Dana is a former gymnast who developed an eating disorder at age 13, which she says went hand-in-hand with overexercising.  “We would get weighed before competitions, so the older girls taught me how to throw up my dinner the night before a competition,” says the 41-year-old yoga teacher, who lives in Dubai. “But when vomiting became difficult, I figured I could purge the calories by running, climbing stairs or using the step machine instead. I would