Oprah Winfrey has stepped down from the WeightWatchers board after nearly a decade to prevent any conflict of interest.

Winfrey discussed her decision publicly just before the broadcast of an "Oprah Special: Shame, Blame, and the Weight Loss Revolution," set to air on Friday.

"I decided [to leave the Weight Watchers board because this special was really important to me, and I want to be able to speak with whatever voice I want to give voice to," Winfrey said. "And Weight Watchers has now become a people's health and wellness company that also prescribes drug medications for health and wellbeing."I did not want to have the appearance of any conflict of interest."

She further made it clear that she had given all her shares to the National Museum of African American History so that no money was incurred from the special.

Winfrey said she made the decision after her high-profile admission last year that she had taken, and later abandoned, medication to help her lose weight. In a Dec. 14 interview with People, she said, "I realized I was blaming myself all these years for being overweight, and I have a predisposition that no amount of willpower is going to control. Obesity is a disease. It's not about willpower; it's about the brain."

In her lifetime profession, the 70-year-old media mogul has consistently opened her mind to reporters about her weight struggles. Now, after various controversies, Winfrey wants to raise the conference to talk about the recognition of obesity as a chronic condition, calling for health equity.

"An Oprah Special: Shame, Blame, and the Weight Watchers' Black Revolution" premieres Monday, March 18, on ABC and starts streaming the following day on Hulu.