Longtime believers in Weight Watchers (NYSE:WTW) stock received a nice payoff last month when shares soared more than 150% over a five-day period. The move came on the heels of news that Oprah Winfrey had obtained a 10% stake in the business. The celebrity will also be using her Midas touch as a brand ambassador for the weight management company.

Shareholders hope Oprah's influence can help revive the brand, which has suffered recently as more consumers look to the convenience of mobile weight loss apps versus more traditional weight management services such as those offered by Weight Watchers.

Let's take a closer look at what this means for Weight Watchers' stock, and whether there is still time for investors to get in on the action.

Go big or go home
Oprah, who has publicly struggled with weight loss in the past, is a perfect fit for Weight Watchers. Her celebrity endorsement should help the company attract loads of new customers. The public figure and former talk show host, after all, boasts more than 10 million followers on Facebook and nearly 30 million loyal fans on Twitter. Not to mention, the majority of these followers are women -- an ideal target market for Weight Watchers' products and services.

"Weight Watchers has given me the tools to begin to make the lasting shift that I and so many of us who are struggling with weight have longed for. I believe in the program so much I decided to invest in the company and partner in its evolution," Oprah said.

News of her involvement helped pushed the stock up more than 296% in the past quarter, to where shares currently trade at around $15 apiece. Yet, if you weren't one of the lucky ones to own the stock pre-surge, don't worry. We could see another rally in Weight Watchers stock in the months ahead. Let me explain.

The short end of the stock
Given the recent rally in shares of Weight Watchers, short-sellers are making big bets against the weight loss giant. More than 31% of Weight Watchers' outstanding shares are now sold short. This could lead to a short-squeeze in the stock if the company is able to over deliver on expectations in the quarters ahead.

Investors often place short bets on a stock when they believe it is overvalued or expensive from a valuation standpoint. And while it's true that Weight Watchers' stock price has skyrocketed recently, the stock is still trading 46% below its 52-week high. 

Oprah And Weight Watchers

Oprah Winfrey. Image source: Weight Watchers International.

It's a risky play for short-sellers with the New Year just around the corner. Weight loss is typically the No. 1 New Year's resolution among Americans each year. This means the post-holiday season is often the best time of year when it comes to member acquisitions for Weight Watchers. Additionally, the company recently raised its full-year guidance; Weight Watchers now expects fiscal 2015 earnings in the range of $0.57 and $0.72 per share, up from its prior guidance of between $0.40 and $0.70 per share. 

Investors will get more color on Weight Watchers business when it reports fiscal third-quarter earnings later this week. While it isn't likely that Weight Watchers will over-deliver in this quarter, Wall Street's expectations are exceedingly low. The Street, for example, predicts a 22% decline in sales growth year over year. Meanwhile, analysts expect earnings per share of just $0.20, down from $0.68 per share in the year-ago period. 

These low expectations, coupled with high short interest in the stock, could trigger a short-squeeze and thus send shares higher if Weight Watchers is able to deliver better-than-expected results. With Oprah now set to play a hands-on role in the transformation of the company, Weight Watchers' future could be a bright one. Therefore, long-term investors may still be able to reap the rewards of this multi-year turnaround story.

Tamara Rutter has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.