CHICAGO — Sales growth slowed for top restaurant chains in 2013, signaling a more challenging competitive environment. The 500 largest US restaurant chains posted a 3.5 percent increase in annual sales last year, dropping significantly from 4.9 percent in 2012, according to Technomic Inc., a Chicago-based market research firm.

“Although we have seen overall growth within the top 500, the pace has slowed since last year,” said Ron Paul, president of Technomic. “Competition for share of stomach is getting more and more challenging. But brands that have found a way to differentiate themselves are gaining market share.”

US system-wide sales at the 500 chains grew to an estimated $264 billion in 2013, up more than $8.8 billion from the prior year.

Top growth among limited-service restaurants came from Asian eateries, bakery-cafes and coffee shops. Panda Express led the segment with 10.7 percent sales growth, followed by Panera Bread at 11.8 percent and Starbucks at 10.6 percent. Comparably, McDonald’s, the largest US chain, saw a small bump of 0.7 percent.

Another sub-segment in limited-service showing above-average growth was chicken chains, which grew 5.1 percent in 2013, led by Chick-fil-A (9.3 percent), surpassing KFC in the category.

On the whole, the limited-service segment had a 3.9 percent increase in annual sales, while full-service restaurants registered 2.4 percent growth, which dipped slightly from 2.9 percent in 2012. With an increase in sales of 6.2 percent, the full-service steak category leads the full-service segment, driven by gains at Texas Roadhouse (11.1 percent) and LongHorn Steakhouse (12.8 percent). Buffalo Wild Wings drove growth among varied-menu chains with a 12.9 percent growth in sales.

More than two-thirds of the top 500 chains experienced at least nominal increases, while 156 chains had sales declines in 2013. Widely mixed results across segments and menu categories demonstrate overall competitiveness in the industry, Technomic said.

Internationally, the top 500 restaurant chains outperformed domestic growth during the year with a sales increase of 4.4 percent.