Whole Foods is getting ready to launch its first national marketing campaign and expand home delivery as it looks to fend off bigger players muscling into the organic and natural foods category.

The company, based in Austin, Texas, said the marketing campaign this fall will explain to customers what makes it different and why it's better than other supermarkets.

"We believe there are real and substantive differences in the company and in the values and the foods that we sell," said Walter Robb, co-CEO of Whole Foods, during a conference call with investors.

In addition, he said the company is partnering with third parties to offer home delivery in 12 to 15 major markets, with plans for a wider rollout over time. Whole Foods declined to give details about which cities will get home delivery, but the company already offers delivery in select major markets, including New York City. And other major players such as Wal-Mart are testing delivery as well.

In coming weeks, Whole Foods also said it will test a new loyalty program, with plans to roll it out widely in time for the winter holidays next year.

The efforts come as Whole Foods struggles to spark slowing sales growth, which has worried investors that the company is losing ground in the organic and natural foods segment it once dominated. On Wednesday, Whole Foods sales at established locations rose 3.9 percent in its latest quarter, helped by a shift of the timing of Easter.

A year ago, the figure had climbed 7.5 percent.

The problem is that Whole Foods is contending with traditional retailers such as Wal-Mart Stores and Kroger Co. and even drugstores, which have significantly expanded their organic and natural food offerings.

To appeal to a wider range of customers, the company is trying to change its pricey image. The effort to keep prices down has included pushing its store brands, which are generally cheaper to stock than name brands.