Weight Watchers (WW 5.52%) stock soared an amazing 287% in 2017, and shares have gained over 550% since television star, Oprah Winfrey, joined the company as a major shareholder and spokesperson in Oct. 2015.

In this segment from Industry Focus, we look at the "Oprah Effect" and consider how her presence has fueled both Weight Watcher's earnings growth and its shares.

A full transcript follows the video.

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This video was recorded on Jan. 9, 2018.

Vincent Shen: In the last week of 2017, we aired the first annual Industry Focus Awards -- definitely check out those episodes if you haven't heard them yet. From that award series, I successfully pitched and won the award for the most valuable player category thanks to my pitch for Weight Watchers and its brand ambassador and major shareholder, Oprah Winfrey.

Oprah and Weight Watchers launched their partnership in late 2015. She took a 10% stake in the company, she claimed a board seat, and has really gone on to become the face of Weight Watchers. Thanks to her fame and her influence with millions of consumers, you combine that with some of the broader strategic changes that the company has made, and Weight Watchers was one of the biggest gainers on the stock market in 2017, with shares pretty much quadrupling in value. Now, we're just over a week into 2018, and the bullish rally continues. Yesterday, the stock traded up over 12% thanks again to news regarding Oprah. Shares, I believe, are up another 4% to 5% before we got into the studio to start recording. So there's a lot of speculation here, admittedly. But what happened exactly, Asit?

Asit Sharma: A couple of things happened since the new year. On the 2nd of January, shares were up 8%, because Weight Watchers announced that it has enlisted DJ Khaled as a brand ambassador. He has over eight million Twitter followers, so this is like oxygen for Weight Watchers' stock. This follows the model that Oprah developed, in which she tweets out her progress to her following, and subscribers jump, the stock jumps. It's by design an extremely effective way for Weight Watchers to combat its formerly stodgy image, and also repel the attacks that have come from a plethora of free apps that you can access now from your smartphone to your smartwatch to get into shape. What's been happening is, the confluence of influencers is really going to propel the stock further. Maybe we'll have to talk about the valuation. But these were the main events so far this year.

Shen: On the Oprah front, I think it's really tough to quantify but also separate the influence she's had on the strong results the company has enjoyed the past two years. A lot of people were talking about, for example, her acceptance speech, I think it was two nights ago now, at the Golden Globes. A lot of people were reading into this as hinting at a potential presidential run. I think that's behind a lot of the activity in the stock the past few days. And I've read through that transcript, and there's nothing in there that points directly to her starting a presidential run. But the fact that she offered up arguably the most notable moment of the night at that awards ceremony, and some other stories and hints that she might run in 2020, that's all positive PR for her, and then, by association, Weight Watchers, because of the partnership, it helps explain the 17% gain the stock has enjoyed so far just this week.

If we take a snapshot of the financial results, I always think it's interesting, you go back to the third quarter of 2015, call this the pre-Oprah period, revenue was at $273 million for that quarter, it was down 21% year-over-year. Then, you jump forward two years to the third quarter of 2017, the partnership is in full swing, revenue is at $324 million, up 15% year-over-year. Earnings per share are up over 70% over that two-year period. Active subscribers are up over 30%. Customers are sticking with Weight Watchers services for much longer.

So sometimes, I'm tempted to give my usual warning and caution regarding market noise, and how Foolish long-term investors should stay focused on the company's fundamentals, but I think it's tough to deny how unique the situation is. Asit, you mentioned influencers. Oprah is not on the core management team at Weight Watchers. She's not a chief executive of any kind. But the strength of her personal brand, and this new partnership with DJ Khaled, that has all undoubtedly contributed to the company's turnaround, strong results, and I think it's going to continue to play a pretty important part in Weight Watchers' future.

I was chatting with other Fools before coming into the studio about this. Do you know of any other examples of companies that have really benefited so handsomely from having the right spokesperson or brand ambassador? The only one I can really think of was Nike and Michael Jordan.

Sharma: Yes. And Oprah brings something a little different than Michael did. Michael brought us a sense of being like Mike. We wanted to replicate his success by wearing his shoes. But you have to go, in my opinion, all the way back to Joe DiMaggio and his endorsement of coffee products, to find such an influential brand ambassador. What Oprah has, it's slightly different than other influencers out there, it's credibility and trust. People really trust what she says. In fact, financial institutions see her as extremely credible. The stock popped when she announced her investment, and stepping up to endorse the brand, simply because Wall Street understands, she's always been a shrewd businesswoman, and she wouldn't have taken this gig had she not seen the potential.

So it wasn't just about marrying up a celebrity with a brand. Oprah has a track record of building successful businesses. She has a platform that crosses several types of media, and a huge following of people who really believe her and see her as credible in almost any endeavor she undertakes. And it really is hard to think of someone who has so much influence on this level of trust and credibility. Again, we can go back to products and talk about people like Steph Curry and Michael Jordan. That's a different type of product endorsement. I think this is unique. And I'm with you, I think she's actually impacting Weight Watchers in a good way, that she's lifting the subscriptions, she's lifting their paid revenue. And that's something an investor can put money behind. So I doubt the stock will replicate last year's success. You probably know this better than I do, Vince, but what, 250% just last year?

Shen: It was even more than that. I mentioned on the awards show, one of the biggest gainers on the market, hands-down. It blew the other Industry Focus cast members away, and I think it was what was able to get me that MVP win.

Sharma: Congratulations, by the way!

Shen: It was a great pitch, and honestly, the story for 2017 for this company so far is really incredible to follow.