When Kristy Oden began running more than a decade ago, her goal was simple and superficial.

She wanted to lose the baby weight.

The now 50-year-old had just given birth to her last child when she slipped into running shoes and headed outside.

Fifteen years and thousands of miles later, Oden has a new goal in mind. She wants to commemorate her 50th birthday with a 50-mile challenge.

Oden is registered for the American River 50 Mile Endurance Run on April 6 in Sacramento. In running circles it’s known simply as the “AR50,” a menacing name for a race billed as the second-largest 50-miler in the United States.

“Now it’s my turn,” said Oden, who has served as a pacer in years past. “I want to do it.”

This goes without saying: Don’t doubt her.

Running has become her life’s passion – her hat at the Jed Smith Ultra Classic on Feb. 2 read: “Kick asphalt” – and the surest sign of that is fast-approaching.

Her training for the AR50 will also include the Modesto Marathon on March 24.

The Manteca native is part of the volunteer group that founded the Modesto Marathon and Teens Run Modesto program.

The two programs share a symbiotic relationship, supporting one another.

The Modesto Marathon funds the program for at-risk teens, which in turn trains, motivates and encourages its participants to run the marathon.

“I heard about that and wanted to volunteer,” Oden said.

What began with small meetings in the summer of 2009 has now blossomed into a 4-year-old event that has grown in size and notoriety.

More than 2,400 runners have registered for the marathon, half marathon and 5-kilometer races.

Most are attracted by the challenge, but the serious and swift come from all corners of the map because the marathon is 1) flat and relatively fast and 2) it’s a Boston Marathon qualifier.

The marathon’s popularity, Oden says, has mirrored the running craze sweeping the valley.

“I’m just amazed at all the new people we see every year and the people who continue to run,” Oden said. “Every year, there’s more and more. Just running around Manteca, I see more people on the road or running the bike path.”

Oden is the bookkeeper for the marathon and Teens Run Modesto program. She not only balances the bank statements, but prepares financial reports for their monthly meetings.

 “Everyone does this on their free time. She comes over after she’s done with work,” Modesto Marathon director Heidi Ryan said. “She’ll come over from 6 to 8 at night and get us all caught up.

“She’s been doing this a few years now, so she understands the way things need be categorized. She’s developed it from the beginning to now. Before, I’d throw receipts at her and we’d have to wing it.”

Like the accounting, Oden has matured as a runner.

She’s completed 15 marathons and an ultra-marathon, with a pair of memorable book-end performances.

Her first marathon just so happens to be her fastest 26.2 miles. She completed the 2000 California International Marathon in Sacramento in 4 hours, 32 minutes.

Oden returned to the CIM on her birthday last year, determined to set a new personal record.

She came close.

Pelted by rain and bullied by the wind, Oden crossed the finish in 4:34.

Running, she says, has become addictive. It’s changed her life in ways she could never have imagined.

As for the baby weight?

She’s left that in dust, too.

“For me, it’s the socialization. When you’re out there and running with people, we talk,” she said. “And then you always have that good feeling afterwards.”