Take Sarah Jenkins, 28, a runner who recently embraced the body-positive approach to fitness. "I used to run because I hated my body," she admits. "I’d track every mile and beat myself up if I didn't burn enough calories. Now, I run because I love what my body can do. I run to clear my head. The irony is, I’m more consistent now than I ever was when I was doing it out of self-hatred."