Brittany O’Neill was one of millions of millennials who was flailing through life amid an uncertain job market, divorced parents and a lack of purpose for their lives. At 28, she was drinking way too much way too often, allowing herself to be used by random guys, and working a job that didn’t offer enough money to build a future.

Remarkably, she turned it all around by first finding the will power to run around the block in her rundown New York City neighborhood. How she took those terrifying tentative first steps and wound up running in the New York City Marathon forms the heart of the terrific new movie and Sundance Film Fest sensation “Brittany Runs a Marathon.”

Played by rising comedy actress Jillian Bell, who lost 40 pounds herself in taking on the transformative role, the movie opens with Brittany at a stunning low point.

She works a low-paying, low-responsibility job at a live theater. Her snobby roommate drags her to nightclubs every night, yet constantly derides her as being a fat, lonely loser. She’s promiscuous, with no self-esteem and drinks way too much.

When Brittany gets a medical checkup due to feeling bloated and miserable, he tells her she has fatty deposits on her liver and is at risk of an early death if she doesn’t stop drinking and lose weight. She is scared straight by this diagnosis and wants to change, but she doesn’t even know how to begin until she meets a young gay married man in a runners’ club.

His friendliness inspires her to reach out for help which he readily gives. Brittany is also befriended by a concerned neighbor named Shannon (Jennifer Dundas), who overcame heroin addiction in her 20s and wants to inspire her.

At first, Brittany’s efforts seem comically futile, as she can barely make it around a city block while running. But as she’s joined by her two friends, she starts running further and stops drinking and sleeping around. They eventually set a goal of running the New York City Marathon together.

Another big change happens when she lands a housesitting job at night yet discovers a male slacker is doing the day shift and has actually moved into the house. At first they clash, but then they become good friends and eventually lovers as Brittany learns to trust him and open up about her life.

Meanwhile, her old roommate sees her and is shocked by her improvements. Brittany just keeps moving forward, but when she experiences a serious injury just weeks before the marathon, her plans are thrown for a loop and she has to decide if she can maintain the strength to continue improving herself or if she will backslide into self-destruction.

Based on a true story, in which the real-life Brittany lost more than 50 pounds, “Brittany Runs a Marathon” is incredibly inspiring and a “Rocky” for our times. Its writer-director Paul Downs Colazzo wisely ties together the many issues that poor self-worth affects.

Its star Jillian Bell underwent a remarkable transformation of her own throughout the movie, losing over 40 pounds as she depicted Brittany’s efforts. It’s a rare feat during a movie shoot, especially for actresses, and adds power to her performance.

Colazzo and Bell team up to make the movie equally funny and uplifting, while also making its sadder moments deeply affecting. The supporting cast are also vibrant additions to the movie.

The movie shows that millenials raised in broken homes and without much moral guidance can become tragic messes in adulthood. Yet it also shows that anyone can strive to overcome their circumstances and be better. n

“Brittany Runs a Marathon”: A