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 specialty food distributor United Natural Foods (Nasdaq: UNFI) are looking healthy today as they jumped as much as 10.2% overnight on heavy volume.

So what: The just-reported second-quarter results and third-quarter outlook were all in line with analyst projections, except that sales in the quarter came in strong and new sales guidance is higher than the old one. The market is taking management's confidence as a good sign.

Now what: Here's the funny bit: United Natural's management pinned the good sales on "the sustained strength of the industry across all of our customer channels," yet the announcement failed to drag competitors SUPERVALU (NYSE: SVU) or Nutraceutical International (Nasdaq: NUTR) along for the joyride. The same holds true if you zoom out to a 52-week view, where United Natural has beaten its rivals hands-down. If Mr. Market isn't paying attention today, United Natural's report could signal a buying opportunity on its competitors.

Interested in more info on United Natural Foods? Add it to your watchlist.

Fool contributor Anders Bylund holds no position in any of the companies discussed here. Motley Fool Options has recommended buying calls on SUPERVALU. The Fool owns shares of SUPERVALU. 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 is investors writing for investors.