She began exercising one day in 2010, a 250-pound coed jogging around the campus at Salisbury University. “It wasn’t a pretty sight,” Kelly Sorensen said. “People made fun of me, shouting, ‘Run, Forrest, run!’ But I didn’t give up; it’s not in my DNA.” Seven years later, she’s still at it. On Saturday, Sorensen — now a trim 125 pounds — will compete in two races in the Baltimore Running Festival. At 7:30 a.m., she’ll run the 5K; two hours later, the 27-year-old New Windsor woman will tackle her 10th half marathon. Both times, as she crosses the finish line, her headphones will play the song “What A Wonderful World,” by Louis Armstrong. It’s her mantra. “I am a runner,” she said. Want proof? The Runner’s Prayer is tattooed on her ribs: “Run by my side; live in my heartbeat; give strength to my steps.” Last year, she ran the Marine Corps Marathon, her first, completing the race in 5:50:36. That Sorensen has made such strides in life boggles her mind. “Sometimes I think it’s unbelievable where I’ve come from,” she said. “If you’d told me back then how tiny I’d be, or that I could run 26 miles, I’d have laughed in your face.” Lloyd Fox / Baltimore Sun Kelly Sorensen, 27, of New Windsor. Kelly Sorensen, 27, of New Windsor. (Lloyd Fox / Baltimore Sun) If you’d told me back then how tiny I’d be, or that I could run 26 miles, I’d have laughed in your face. — Kelly Sorensen Once, Sorensen wore size 16 pants; now, she’s size 3. She can fit both of her legs into one leg of her old jeans. “Friends I knew then can lift me up now. Before, they wouldn’t have tried,” she said. “Kids at Liberty High School made fun of me being overweight; I wasn’t the girl guys came up to. Funny, now those guys feel the need to talk to me.” Back then, Sorensen concedes, she hardly helped herself. “I hated running,” she said. A catcher on Liberty’s softball team, she would excuse herself from those pregame jogs around the field, saying, “Sorry, coach, I’ve got to warm up the pitcher.” In college, homesickness and the stress of studies triggered eating binges. “I sat in my dorm room and ate chips all day,” said Sorensen, who gained 50 pounds in one year. Then a physical exam brought troubling