LOS ANGELES — Smoked fish for Jeff Garlin is one big bowl of tasty. At least that’s what he implies while he sips a milkshake (his version of “a salad”) as we chat at a Jewish deli one morning in the Los Angeles neighborhood of Studio City, a haven for working actors and comedians just north of the Hollywood hills.

“I just ordered the lox platter,” Mr. Garlin says, looking trimmer than his likeness on HBO’s “Curb Your Enthusiasm,” the show he produces and stars in as Larry David’s friend and agent. The sixth season of the show will make its premiere September 9. “I also know my whitefish.”

We’re clearly talking food — throwback dishes for a Jewish improv comedian with roots in Chicago, south Florida, and New York — because it’s at the forefront of Mr. Garlin’s recent material, namely his first writing-directing effort, “I Want someone to Eat Cheese With,” which opens next Friday.

“For me, being here is like being an alcoholic in a bar,” he quips, before pushing his shake aside. “Time on my hands in a deli is dangerous. I’m a romantic about places like this and [the celebrated writer] Paddy Chayefsky, though.”

In the upper echelon of Hollywood’s comedy world, Mr. Garlin, 45, enjoys renown for his own mastery of a lost art: the pitch-perfect ear and prescient consultation for other comedians on what material will “kill.” A skillful stand-up and ensemble player, schooled at Chicago’s second City as well as on sitcoms such as “Mad About You,” he’s fluent in the routines of Jack Benny and Phil Silvers but also daringly contemporary, having provided counsel not just to Mr. David but to Jon Stewart and Denis Leary, among others. And though he loves his deli, Mr. Garlin, a stroke survivor who fights diabetes as well as other chronic health problems, eats healthy now. With a wife and two children, two unnamed television shows in development, and a new movie script making the rounds, it’s a good time for him, and even ice cream can’t compete with this confluence of successes.

In fact, “Cheese” isn’t about food. Not directly. A loose improv-style tribute to Chayefsky’s 1953 film “Marty,” the movie follows a down-on-his-luck Chicago comedian who lives with his mother, fails with women, and numbs his disappointment with Kozy Shack rice pudding — calories in place of sex. He’s not the first comedian to go there, but in his character’s casual encounters with friends and potential lovers — including Bonnie Hunt, a deliciously perverse Sarah Silverman, and a few “Curb” alumni — he evokes nostalgia for simple things: companionship, pudding, and not remaking such a classic film as “Marty” with a boy-band front man in the starring role.

He also touches on an oft-ignored topic: what it feels like as an overweight man to be rejected by the world. At one point in the film, Ms. Silverman’s character claims to just want to try sex with a big guy. It’s funny for its intrinsically dark realism; male body-image humor doesn’t often play on celluloid, and it’s never delivered with an optimistic joie de vivre.

In real life, though, Mr. Garlin is as graciously confident as his “Cheese” character is perplexed by the unfairness of life. “I don’t try to see myself a particular way or do anything specific with my material, he says. “I just do what I do. What’s natural. If people dig it, great.”

And people do. Even though “I Want someone To East Cheese With” lost financing during the two years it took to make, Mr. Garlin’s friends pitched in with cameos, and he finally found a distributor as well as a national home for the film on IFC on Demand — a practical place for the film to exist for a short while since so few Americans have access to the indie theaters that will screen a smaller movie.

“You know, you can go one way or the other, up or down, and I choose to go up,” he says. “I really don’t think about myself that much. I don’t analyze what it’s like to be me; I just am me.”

That inspires me to remind him of one memorable “Curb” episode in which Richard Lewis, playing himself, becomes enraged that someone has stolen his personal catchphrase: the “‘blank’ from hell.” In fact, Mr. Garlin has a trademark quote in real life — “a big bowl of ‘fill in the blank'” — but he’s at peace with sharing his intellectual property.

“The phrase is on my movie posters, actually — ‘sometimes love is Just a Big Bowl of Wrong,'” he says. “And HBO, well, they use it, but I’m not angry. They sell T-shirts that say, ‘A Big Bowl of Wrong.’ But that’s okay. It’s my contribution.”

In fact, “Curb” was Mr. Garlin’s idea for Mr. David, whom he befriended over the years on the comedy-club scene. “I had gone on tour with Denis Leary and Jon Stewart to help them develop their HBO specials, and while I was on the road with them, I conceived this idea of what would it be like to do an HBO special that’s about the making of an HBO special,” Mr. Garlin said. “We wouldn’t even have to do the actual special. so I approached Larry about it, and that’s what became the first ‘Curb’ mockumentary, which led to the series.”

In other words, don’t watch “Curb” and pigeonhole Mr. Garlin as a mere sidekick. Not only is he intricately involved in casting the improvisational reality-based show chronicling Mr. David’s fictional post-“Seinfeld”; he also shoulders responsibility for getting Mr. David’s viewpoint onto the screen, at all times, in every way.

“That’s actually my job,” he said. “Even when I’m acting and improvising, that’s my job. Even when I make up my own dialogue, that’s my job. I have to serve the scene. But it’s a joy. I’m lucky. I spend most of my time at work laughing.”

To my mind, I tell Mr. Garlin — and because he’s already called me a “nice Jewish boy,” I figure I’m allowed to broach the subject — there are two kinds of Jews: skinny ones and fat ones. Does he ever get jealous of the other type or get hired for gigs simply because of his size?

“I think it’s hurt my career,” he says. “The thin guy and the big guy on ‘Curb.’ Visually it works. But my comedy is so not about my weight that I could be 175 and still be the exact same comedian. If anything, the only thing weight does is hurt my health. It has nothing to do with how funny I am.”

Indeed, it’s clear that Mr. Garlin’s wit and intuition are what Hollywood relies on, and why he’s beloved in New York, a city nourished on Jewish humor. “I’d relocate to New York if I knew I could make enough money,” he says. “I’m a big city person, and debuting this film at the TriBeCa Film Festival last year was the best move I’ve made.”

Unsurprised — we both agree that anyone somewhat funny and semitic-seeming in comedy appears New Yorkerish — I tell him that I would not have believed that he grew up in Chicago if he wasn’t so nice. “Fuggetaboutit: New York’s like home,” he adds. “There’s a really famous dairy restaurant still on the Upper West side with fantastic rice pudding. You gotta try it.”