In the January's O magazine, Oprah Winfrey confesses that she now weighs 200 pounds and has "fallen off the wagon.

"I'm mad at myself," writes Winfrey, 54. "I'm embarrassed. I can't believe that after all these years, all the things I know how to do, I'm still talking about my weight. I look at my thinner self and think, 'How did I let this happen again?'"

Look back at Oprah Winfrey's weight ups and downs over the years.

In the article (obtained by The Associated Press), Winfrey, 54, says she has struggled with an out-of-balance thyroid and the condition made her develop "a fear of working out." She confessed that she's packed on 40 pounds since she weighed 160 pounds in 2006.

"Yes, you're adding correctly; that means the dreaded 2-0-0," Winfrey says. "I was so frustrated I started eating whatever I wanted - and that's never good."

See photos of stars who have packed on pounds for movie roles.

She says she hit rock bottom earlier this year when she wanted to skip an April 26 taping with Cher and Tina Turner in Las Vegas because she felt like "a fat cow.

"I wanted to disappear," says Winfrey, who has famously yo-yoed over the years (she once weighed as many as 237 pounds).

She goes on to say that her goal now isn't to be thin; she just wants to be healthy.

See Us Weekly's Weight Winners of the Year.

So she is launching the "Best Life Week," beginning Jan. 5 on her talk show. Winfrey's weight and height put her body mass index at 31.8, which is obese, according to the Centers for Disease Control and Prevention, The AP reports.

"I definitely wasn't setting an example," Winfrey writes in her article. "I was talking the talk, but I wasn't walking the walk. And that was very disappointing to me."

Get more Us! Follow us on Twitter, Friend us on Facebook, Subscribe to Us Weekly