[NOTE: An official selection of the 2019 Seattle International Film Festival]

Not unlike many a comic actress before her, Jillian Bell is rather an acquired taste. Not everyone will appreciate her sharp-edged, forward-thinking, unscripted brand of humor that’s lent itself to a series of poorly chosen supporting roles. And yet, perseverance seems to be the keyword. For all the less flattering scripts one agrees to help in realizing (save for 22 Jump Street and portions of Office Christmas Party), something spectacular is sure to spring up. In Britney Runs a Marathon, Bell finds that opportunity in a heartfelt dramedy playing an aloof New Yorker striving on personal growth and improvement. All while training for the tri-state area’s single-largest athletic event all year. A rather monumental task, and yet Bell makes it look easy, alongside first-time writer/director Paul Downs Colaizzo making an unexpectedly dazzling debut.

Brittany Forgler (Bell) is considerably not a fully-functioning/contributing member of society in the big apple. Age 28, working as support staff at an off-Broadway venue, her self-esteem low, her weight a bit on the heavy side, and a bit of an addict (on food, drink, and Adderall) to fill the empty spots. The social repercussions are enough to convince her a serious lifestyle change must hit, and quickly. Her persistent discipline issues are challenged to an extreme the moment she takes up jogging in her spare time, with her white whale of an elusive goal in sight, to eventually run the 26-mile New York City Marathon. It’s an 18-month journey Brittany must prepare for, both mentally and physically. Luckily, she won’t go it alone, aided by other amateur runners, like embarrassed dad Seth (Micah Stock), and jilted divorcee Catherine (Michaela Watkins).

If that were the whole film, with plenty of raw, favorable gags scattered about, I’m sure I’d have stayed invested, albeit with a minor shred of emptiness in my stomach. And yet, Colaizzo, making a seamless transition from writing for the stage, pulls a deliberate lateral from not shying away from Brittany’s own transition, and to a smaller extent, that of Bell’s, who lost 40 pounds during the filmmaking process. It’s all versed in truth, Colaizzo having known a friend named Brittany during his younger adult years, so at least parts could be considered autobiographical. No level of intense training could gear Brittany up for the more emotional, personal, bitterly melancholic elements of her evolution as a person. Her cockiness, her unabashed partier motives are a clear mask for her years of built-up insecurity, lack of insecurity, and occasionally unfiltered negativity toward those around her. And those broadly secretive segments of her psyche are greatly exposed, leaving nothing on the table.

Bell excels at every stage, keeping her wittiness at a large wavelength that it isn’t forgotten. Yet her ability to pivot with the swing of Brittany’s emotional range is its own wonderful surprise. Not once would I have expected such clarity out of an otherwise crass, loud, not entirely offensive actress. Leave it to Colaizzo to really bring out Bell’s gentler, far more vulnerable side, and then some. It’s like it isn’t the first time we’re such tenderness out of her, even though for some it will be. Sword of Trust, her other big film this summer, was certainly a step in the right direction working under the wings of Marc Maron and Lynn Shelton, but despite also being a favorite of SIFF audiences, it won’t have reached a similar level of potential patrons as Amazon is granting here. Marathon helps to gravitate Bell to a new level of performance with a more appropriate market share.

While she does command the screen throughout, her supporting staff needn’t be overlooked, especially those there to give Brittany the best leg-up. Watkins and Stock are absolutely hilarious when the trio buddy up, neither of them as flawless as the other, they each carry some personal baggage they’re trying desperately to drop. And that, in turn, will propel their screen presence in high regard. There’s Brittany’s annoyingly skinny roommate Gretchen (Alice Lee), an abrasive deterrent from her goals, chiding her constantly. There’s the slightly shoehorned love interest (Utkarsh Ambudkar), a competing pet-sitter with whom a war of words and eventually hesitant physical expression builds. But perhaps the best little secret is the ever-reliable Lil Rel Howery as the brother-in-law, and the stern voice of reason who’s still a bit of a big kid but knows when to put the foot down.

Anyone going into this movie expecting the typical R-rated mid-year light-hearted piece of comic filmmaking, I have no doubt Brittany Runs a Marathon will surpass that studio criterion. And yet, Colaizzo will do more than surpass, making the marathon its own psychological plot device, where our titular hero is essentially racing to defeat the only competitor that matters: her crippling sense of self-worth. There may’ve been a bit too much of her own deprecation scattered about, and the reprieve may tire itself out at the end. But Bell doesn’t see that to be much of an issue. We know she wants to change her life; it may be played with an excessive toughness. But when she allows herself to really embrace happiness in her life, that’s when things really click. It’s that balance between self-doubt and self-acceptance really driving Brittany to her, and its finish line, even as the physical pain becomes impossible to bear. At one point, it does; like many a physical challenge, however, it’s best to soldier on. Bell and Colaizzo accomplish just that, making it compelling, approachable, and somehow soul affirming. I’ll be down to feel the burn, the gasps, and the rib-tickling on this one again soon, assuredly. (A-)

Brittany Runs a Marathon opens in Seattle (SIFF Egyptian) and Bellevue (Cinemark Lincoln Square) today, wide release September 13; rated R for language throughout, sexuality and some drug material; 103 minutes.