Brittany Runs a Marathon is a 2019 American comedy film written and directed by Paul Downs Colaizzo, in his directorial debut.

[3][4][5] It stars Jillian Bell, Michaela Watkins, Utkarsh Ambudkar, Lil Rel Howery, and Micah Stock.

She and her roommate Gretchen, a teacher's assistant dreaming of social media fame, are hard partiers who abuse drugs.

Visiting a new doctor to score an Adderall prescription, Brittany receives the unwelcome diagnosis that she is overweight and must get healthier.

After another night of partying by Gretchen, Brittany joins the group run and meets Seth, another struggling runner, learning they have equal goals.

Distraught, convinced she will gain back her weight, Brittany returns to the dog-sitting house and discusses the state of her life with Jern.

That same day, she disrupts Demetrius's birthday party by making comments about an overweight female guest due to her own insecurities.

Catherine reveals that running was a distraction from her nasty divorce, explaining that a year ago, she broke her wrist and was prescribed Oxycodone; her husband used it as evidence she had relapsed into drug use, and the court denied her visitation rights to their children.

Colaizzo wanted to emphasize the inspirational side of the story and take what would usually be treated as a fat sidekick stock character and instead explore her feelings and perspective.

[7] The real life Brittany had gotten into running but it was after Colaizzo came up with the film concept that she was inspired to try the take on the New York marathon herself.

[6] Tobey Maguire's production company Material Pictures, picked up the film based on the oral pitch.

In November 2017, it was announced Jillian Bell, Michaela Watkins, Utkarsh Ambudkar, Lil Rel Howery, Micah Stock and Alice Lee would star in the film, with Paul Downs Colaizzo directing from a screenplay he wrote.

The site's critical consensus reads, "Brittany Runs a Marathon is an earnest and hilarious dramedy that finally gives Jillian Bell a role worthy of her gifts.

[9] Dennis Harvey of Variety magazine wrote, "This terrifically engaging debut feature by playwright Paul Downs Colaizzo is the best kind of "crowdpleaser": one that earns every emotional beat that might seem formulaic in four out of five similar enterprises.