Not long ago, grocery stores, supermarkets, even fast-food chains were stockpiling any product with a label that read "low-carb" or "Atkins-approved." But consumers soon grew skeptical of diet fads, and the low-carb craze vanished into thin air. (Has anyone seen a half-gallon of Ben & Jerry's Carb Karma ice cream lately?)

Where did all those impulse-driven consumers go? If a recent decision by Wal-Mart to enter the organics market is any indication, they've gone to the natural foods aisles. Already the No. 1 seller of groceries, Wal-Mart sent chills through the backbones of niche grocers like Whole Foods and Wild Oats by announcing its entry into the naturals space. The top retailer is doubling its organic food offerings this year and stepping up plans for organic baby clothes, infant formula, and T-shirts. Sam's Club already carries hot-selling yoga outfits made from organic cotton. In dog-days-of-summer terms, the Bentonville, Arkansas low-prices giant is about to do a cannonball into a $15 billion organics pool that could drain the water for the rest of the swimmers.

Wal-Mart's move into the lucrative organics market is seen as part of a broader greening strategy. In response to unrelenting flak from anti-globalization groups, unions, and the "small-is-good" crowd, the company has done an aggressive turnabout on its former environmental thinking. It's reported that Wal-Mart superstores are getting an energy-conservation makeover designed to cut electric usage by 30%, and the big-box retailer now donates millions to wildlife preserves around the U.S. The company even hosted a private showing of Al Gore's big-screen science-fiction thriller, "An Inconvenient Truth."

But does the greening of Wal-Mart make sense? Does the average Wal-Mart shopper care about organic food production? While many analysts are debating the matter, it is consumers who will answer such questions; they will decide if Wal-Mart's eco-conscious marketing represents substantial change or temporary opportunism. From a revenues perspective, Wal-Mart is likely to profit, even if its organics blitz lasts only as long as the now-defunct low-carb fad.