During the course of the year at Runner's World, as we cover elite runners, back-of-the-packers, and everyone in between, a few stories strike a chord with readers. This month, we’re following up with the subjects of some of our most popular stories from 2015 to learn what they're up to now. Here, Runner's World checks in with Derek Mitchell.

Stuffed inside a shoebox in Derek Mitchell’s bedroom in Kansas City, Missouri, are finisher’s medals and bibs from the 20 5Ks, two 10Ks, and half of a Tough Mudder he’s collected since March. In all, he completed close to 80 race miles—nearly 50 more than the 35-year-old set out to finish this spring. 

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“When I pick up the box, it’s really heavy,” Mitchell told Runner’s World. “It’s like a dream, like, did I really do all of this?” 

Mitchell first made headlines when Fox 4 News covered his last-place finish at the Big 12 Run 5K in Kansas City on March 14. Tailed closely by the chase car, he ran the last few meters to the finish line, crossing it in 1:27:44.

The race marked the beginning of his goal to complete a 5K each month for the remainder of the year.

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At the time, Mitchell weighed about 570 pounds, down from his heaviest weight of 625 pounds at the start of 2015. Five years earlier, he was diagnosed with prolactinoma, a condition where a benign tumor on the pituitary gland overproduces the hormone prolactin. This blocks production of testosterone, and a complication is weight gain. Medications have since addressed the problem, which motivated Mitchell to adopt a healthier, more active lifestyle.

Mitchell’s story resonated with the running community, so much so that he decided to create a Facebook page to chronicle his streak. It has since amassed more than 18,000 fans. 

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Tiffany Belt, 47, from Moberly, Missouri, was inspired by Mitchell’s pledge. An Army veteran and recovering addict, Belt was 100 pounds overweight when she first learned about Mitchell.  

“I was miserable and wanted to make a change, but I just never was able to find a place to start or the motivation to do so,” Belt said. “When I read several of the articles about [Mitchell], I thought, if Derek can get out there and do a 5K, I have no more excuses.” 

Belt reached out to Mitchell on Facebook, and the pair began regularly encouraging each other online. In June, they met up in person.

“Derek gave me the biggest hug,” Belt said. They walked every step of the Glow Run 5K in Kansas City together. “Derek is always supporting me when I post about my times or mileage and telling me he is proud of me. Truth be told, I am in awe of him. I frequently tell him he is my fitness hero.”

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Over the course of the year, Mitchell was invited to events all over the country, ultimately finishing races in seven states.

He dropped his time down to 1:10, which he notched at the Team RWB 5K in Independence, Missouri, this November. He also lost about 100 pounds from his original weight. 

Mitchell’s throng of supporters hasn’t made him immune to some lows, however. 

This fall, he regained about 10 pounds of the weight he’d lost, weighing 538 pounds at the end of November. At some races, he still finds himself in the same position he was in at the Big 12 Run 5K—dead last. 

“I’ve had moments where I don’t want to do it anymore, especially during the 10Ks,” Mitchell said. “At one, [the race organizers] said they didn’t care how long I took, but they started shutting everything down. After I hit the 5K mark, I had a police escort because they’d opened up the streets.” 

Despite the hurdles, Mitchell plans to continue his streak and work toward finishing a half marathon next year. (In June, he signed on for the Honolulu Marathon on December 13 but decided to defer his entry because of a minor knee injury.) His ultimate goal is to reach 400 pounds so he can start running more during races. To get there, Mitchell started working with a trainer who added strength exercises to his daily walking routine. 

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In return for the flood of encouragement he’s received online and at races, Mitchell said he hopes his story will inspire others in similar situations to take the first step toward living a healthier life.  

“I’ve talked to people online who are afraid to go to races because they’re afraid of what people will think,” Mitchell said. “But I’ve been the biggest out there—and I’ve been the slowest out there—and I’ve still experienced more support than I could’ve ever hoped for. I’m living proof that it is a possibility—and that it’s fun.”

This article originally appeared on RunnersWorld.com.