult to exaggerate. First, because the skeleton mostly forms before one’s early twenties, lots of weight-bearing activity during youth—especially during puberty—leads to greater peak bone mass. As figure 26 graphs, people who are sedentary when they are young commence middle age with considerably less bone than those who were more active. Physical activity also continues to affect bone health as people age. Dozens of studies prove that high levels of weight-bearing activity considerably slow and sometimes even halt or modestly reverse the rate of bone loss in older individuals. "

― Daniel E. Lieberman , The Story of the Human Body: Evolution, Health, and Disease