Oprah Winfrey Was 'Blamed and Shamed' for Weight for 25 Years: 'Didn’t Occur to Me That I Could Feel Angry' (Exclusive)

Oprah Winfrey is reflecting on how it felt to be widely scrutinized about her weight for so many years.

The multihyphenate star, who turns 70 next month, says that she was often “blamed and shamed” for her body journey, especially when her eponymous hit talk show was on TV.

"It was a public sport to make fun of me for 25 years," Winfrey tells PEOPLE in this week’s cover story. “The things that were said about me, said to me, around me, the jokes that were made. You could not get away with it in the slightest sense today.”

A particularly hurtful moment, she says, came early in her career, when she ended up on acerbic fashion critic Mr. Blackwell's list.

"I was on the cover of some magazine and it said, 'Dumpy, Frumpy and Downright Lumpy,' " Winfrey recalls. 

“I just accepted that as that’s what it is, and I didn’t feel angry. I felt sad. I felt hurt. I felt shame. But it didn’t occur to me that I could even feel angry,” she says. “I swallowed the shame, and I accepted that it was my fault.”

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The turning point for Winfrey came in July during a taped panel conversation with weight loss experts and clinicians, called The State of Weight, part of Oprah Daily’s Life You Want series.

"I had the biggest aha along with many people in that audience," she recalls of the discussion, which was posted online in September. "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."

She adds, "Obesity is a disease. It’s not about willpower — it's about the brain."

Once she reconciled the science, Winfrey says she "released my own shame about it" and consulted her doctor, who went on to prescribe a weight-loss medication. "I now use it as I feel I need it, as a tool to manage not yo-yoing," she says, opting not to name the specific drug she takes.

"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. I’m absolutely done with the shaming from other people and particularly myself."

For more on Oprah Winfrey, pick up the latest issue of PEOPLE, on newsstands Friday.