Oprah says she's lost 26 pounds using Weight Watchers, and now the stock is surging

Oprah Winfrey says she's lost 26 pounds, thanks to Weight Watchers.

In a new ad for the company she tweeted on Tuesday afternoon, Oprah said she lost the weight despite eating bread every day.

She says, "I don't deny myself bread. I have bread every day. That's the genius of this program. I lost 26 pounds and I have eaten bread every single day."

Weight Watchers shares jumped by as much as 17% in trading on Tuesday.

Weight Watchers uses a points system to help members track the nutrition and calories in what they're eating. Everyone gets a daily allowance to increase their number of food choices without sabotaging a weight-loss plan.

Last October, Oprah bought a stake in Weight Watchers, joined the program, and became a member of its board. Shares rocketed more than 100% following the news that day, although they're down 29% over the past year.

Here's the move higher in the shares:

And here's the ad: