“These suits have a power to hold,” Lizzo, the Grammy-Award-winning singer and fashion entrepreneur, said in a video interview. “Let me tell you something: I have broken into a sweat trying to get some of these on.”

That Lizzo, a trailblazer of fat acceptance, has had to squeeze into bathing suits she developed for her brand Yitty was a striking confession. But she has tailored the concept of body positivity — that popular movement that urges self-love no matter your shape or size — to fit the times.

“The idea of body positivity, it’s moved away from the antiquated mainstream conception,” she said. “It’s evolved into body neutrality.”

Yet to hear her tell it, she is anything but neutral. “I’m not going to lie and say I love my body every day,” Lizzo, 35, said. “The bottom line is, the way you feel about your body changes every single day.”

She continued, “There are some days I adore my body, and others when I don’t feel completely positive.”

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A promotional campaign this year that teased Yitty swimwear, an extension of the line of bras, leggings and other shapewear Lizzo introduced two years ago, showed the singer flaunting her backside in a one-piece thong swimsuit. Models in the campaign similarly reveal generous amounts of flesh, wearing a series of one- and two-piece swimsuits.

“I’ve made my own wardrobe,” Lizzo said. “And now I get to be the C.E.O. and supermodel for my brand.”

Produced in partnership with Fabletics Inc., Yitty’s parent company, the swimwear is offered in sizes from 6X to XS. (The brand lists the largest sizes first.) It is aimed at the kinds of customers who may already own Yitty undergarments or similar items from Skims or Savage x Fenty — each of which, like Yitty, makes products using a stretchy combination of nylon and spandex.

What’s the difference between those products and Yitty swimwear? The bathing suits are made partly from recycled fabric, are meant to resist chlorine and are engineered, Lizzo stressed, “to create even more of a hold.”

The swim line includes a square-neck bikini top as well as bikini bottoms, shorts and one-pieces described in promotional copy as “cheeky,” “high-waist” and “waist-cinching.” Items are priced from about $50 to $100.

The range of available sizes, according to Lizzo, makes it easier to find something a little tighter (or looser). “If somebody wanted more or less compression, we give you the power to do that,” she said. “Just buy a different size. This line is about freedom.”

Lizzo, who is not touring at the moment, has lately had a bit more freedom herself to develop her line or to take up feel-good pursuits like exercise. “I’m taking the time every day to put some love into my body,” she said. “There is never a day when I regret taking a walk or doing some Pilates.”

She is dieting as well. “I’ve been methodical, losing weight very slowly,” Lizzo said. Others recognized for advocating candid self display have faced pushback after losing weight from people who see it at odds with self-love.

The singer, of course, is no stranger to controversy. She declined, through a publicist who was present for Lizzo’s video interview, to comment on ongoing lawsuits accusing her of harassment and of creating a hostile work environment, allegations she has repeatedly denied. Through her publicist, Lizzo also declined to comment on attacks on her appearance and character by Candace Owens, a conservative political commenter.