Overview: Brittany Forgler is a hilarious, friendly, hot mess of a New Yorker who always knows how to have a good time, but at 27, her late-night adventures and early-morning walks-of-shame are starting to catch up to her.

When she stops by a Yelp-recommended doctor's office in an attempt to score some Adderall, she finds herself slapped with a prescription she never wanted.

Forced to face reality for the first time in a long time, Brittany laces up her Converse and runs one sweaty block.

The next day, she runs two. Soon she runs a mile. Brittany finally has direction, but is she on the right path?

Verdict: It's not often that your best friend writes and directs their debut feature film about you, but Brittany O'Neill's mental and physical transformation inspired her friend/writer/director Paul Downs Colaizzo to make 'Brittany Runs a Marathon,' a drama disguised as a comedy about the hard work of changing yourself.

Comedian Jillian Bell steps into her first starring role as the funny, frumpy Brittany, a New York City party girl/slacker whose body can't keep up with her arty all day/sleep all night routine (Bell also produced the film). Under doctor's orders, she hits the pavement in search of salvation.

And along the way, she finds herself.

The ending is right there in the title, but Colaizzo's film leans into the old adage that it's all about the journey, not the destination, following the achingly hard work of Brittany's trek toward the finish line of the New York City Marathon, and ultimately, toward happiness.

Brittany's problems aren't unique, and they aren't insurmountable, but they aren't easy. She's got a lame job, flounders in her love life, grieves the loss of her father and has high blood pressure to boot.

Living with a wannabe influencer, Gretchen (Alice Lee), isn't the best influence either. But for all her external problems, the highest mountain Brittany has to climb is getting over herself, a struggle Bell makes poignantly, piercingly real in her performance and that takes the film into its darkest yet most relatable moments.

To anyone who can relate to Brittany's predicament of feeling stuck and depressed, this may all sound familiar. She's unable and unwilling to receive and accept help and love from her loved ones, so she wallows in her own bad thoughts and negative spirals.

During a particularly nasty relapse, while recuperating from an injury at her sister's home, a drunk Brittany spews all her judgmental thoughts (clearly about herself) at another plus-size woman, envious that this person has decided to choose happiness and joy in her own body rather than self-hatred.

It's an ugly moment, tough to watch, and Bell and Colaizzo don't shy away from the darkness.

Colaizzo has stacked the cast of this dramedy with gifted comedians alongside Bell, including Michaela Watkins, Utkarsh Ambudkar and Lil Rel Howery, who all bring a natural levity. But the script also offers each performer a meaty dramatic arc.

Bell demonstrates her otherwise-unknown dramatic chops, and her performance is surprising and nuanced, yet also incredibly funny when it needs to be.