Meet the Real-Life Inspiration Behind Jillian Bell's Brittany Runs a Marathon

Brittany O’Neil has experienced two unique life changes in the last decade.

First, she decided to take charge of her health and trained for the New York marathon, shedding 60 pounds in the process and altering her career path. Second, her close friend and former roommate, writer/director Paul Downs Colaizzo, decided to write a movie about her experience.

That film, Brittany Runs a Marathon, is about to open in theaters.

O’Neil went from running zero miles to 26.2, and from a career in theater to one in human rights. She is still trying to wrap her head around the fact that the movie exists, that Jillian Bell (22 Jump Street) is playing the lead role inspired by O’Neil, and that she’s being interviewed about it.

“It’s super strange,” she tells PEOPLE with a laugh. What started as a fitness-oriented goal for O’Neil ended up being much more.

“I wanted more for myself and running was the way that it felt like the start of a change,” she explains, noting that those initial emotional and motivational beats in the film are very similar to what she experienced herself. “My first run was I think I two miles, not one block like in the film, and the gradual progress that every single time I could go a little farther or get a little faster was really sort of what pushed me forward and motivated me more.”

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Writer/director Paul Downs Colaizzo and Brittany O'Neil
Writer/director Paul Downs Colaizzo and Brittany O'Neil

Colaizzo, who is a longtime close friend and former roommate of O’Neil’s, told her early on that he wanted to turn her story into a film.

“We were roommates at the time and we were sitting on the couch,” O’Neil recalls. “I had already lost probably about 60 pounds at that point and I was training for the marathon. Paul had been a big part of my questioning where I was going in my life and wanting to make a change. He had been a good support system and a friend to me during that and we were hanging out watching Real Housewives or something, and he said, ‘So, I’m writing a movie about you.’ I said, ‘What is it called?’ He said, ‘It’s called Brittany Runs a Marathon.’ And I said, ‘How fast does she run it?’ And he said, ‘Ah, well I almost don’t want to tell you this, but she gets injured.’ It becomes about distance traveled.”

Coincidentally enough, O’Neil, who was healthy at the time of Colaizzo’s announcement, later tweaked an ankle while training that kept her “out of the marathon for two years,” she says. “He wrote it fictionally before that ever came to fruition in real life, which is totally wild.”

O’Neil says that the film’s heart and soul are very similar to her own experience, but that Brittany Runs a Marathon, which won the Audience Award at the Sundance Film Festival earlier this year, isn’t a biography — it’s only inspired by O’Neil’s story.

“The emotional journey is dead on. The fact that the character is her own protagonist and antagonist, I would say that that sort of struggle throughout, he captured that perfectly,” she says. “And the journey of wanting more for yourself, wanting to change. But I was working in theater, I wasn’t working at a box office like in the film. I was running an off-Broadway theater company at the time, so there was some level of having it together.”

Jillian Bell in Brittany Runs a Marathon | Amazon Studios
Jillian Bell in Brittany Runs a Marathon | Amazon Studios

O’Neil has high praise for Bell, who plays the fictionalized Brittany.

“I’ve always loved her work but I didn’t want to meet her towards the beginning. The character is Paul’s creation and she had to find her own interpretation of it,” O’Neil says of wanting to wait to meet Bell. “I did go on set a couple of times and have a really short cameo, on a street corner and in one of the running shots. And so I met her a couple times during filming and since then we’ve gotten coffee and chatted a lot and I adore her. I feel forever connected to her through this movie. She nailed it so well that I feel like she knows me extremely intimately because of how she portrayed this character.”

O’Neil also wants people to know that she still struggles with her own insecurities and issues that initially motivated her to run a marathon to begin with.

“I think it’s important to know that it’s not like the story’s over like, ‘You did [the marathon] and now you’re done.'” It’s still a constant struggle for me,” she admits. “I’ve made huge strides, especially because I’ve had to identify my feelings about this knowing that I would have to talk about it. And so in that way, I’m really grateful for this whole experience because it has brought me so much more progress than I think I ever would have made. But it’s definitely strange to have to do it.”

Brittany O'Neil | Vivien Killilea/Getty Images
Brittany O'Neil | Vivien Killilea/Getty Images

O’Neil has happily settled into a new career in human rights.

“I work for an organization called the International Rescue Committee resettling refugees in New York and New Jersey,” she says. “That has brought me a lot of clarity as far as what matters and knowing that my work is impacting a broader community.”

And is she still running?

“When I was in the thick of it, I was like 60 miles a week. I think my sweet spot was at like 35 miles a week,” O’Neil says. “And now, I don’t run a lot because, even actually as we speak I’m wearing an ace bandage. I have tendonitis, it sort of flares up here and there. So I try to keep it to no more than two to three miles at a time.”

Brittany Runs a Marathon opens in select theaters on Friday.