Weight Watchers stock soars as Oprah ad begins to air

The weight loss company's shares soared Wednesday as a TV commercial starring Winfrey began to air.

The commercial shows past videos of Winfrey working out and referencing her struggle with weight, a frequent topic of her former talk show. The ad ends with Winfrey asking viewers if they're ready to join her. "Let's do this together," she says.

She tweeted the ad to her more than 30 million followers on Tuesday.

Weight Watchers stock has more than tripled since October, when Winfrey bought a 10 percent stake in the New York company. Besides the new ads, Weight Watchers has also made changes to its plans to better fit in with Winfrey's message of living a healthy and happier life, and not just focusing on weight loss.

Shares of Weight Watchers International Inc. jumped $3.68, or 19 percent, to close Wednesday at $23.05.

Weight Watchers brought in Winfrey at a precarious time for the company. It has been hurt by the popularity of fitness trackers and free food-tracking apps. Despite recent gains in the stock, it is still down about 8 percent from a year ago.

Winfrey is on the new plan and she said in an October appearance on "The Ellen DeGeneres Show" that she lost 15 pounds in a few months.

While she slims down, her wallet is getting fatter. Back in October, Winfrey paid about $43.2 million for her 10 percent stake in Weight Watchers. That stake is now worth more than $148 million.