“I Feel Pretty” suffers from a fatal flaw: its premise. Built around the notion that there’s something inherently hilarious — even crazy — about a woman not supermodel-thin or -gorgeous behaving with the confidence of one who is, the comedy treats its star, Amy Schumer, as if she were Chris Farley in the “Saturday Night Live” skit “Chippendales Audition.”

In that classic sketch from 1990, the late actor — nearly 300 sloppy pounds of him — does a sexy striptease next to a nervous, insecure and very buff Patrick Swayze. It’s funny because Farley, without his shirt on, and his blubber set in motion to Loverboy’s “Working for the Weekend,” is kind of, well, ridiculous.

Schumer, although zaftig, is no Chris Farley.

She plays Renee, an ordinary woman who wakes up from a head injury with the self-esteem of Beyoncé. In one scene, her character dares to enter a boardwalk-bar bikini contest. It’s meant to produce gales of laughter but delivers mostly groans instead. In that set piece, Renee loses the contest but captures the heart of her beau, Ethan (Rory Scovel), with her verve. Inner beauty, the film seems to be saying, is more important than rock-hard abs.

Yet it encapsulates much of what is wrong with this comic misfire. “I Feel Pretty” tries to deliver a message of empowerment — that ordinary women needn’t struggle to meet unreasonable standards of beauty to feel good about themselves — but it ends up pushing its pernicious opposite: If you don’t look like Emily Ratajkowski, the film says, a rail-thin model and actor who has a small role in the film, you’re unworthy of attention and love. If the bikini scene is funny — and it’s not — it’s because no woman who looks like Amy Schumer ought to be that comfortable in her own body.

“I Feel Pretty” wants to have its cake and eat it too — to laugh at women because of how they look, while scolding us for doing so.

There are other problems as well. Co-written and co-directed by Abby Kohn and Marc Silverstein (the writers of “Never Been Kissed,” making their directorial debut), “I Feel Pretty” presumes that conventionally attractive women — or at least the vast majority of them in this film — are stuck-up jerks. When Renee asks a pretty woman on the street where she got her dress and learns that it’s from Target, Renee whispers, conspiratorially, “Aren’t girls like us so lucky that we can shop anywhere and still look fly as hell?” (The other woman rolls her eyes, as if to say, “What do you mean, ‘girls like us’?”)

That Target reference — along with scenes that namecheck SoulCycle and Zumba and a plot that centers on Renee’s employer, a high-end cosmetics company preparing to enter the mass-market makeup business — lend the film not verisimilitude, but a sickly veneer of consumerism and brand worship.

(Courtesy Mark Schäfer | STX Films) Amy Schumer, next to Rory Scovel, plays a woman who wakes up changed after a head injury.

Later, when Renee and Ethan are having sex and he catches her looking at herself in the mirror, he says — incongruously, given his own unpretentiousness — “That is so hot.” It’s a bit of a mixed message to suggest that superficial self-regard is both desirable and, later in the film, during Renee’s inevitable speechifying about inner beauty, deplorable.

But all of this would be moot if “I Feel Pretty” managed to be even remotely funny. Schumer, so incisive and so woke in early seasons of her Comedy Central series “Inside Amy Schumer,” which she created and which won multiple Emmys, seems to have gotten lazy. Beauty isn’t always effortless, it seems, but comedy is really, really hard.

★ (out of ★★★★)

I Feel Pretty

When • Opens Friday, April 20.

Where • Area theaters.

Rating • PG-13 for sexual material, some partial nudity and strong language.

Running time • 110 minutes.