Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of weight management specialist NutriSystem (NASDAQ:NTRI) climbed as high as 10% today after its quarterly results and outlook topped Wall Street expectations.

So what: The stock has pulled back sharply since November on worrisome sales trends, but NutriSystem's Q1 results -- earnings per share of $0.01 versus a year-ago loss of $0.02 on a revenue increase of 11% -- coupled with upbeat full-year guidance are quickly easing those concerns. In fact, the company saw customer growth above 20% even as it increased prices during the quarter, suggesting that its competitive position and brand power are strengthening as well.

Now what: For the full year, management now sees EPS of $0.57-$0.67 on revenue of $392 million-$407 million, up from its prior outlook of $0.51-$0.61 on revenue of $385 million-$405 million. "Our channel expansion into retail and digital is enabling us to increase brand awareness and capture new customer segments," said President and CEO Dawn Zier. "We expect to achieve full year revenue growth in 2014 for the first time in seven years and are just beginning to realize our brand potential." With the stock now up about 115% from its 52-week lows and trading at a 20-plus forward P/E, however, I'd hold out for a much wider margin of safety before buying into that bullishness.