Weight Watchers shares jump on Oprah ad

Oprah Winfrey bought a 10% stake in Weight Watchers in October for $43.2m

Shares of weight loss company Weight Watchers jumped nearly 19% on Wednesday after a television ad featuring Oprah Winfrey was shown in the US.

In an emotional one-minute commercial, the former talk show host spoke about her renowned weight loss struggles, flashing back to videos of her working out over the years.

She asked viewers to join her, saying "let's do this together".

Ms Winfrey bought a 10% stake in the company for $43.2m (£28m) in October.

New York listed shares of the dieting company have more than tripled in value since she bought a stake in one of the world's leading weight loss brands.

Her stake is now worth more than $148m.

The company, however, has been facing stiff competition from the popularity of fitness trackers and other free mobile apps which track your eating.

Despite the jump in shares since Ms Winfrey's involvement, the company's stock market value is still down about 8% from a year ago.

Earlier this year, Weight Watchers' founder, Jean Nidetch, who is credited with turning worrying about one's weight into a million-dollar industry, died at age 91.

Star power

Ms Winfrey, meanwhile, also tweeted the new ad to her more than 30 million Twitter followers on Tuesday, writing "Why I joined Weight Watchers".

During an appearance on "The Ellen DeGeneres Show" in October, the 61-year-old had announced that she was on a new Weight Watchers plan and had lost 15 pounds in a few months.

The company has also announced changes to its weight loss plans to fit in with the US billionaire's message of healthy and happy living.

In the TV commercial, Ms Winfrey says "Inside every overweight woman, is a woman she knows she can be".