Image source: Weight Watchers.   

One of the trickiest things about dieting is managing the ups and downs of weight loss. It seems as if Weight Watchers (NASDAQ:WTW) shareholders are going through the same thing. The stock soared 30% after a Securities and Exchange Commission filing revealed how powerful having Oprah Winfrey as a spokesperson and stakeholder can be for the provider of weight management solutions.

The regulatory 10-K filing claimed that Winfrey talking up Weight Watchers provided it with more than 1 billion earned media impressions. That's a lot of "free" advertising, and as soon as Bloomberg picked up on that morsel, other financial outlets began to publicize the meaty milestone. 

However, is that really a surprise? We've known about "the Oprah effect" for years. If the media tycoon recommended something on her afternoon talk show or other subsequent media outlets, it would have a strong favorable impact on sales of that product or service. Tie in Winfrey's well-publicized ups and downs with her own dieting challenges and it was a no-brainer that Weight Watchers would benefit greatly from her endorsement. In short, it was a pretty weak catalyst that contributed to shares of Weight Watchers appreciating by nearly a third of its value.

Another thing that isn't a surprise is Weight Watchers stock moving. It's been one of the most volatile stocks since Winfrey disclosed shelling out $43.2 million for a 10% stake and a seat on Weight Watchers' board of directors. She ultimately increased her position to 15%. The stock rarely stands still these days. Let's look at that weekly gains and hits that Weight Watchers has experienced in recent months.

Week StartingCloseChange
12/7/15 $24.39 (7%)
12/14/15 $20.99 (14%)
12/21/15 $18.00 (14%)
12/28/15 $22.80 27%
1/4/16 $14.85 (35%)
1/11/16 $13.76 (7%)
1/18/16 $11.54 (16%)
1/25/16 $12.69 11%
2/1/16 $11.10 (13%)
2/8/16 $11.05 (0%)
2/16/16 $14.92 35%
2/22/16 $11.01

(26%)

2/29/16 $14.27

30%

Take in those nerve-rattling ups and downs. Weight Watchers has experienced double-digit percentage moves in 10 of the past 13 weeks. Outside of one flattish week in early February, we're talking about a move of at least 7% every single week since early December. Perhaps even more problematic for investors hoping that last week's pop will carry over into the new week, the stock's three previous double-digit percentage upticks were followed by declines of 35%, 13%, and 26%, respectively. You actually have to go back to late November to find the last time the stock has posted back-to-back weeks of gains.

Weight Watchers stock has become ridiculously volatile. Its one-year beta is clocking in at a sky-high 3.21, according to S&P Global Market Intelligence data. Most of these weekly moves have happened without a material news event driving the stock one way or the other. Sometimes there will be developments including a weak holiday quarter or a favorable journal study triggering the move, but the stock seems to always be on the move -- even in the absence of game-changing news. The stock should continue to be on a yo-yo, and we may have to wait until Weight Watchers lives up to "the Oprah effect" hike by posting membership growth for a quarter before we get a sustainable rally.