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 natural food grocer Whole Foods (Nasdaq: WFMI) jumped more than 14% in intraday trading as investors reacted to the company's fiscal fourth-quarter earnings report.

So what: Beating earnings estimates and raising guidance is a recipe for investor jubilation the same way a Philadelphia Eagles loss at home to the New York Giants is a recipe for fisticuffs. Whole Foods' fourth quarter was a touchdown with the two-point conversion, though, as sales advanced 15%, comparable-store sales increased 8.7%, and earnings per share rose 63%. Earnings per share of $0.33 easily outran the $0.28 that Wall Street had in its playbook, while the new guidance for 2011 earnings -- with a midpoint at $1.69 per share -- hurdled the previous estimates by both the company and analysts.

Now what: Whole Foods today looks cheap compared with Whole Foods of a few years ago, but you've got to believe in very robust growth to digest the valuation premium that the stock gets over traditional grocers like Kroger (NYSE: KR) and Safeway (NYSE: SWY). That said, management sounds pretty confident about growth -- both from continued growth in current locations and the opportunity to open new locations.

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Fool contributor Matt Koppenheffer does not own shares of any of the companies mentioned. You can check out what Matt is keeping an eye on by visiting his Motley Fool CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or on his RSS feed. The Fool's disclosure policy assures you no Wookiees were harmed in the making of this article.