In 1988, Oprah Winfrey tugged a red wagon filled with fat across the stage of her television show to represent the 67 pounds she said she had lost on a liquid diet. Just a few years later she renounced dieting, but her fluctuating weight and the bias she has experienced because of it have remained frequent topics of discussion for both Ms. Winfrey and the media in the decades since.

Now, Ms. Winfrey, 69, has once again joined the discourse around diet, revealing on Wednesday that she had started taking a medication to manage her weight. Her announcement comes as demand has soared for new drugs like Ozempic, Wegovy and Zepbound that can help people lose weight, in part by suppressing appetite.

“The fact that there’s a medically approved prescription for managing weight and staying healthier, in my lifetime, feels like relief, like redemption, like a gift, and not something to hide behind and once again be ridiculed for,” she told People Magazine. Ms. Winfrey said she had decided to start taking a weight loss medicine after hosting a panel discussion, which she said had disabused her of the myth that weight hinges solely on a person’s self-control.

“I realized I’d been blaming myself all these years for being overweight, and I have a predisposition that no amount of willpower is going to control,” said Ms. Winfrey, who did not name the drug she was taking. A representative for Ms. Winfrey did not respond to a request for comment.

In the past year, Ozempic and drugs like it have upended conventional wisdom around willpower, weight and stigma. Perhaps no one more prominently embodies the cultural conversation around those issues than Ms. Winfrey.

“We can see Oprah as a crystallization of a broader struggle that many of us have with our bodies, going up and down in weight, when in reality our bodies are just comfortable at a higher weight than is deemed socially acceptable,” said Kate Manne, an associate professor of philosophy at Cornell University and author of an upcoming book on anti-fat bias.

That tension underscores just how complex it is to treat obesity, said Dr. Melanie Jay, the director of the N.Y.U. Langone Comprehensive Program on Obesity, who appeared on the recent panel alongside Ms. Winfrey.

“No one in the whole world has shown themselves to be more motivated to lose weight, to have the resources to do it, and yet very publicly has lost and gained weight and really struggled her entire life,” Dr. Jay said. “Which really goes to show how obesity is a disease that needs to be managed, and that the shame part of it is not helpful.”

Ms. Winfrey’s public proclamations about weight loss have mirrored national conversations about diet culture, the body-positivity movement that emerged in response and, now, society’s tentative embrace of weight loss medications, said Adrienne Bitar, a lecturer in American studies at Cornell University and the author of “Diet and the Disease of Civilization.”

“Her weight loss journey walks in lock step with all of America’s dieting experiences,” Dr. Bitar said.

Now, Ms. Winfrey has joined the many people turning to a new class of drugs used for weight management. As these medications have become more popular, the diet industry at large has pivoted toward them. Most notably, W.W. International, the company formerly known as Weight Watchers — which for decades proclaimed that strictly monitoring your diet could lead to weight loss — announced this spring that it had acquired Sequence, a telehealth platform that offers access to drugs like Ozempic. Ms. Winfrey has invested in the company and is a member of its board.

In making her announcement, Ms. Winfrey said that she was taking medication as a “maintenance tool.” People who begin taking such drugs typically lose weight for the first 18 months or so and then hit a plateau; if people stop taking a weight loss drug, they tend to regain pounds. She said that her doctor had prescribed the medication, and that it was part of a broader health regimen that included hiking and hydration.

Dr. Bitar suggested that Ms. Winfrey, a media expert, most likely made the announcement to shape her own narrative rather than leave room for further speculation about her weight-loss methods. Ms. Winfrey had previously not disclosed whether she had tried the medications.

Like many other female celebrities, Ms. Winfrey has been subjected to “crude, cruel coverage of her weight and health struggles” throughout her career, Dr. Bitar said. In a 1985 interview on “The Tonight Show,” Joan Rivers chastised her for gaining weight, telling Ms. Winfrey, “You shouldn’t let that happen to you; you’re very pretty.”

That criticism took an emotional toll, Ms. Winfrey told People. “It was public sport to make fun of me for 25 years.”

Even now, as experts say the evidence has never been clearer that weight loss is not as simple as “calories in, calories out,” some demonize the drugs as an easy way out. “There’s the sense that you would somehow be more virtuous for losing weight the old fashioned way, through white-knuckled willpower and diet and exercise and self-command,” Dr. Manne said.

Ms. Winfrey told People that she wrestled with the decision to take the drugs, but eventually came around. “I’m absolutely done with the shaming from other people and particularly myself,” she said.