GRA has also recently signed a partnership with PepsiCo (ticker: PEP) and Sysco Corporation (ticker: SYY), both of whom approached GRA to consult with them to help make the businesses they own more sustainable.

Yet certified green restaurants make up only a very small percent of the restaurants in the U.S.. With 40 percent of restaurants surveyed by Fast Casual magazine using Styrofoam take out containers, they won't be green any time soon. Most restaurants haven't been part of a third party verification system and don't readily supply information on their environmental impact for consumers and stakeholders to verify what is a real commitment to the environment and what is just green hype.

Investors need to look first at the sustainability fundamentals: good disclosure, a trend of positive performance on issues of environment, labor relations, animal welfare, and product nutrition, and policies and programs that extend to operations of franchised locations and suppliers.

"Fast food companies that show CSR leadership are by no means perfect, but are more willing to engage stakeholders and report on how they have learned from mistakes," said Kennedy. "Some of the most clear-eyed critics of the industry are the long-time NGO advocates who have developed relationships with companies over years, or even decades. They often have a sense of which companies "you can work with" and which ones give the run around."

"It's reallyall about the results and measurable outcomes," said Annika Stensson, director of media relations for the National Restaurant Association. "The investors, of course, have to understand the issues to fully comprehend what efforts have an impact. For example, while not the sexiest of environmental issues, saving energy is one of the most impactful ways to go. By simply changing light bulbs, training staff to conserve energy, using energy-saving, an establishment can make a big difference."