CHICAGO – Fast casual dining is drawing lots of attention as it continues to be the hottest segment of the restaurant industry, according to reports from the National Restaurant Association’s annual Restaurant, Hotel-Motel Show taking place in Chicago this week.

Even before the show’s official kick-off, a preconference day focused on the growing fast casual segment, giving restaurant executives a view of where the segment is headed and its opportunities.

“Although there are pockets of growth in the larger restaurant segments, fast casual continues to be a growth engine in terms of units, sales, and appeal,” said Darren Tristano, executive vice president of Chicago market research firm Technomic, in an article in QSR magazine.

The sector continued to steal share away from full-service restaurants last year and propelled limited-service restaurant growth, according to Technomic, rising to 15 percent of the $231 million limited-service sector. Fast-casual sales jumped 11 percent last year.

“We expect fast casual to continue to grow at a rate of about 9 –10 percent annual over the next five years,” said Tristano, who was one of the speakers at the Trends & Directions conference.

Even with this growth, fast casual is evolving: “The shift is more and more on the quality of the food and the quality of the service,” said Geoff Alexander, executive vice president and managing partner of Chicago-based Wow Bao, a six-unit division of Lettuce Entertain You Enterprises, during the Restaurant Show’s fast-casual executive panel.

QSR magazine writes that panelist Marc Simon, president and CEO of Rubio’s Restaurants, based in Carlsbad, California, added that customers also increasingly “want to know the provenance of their food.” That trend, along with the demand for sustainable products and responsible practices, “is here to stay,” he said, and is ingrained in the chain’s more than 190 restaurants.

The idea of knowing where the food originates also goes to the healthy halo that fast casuals have cultivated. “It’s a perception of healthy,” Alexander said. While the word low is important for older generations’ view of healthy food—low fat, low calorie, low sugar — Millennials “are all about sustainability and where the food comes from.”

And as the panelists all agreed, as fast-casual restaurants continue to grow, it’s essential to stay true to the brand’s culture.