Healthy fast food? Americans are eating it up

Fast food doesn't have the healthiest reputation, but a new generation of restaurants is trying to change that.

Lyfe Kitchen is part of a growing trend in the industry called "healthy fast casual" restaurants, which offer health-conscious food for people on the go. The menu features organic fish tacos, baked chicken, even pizza -- but every meal weighs in at under 600 calories. No supersizing here.

"I think it's great because if I walk into a restaurant I'm always going to choose a burger and fries, so this kind of keeps me on the straight and narrow, coming to a place like this," said customer Lisa Curesky.

Lyfe Kitchen co-founder Michael Donahue spent 20 years learning the ins and outs of the fast food business while working for McDonald's. He saw a demand for healthier options and developed his chain for consumers who are more conscious about what they eat -- and what they want to avoid.

"We have no preservatives, everything is natural, baked, made to order, no fryers," he told CBS News.

Another leader in the healthy fast food sector is California-based Tender Greens, a chain with 17 locations and plans to open 13 more by next year.

Tender Greens turns to local farmers for its fresh vegetables and free-range chickens, feeding Americans' growing appetite for healthy, high-quality fast food options. "People have become more sophisticated around food, because of the farmers markets, because of innovative chefs," said owner Erik Oberholtzer.

Customers are willing to pay about $8 to $12 at such chains for a quick meal they feel good about, helping spur huge growth in the industry. "Healthy fast casual" restaurant sales totaled $384 million in 2014, up 30 percent from the year before.