Pincock, who joined L.A. Weight Loss in April 2006, completed a 5k race – something she could never have done at 301 lbs. – last June. "It was exhilarating," she says. "I never dreamed I would do it – and I would do it again, if only to show my kids that they can do it, too."
See more amazing transformations in this week's PEOPLE, on stands Friday!