For style-conscious theatergoers, the unexpected benefit of The Whale at Theatre Exile is that you come out vowing never to eat again. Less happily, you also discover why the word morbid is coupled with obesity in the story of a guilt-ridden gay father who is eating himself to death, one KFC bucket at a time.

So, it's not a great date night. But the compelling, provocative Samuel D. Hunter script is the showcase for a well-honed production directed by Matt Pfeiffer in which some of Philadelphia's best actors surpass themselves.

Assuming you can take it.

From the beginning, the obese Charlie (Scott Greer) has chosen one of the worst-possible deaths: an end-stage addiction with nothing so comforting as denial or intoxication. His rage-a-holic daughter provides extreme degradation. Though Charlie turns out to be the loveliest of spirits and a deeply poetic soul, he is automatically invalidated on every level by his obesity. The message that comes at him from nearly every side is that the obese aren't human - a conclusion drawn in the company of a man whose only repose comes from constantly apologizing for himself.

The play's basic premise has its contrivance, set in the Mormon country of Idaho where a guilt-ridden gay male couple had a bad time of it. One guy starved himself to death before the play started; the other, Charlie, is now 600 pounds, but he deprives himself of the money he earns as an online English professor to provide for his daughter from his earlier union. Both ex-wife and daughter despise him. His caregiver despises them back. Then a Mormon missionary wanders into the fray.

Oddly, they all simply want to do one indisputably right thing in their lives. Literary overtones from Moby-Dick and the Old Testament story of Jonah have more than whales in common; they are tales of people turning toward and away from God. Laudably, those pieces don't fall neatly into place, leaving the audience with many ways to connect the dots.

Though Greer has been a bit self-regarding in past roles, none of that is found in his performance of a man suffocating from his own fat for most of the two-hour, intermission-less show. Despite the innate physical restrictions of his character, Greer gives a rich, varied performance with furtively darting eyes and a voice that's authoritatively professorial but that also accommodates the meekness of emotional desperation.

As his mentally disturbed daughter, Campbell O'Hare is convincingly abrasive, almost too much so, forcing you to find her humanity without much help from her - but recognizing how much her intelligence has led to an empty life in a landscape where the only relief is TV and marijuana, turning her into a seething mass of nothingness.

Kate Czajkowski wears her contradictions lightly in the role of the caregiver, since bringing Charlie high-fat food and haranguing him to go the hospital has little apparent inner conflict. She has her mission and sticks to it. Trevor William Fayle plays a card-carrying missionary with magnetic sweetness.

One complaint: If you have come to love Greer's character, you want a scene somewhere - a fantasy or flashback - with him liberated from the self-imposed, life-sentence imprisonment in his body. Am I being sentimental?

The Whale

Through March 1 at Theatre Exile at Studio X, 1340 S. 13th St.

Tickets: $10-$40.

Information: 215-218-4022 or www.theatreexile.org.EndText