What happened

Weight Watchers International, Inc. (NASDAQ:WTW) stock was up as much as 13% during the trading day today, seemingly over early excitement about the earnings release planned for this evening, after the market closes.

So what

Weight Watchers is planning to release its Q4 and full-year 2016 earnings this evening, following the close of the market, but rival Nutrisystem (NASDAQ:NTRI) just released its own earnings that handily beat expectations, with sales up 21% year over year for the fourth quarter. The market seems to believe that Nutrisystem's success could be indicative of a rise in the number of interested dieters market-wide, which would mean a coming expectation beat for Weight Watchers as well.

A smiling woman speaking to a group of Weight Watchers meeting participants in front of a sign that reads "I'm not here to be average, I'm here to be awesome."

Image source: Weight Watchers International, Inc.

Now what

Weight Watchers stock has had a good last few months -- up 32% in the last six months. Some of the reasons for the stock's rise lately include news of celebrity and Weight Watchers major investor Oprah taking a more active role in the brand's marketing efforts, as well as the January announcement that the overhauled Weight Watchers weight-loss program won multiple first-place awards in U.S. News & World Report's Best Diets of 2017. 

Will Weight Watchers' stock continue its outperformance trend this year? There are a few reasons to be careful about this stock now, including its past volatility (the stock is down 82% over the past five years), as well as a surge in cheaper or completely free programs and health mobile apps that could cut into Weight Watchers' potential consumer base. Still, the company has clearly made some impressive moves in the last few months, and the stock could be cheap now -- trading at just 12 times forward earnings estimates -- if its success with its new programs continues in 2017.