Many short sellers of Weight Watchers no doubt felt too down to look in the mirror this week after company stock unexpectedly ballooned nearly 170 percent.

You can thank (or blame) Oprah. The influential former talk show hostess bought a 10 percent stake in the weight management company, sending its shares up from $6.79 to $18.25 in as few as two trading sessions.

This is hardly the first time one of Oprah’s endorsements, whether verbal or monetary, has lifted a struggling business or product. There’s even a name for it: the Oprah Effect.

No matter your opinion of Oprah—her politics, her tastes—you have to admit that she’s a phenomenally savvy businesswoman, whose rags-to-riches success has helped make her one of the most powerful women in not just the U.S. but the world. As such, it’s important for investors to pay attention to her and other such “smart money” influencers. Their decisions often have the power to move markets.

So what’s moving gold right now?