Weight Watchers stock is surging -- and so is the value of Oprah Winfrey's considerable stake -- after the company reported a boost in membership.
Weight Watchers International (WTW) shares climbed 14% on Wednesday. And the stock has quadrupled since Winfrey bought a big stake and joined the board of directors in 2015.
Winfrey holds about 10% of the shares. Her stake was worth $43 million when she bought it in 2015. It's now worth $154 million. And she has the option to increase her stake to 15%.
After the market closed Tuesday, the company announced that membership jumped 16% in the first three months of the year, to 3.6 million.
This is a critical period because it includes New Year's resolutions to lose weight. It immediately followed Winfrey's ad campaign in December, in which she touted her 40-pound weight loss.
Related: Weight Watchers is finally getting a new CEO
The company also reported gains in sales and profit, compared with the same period last year, when Weight Watchers lost money. It also raised its outlook for the year.
Weight Watchers announced last week that it's hiring a new CEO. Mindy Grossman, CEO of the Home Shopping Network. She'll take the top job in July, filling a position that's been vacant since September, when former chief executive James Chambers resigned.
--Paul R. La Monica of CNNMoney contributed to this report.
