“BRITTANY RUNS A MARATHON”

**

(R, 1:43)

The supposedly feel-good comedy “Brittany Runs a Marathon” aims for more of a runner’s high than joyful indulgence. You may feel miserable while watching it, but the goal is to feel stronger when it’s over.

When her story takes off, Brittany (Jillian Bell) is joking her way through a rut. She rushes for a train she always misses and goofs off during a disciplinary meeting at her job. She attends a doctor’s visit hoping to get a prescription for Adderall, but her appointment veers off course when she is instead told her lifestyle is putting her health at risk. Her heart rate and blood pressure are high, and so her doctor recommends that she lose around 50 pounds.

For Brittany, who sleeps until noon and drinks all night with her judgmental roommate Gretchen (Alice Lee, in a thankless role), the diagnosis is unthinkable; it would require Brittany to change her entire life. But she does, one agonizing step at a time.

Brittany starts running to avoid having to pay for a gym membership. As she builds her endurance, she meets new friends, Seth (Micah Stock) and Catherine (Michaela Watkins), who encourage her attempts to grow. With them, Brittany trains to run the New York City Marathon.

But for every sign of success, Brittany is plagued with self-doubt; for every offering of kindness, she is overcome with suspicion. The writer and director Paul Downs Colaizzo follows Brittany’s training, focusing less on the challenge of running than on the psychological barriers that impede physical achievement. As Brittany nears her goals, she lashes out more and more against those who seem to affirm her self-worth. She alienates Seth and Catherine when they offer financial support, and outright rejects the dopey affections of Jern (Utkarsh Ambudkar), a sweetly rootless millennial who hits it off with Brittany in the middle of her transformation.

Brittany’s kneejerk self-deprecation often feels punishing not only to the character but also to the audience. Bell imbues Brittany with humanity and wit, but all too frequently she is working within the framework of a story that seems hellbent on robbing her character of joy.

Likewise, the bouncy mood set by the movie’s bright colors and zippy one-liners is cut down to size by the less humorous cruelty thrown Brittany’s way — and by the cruelty she shows to herself and others. And while there are references to bodies being beautiful at all sizes, there’s no suggestion that her mental health might benefit from the same attention given to her physical health. Perhaps running can’t treat both at the same time.

The best thing that can be said for “Brittany Runs a Marathon” is that it does make long-distance running seem achievable. After all, if Brittany endures such unrelenting emotional anguish on her way to the starting line, how bad can the physical pain of a marathon be?