Rosie Coates sees all kinds in her line of work: stickup artists, drunk drivers, streetwalkers, and drug dealers. As a King County corrections officer, Coates keeps the peace five days a week in the downtown Seattle hoosegow. She doesn't pass judgment on those living on the wrong side of the bars. "We all make choices on how to live our lives," she says.

Seven years ago, at the age of 34, Coates was a prisoner in her own 300-pound body. Coates knew her own choices had put her there. She'd deprived her body of exercise and devoured double portions of fast food. "I've always struggled with my weight," says Coates, who stands six feet tall. "When I was young, my grandmother would give me food and candy, so I associated food with the kindness and love that she gave me."

Coates attempted to get in shape in 1987 after giving birth to her daughter, Ebonee, and then again in 1997 when she had to pass a physical agility test for her job. But the healthy habits never stuck.

Things came to a head in March 2002. Coates's husband, Ron, and Ebonee, then 15, were away at a high school basketball tournament. Coates sat home alone binging on burgers and fries, moribund and miserable. "I had been raising Ebonee to take care of herself, and I realized I wasn't doing the same for myself," Coates says. "I finally got tired of being sick and tired. I decided to take control of my life. I decided to get strong."

Today, at age 41, Coates embodies the strength she once sought. She shed 110 pounds the old-school way (eat less, sweat more) and became a marathoner. But she wasn't content to stop there. She wanted other women She Raced 18 Horses in an Ultramarathonand Won Sporty Diva with the mission of helping other women find the attitude, strength, and determination to change their lives.

Coates's transformation started with her diet. She put herself on a 3,000-calorie-a-day plan, down from 10,000. "I made better choices, snacking on fruit instead of Snickers bars," she says. "I only went to restaurants that had nutrition information available." She joined a YMCA and started walking, then jogging for five minutes, then 10, then 20. "It was a little shocking," Coates's friend Anita Smith recalls. "She started working out five days a week. I mean she didn't miss a day."

Coates's dedication got results: She lost 100 pounds in 18 months. And she found a new identity. "I realized I wasn't a jogger," Coates says. "I was a runner."

A hard-core one at that. Coates's shift starts at 6:20 a. m., and she lives 43 miles away, and catches a commuter bus at 4:45 a. m. So when she logs six miles before work, she's doing it at 2:30 a. m.

During the fall of 2004, Coates set her sights on running a half-marathon. "I started running a consistent five, eight, 10 miles," Coates says. "It became an addictive thing for me. My ego totally rocks when I'm in motion—I feel healthy, empowered, happy, sexy, and vibrant."

Coates ran 10 half-marathons over the next four years, and word got around. "Folks at the Y asked me to train them," she says. So Coates became a certified trainer and fit a few clients in between her job and her own workout schedule.

Now she gives three-hour "Healthy, Fabulous, and Fit" workshops in the Seattle area that attract women like herself, often working mothers who want to get fit. "Rosie's a great motivator," says Danielle Woodbury, who's lost 31 pounds since she started working with Coates in 2008. "She's so positive, but she doesn't mess around—she kicks you in the butt."

And Coates continues to push herself. Last November, she ran the Seattle Marathon in 5:48. In March, she cut nine minutes off her time at the Whidbey Island Marathon, and in May she ran the Tacoma City Marathon in 5:06. Her next goal: Beat five hours. She'll take a crack at it this fall at the Portland Marathon (October 4) and the Seattle Marathon (November 29). "When I get to five hours," she says, "then I'll do an ultra!" It may take years of 2:30 a. m. treadmill runs to get there. But don't bet against Coates. She's busted out of her old body and she ain't going back.

"I'm a better mother, wife, and employee," says Coates. "I now have confidence that when I set a goal, I can accomplish it."