NEW YORK -- Weight Watchers is getting another boost from Oprah Winfrey.

The weight-loss company's shares are soaring as a TV commercial starring Winfrey begins to air.

The commercial shows past videos of Winfrey working out and referencing her struggle with weight, a frequent topic of Winfrey's former talk show. The ad ends with Winfrey asking viewers whether they're ready to join her.

"Let's do this together," she says.

She tweeted the ad to her more than 30 million followers 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 also has made changes to its plans to fit in better 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 $3.96, or 20 percent, to $23.33 in afternoon trading Wednesday.

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 still is down about 7 percent from a year ago.

Winfrey is on the new plan and she said in an October appearance on "The Ellen DeGeneres Show" 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 now is worth more than $148 million.