Full-year profit may increase to as much as $3.50 a share, exceeding some analysts' estimates, as consumers grappling with higher food and gasoline costs spend more on lower-priced medicine and groceries, Wal-Mart said today.

Sales at stores open at least a year climbed 4.5 percent in the quarter, the most since 2004, spurred by tax-rebate checks and the retailer's lowered prices on cereal and shampoo.

"When consumers have to tighten their spending, they trade down," Jason Pride, research director at Haverford Trust Co., told Bloomberg Television. "In order to trade down, they have to shop more at a Wal-Mart."

Despite a tough U.S. economy, McDonald's Corp. posted an 8 percent gain in July same-store sales on Friday as hungry consumers worldwide lined up for breakfast items and the classic Big Mac sandwich.

Many consumers have cut back on eating out amid economic weakness and rising gasoline prices, but business at the Golden Arches held up well in July, especially in the U.S. International sales have typically been strong for McDonald's – a trend that continued in July. Same-store sales jumped 7.6 percent in Europe, led by sales in Britain, France and Russia. And in the Asia-Pacific, Middle East and Africa region, same-store sales climbed 7.2 percent because of extended hours and menu items.