Shares of Weight Watchers International (WTW) jumped as much as 20 percent after Oprah Winfrey said she shed 26 pounds using the program, while eating bread every day.

In a video posted to Twitter, Winfrey, an investor and spokesperson for the company, declared her fondness for bread, saying she consumed it each day while losing weight.

Shares rose as high as $13.54 after the release of the video, following a pattern that also had shares of Weight Watchers rising after the media mogul said on "The Ellen DeGeneres Show" that he had lost 15 pounds.

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Shares finished up $2.17, or nearly 20 percent, at $13.29.

Winfrey in October announced she had purchased a 10 percent stake in the company, which has seen its membership decline in the face of competition from free fitness apps.