Ben Dempsey hated running. Growing up, he dreaded the one-mile runs in gym class.

As an adult, he never ran — and avoided all other forms of exercise. By 27, his weight soared to 360 pounds. He was diagnosed with high blood pressure.

That’s when he turned to running to change — and save — his life.

On Sunday, Dempsey will attempt to run 26.2 miles in the Publix Georgia Marathon and Half Marathon, his first marathon.

About 18,000 runners are expected in the field, with slightly more than half opting for the half-marathon.

“For me it’s the completion of a journey that I started two years ago,” said Dempsey, who lives in McDonough. “This journey is nowhere near done.”

The Publix Marathon (formerly the ING Marathon until two years ago) is popular for its scenic route as well its timing around spring. The course winds through some of Atlanta’s most historic and picturesque neighborhoods, including the Sweet Auburn District, Inman Park and Decatur. Along the way, runners will pass the King Historic Site, the Carter Center and Piedmont Park.

Other upcoming runs include the Zooma Atlanta Half Marathon at Lake Lanier on April 22, and the Race for the Fallen at Red Top Mountain Half Marathon in Cartersville on Sept. 15. On Nov. 3, Savannah will host the Rock ’n’ Roll Marathon & Half Marathon. The Atlanta Half Marathon and 5K are scheduled for Thanksgiving Day.

Registration for the lottery for The Atlanta Journal-Constitution Peachtree Road Race 10K on July 4 is open through Thursday.

The interest in marathoning has steadily risen. The number of marathoners in 2011 jumped to a record high of 518,000, according to Running USA, a nonprofit organization for the running industry.

About 7 million Americans run at least three times a week, according to a 2010 survey by the National Sporting Goods Association.

About three years ago, Dempsey said he was tired of not having energy or motivation. He’d quickly break into a sweat and get winded from playing ball in the backyard with his then-9-year-old son, Chris.

Since 2009, Dempsey has lost 165 pounds. He started with a dietary plan of his own design. The first step was eliminating all soda. (The 29-year-old was drinking as many as 10 20-ounce-bottles of Coke or Mountain Dew every day.) And then he started running, following the run/walk interval training program by former Olympian Jeff Galloway. In September, Dempsey started running/walking four miles some days, eight miles on others. He rests two days a week.

Also taking part in the Publix-sponsored event is Kari Cernoch, who enjoys running — but not too fast.

“During longer races — marathons and half-marathons — I run between 9- and 10-minute miles. Fast enough for me to have fun while I run,” she said.

The elementary school teacher has completed one marathon and six half-marathons. She’ll run the half-marathon Sunday.

“I had a great time during my first half-marathon, although I didn’t think I could run that far,” said Cernoch, who lives in Atlanta. “I realize ... if you think you can do it, you probably can.”

Cernoch’s workout routine and training schedule often blend together. In January, she started incorporating a long run of as much as 13 miles on a weekend day to get ready for the race. She continued to run between two and five miles on Tuesdays, Wednesdays and Thursdays.

On race day, she’ll stay hydrated and try to enjoy the race. If she has to stop and walk a little, that’s OK, too, she said.

Meanwhile, Dempsey, within 15 pounds of his weight goal, loves running.

“I get out there and enjoy it. It takes me away from the world and it’s a good feeling. And I get that runner’s high,” Dempsey said. “And after that run I feel that sense of accomplishment.”

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Upcoming races

Sunday: The Publix Georgia Marathon and Half Marathon

April 22: Zooma Atlanta Half Marathon at Lake Lanier

July 4: The Atlanta Journal-Constitution Peachtree Road Race 10K

Sept. 15: The Race for the Fallen at Red Top Mountain Half Marathon in Cartersville

Nov. 3: The Rock ’n’ Roll Marathon & Half Marathon in Savannah

Note: For more information, go to www.rungeorgia.com.