With a low-carb wave sweeping the nation, how did Papa John's (NASDAQ:PZZA) post a 4% spike in comparable-store sales last month? Was it the pizza-fed Super Bowl crowd hitting up Papa for halftime deliveries? Nope. Sunday's big game took place in February. Papa John's results are even more impressive given that last year's Super Bowl did take place in January.

So, just how committed are we to the Atkins mandate to trim our dough intake? Good question. Certainly, at a time when chains like Donato's are testing low-carb crusts, it doesn't seem right for Papa John's to be doing this well sticking to basics. Then again, Tom Gardner has had Papa John's on his Motley Fool Hidden Gems Watch List for months.

And we're talking January here! What happened to all of those New Year's resolutions to cut down on fatty foods in 2004? Even Pizza Hut from the Yum! Brands (NYSE:YUM) family of fast-food concepts posted January same-store sales growth of 2%.

Operators like Darden (NYSE:DRI), Brinker (NYSE:EAT), and Outback (NYSE:OSI) all run chains that specialize in tossing pasta. Yes, they feel vulnerable. The latest print ads from Brinker's Romano's Macaroni Grill emphasize its grilled meat dishes. Talk about putting your grill before your macaroni!

At least burger chains like McDonald's (NYSE:MCD) and Wendy's (NYSE:WEN) can rely on premium salads, or follow Burger King into the realm of bunless burgers. Pizza shops have a much taller task if the art is reinvention.

That's why watching comps matters. It's a great early gauge for everything from trend vulnerability to the impact of pricing wars. So far in 2004, Papa John's is making a square living by providing round meals. Investors looking to bail might want to hold off on penning their Dear Papa John's letters. With nearly 3,000 locations worldwide, and all but 570 of those being franchised units, Papa John's has been a fast grower. More importantly, reports of the industry's demise seem to be greatly exaggerated.

Will trimming back on your carbohydrates intake really help you trim back that waistline? How does one start to stop? What is the ideal diet? All this and more -- in the Low Carb Way of Life discussion board. Only on Fool.com.