The following are the main NAICS /SIC codes for this industry. They were obtained by searching the North American Industry Classification System (NAICS) search interface.
NAICS 722110 Full-Service Restaurants; SIC 5812
NAICS 722211 Limited-Service Restaurants; SIC 5812
Search the NAICS site for other food related shops, including ice cream and bakery items.
The links below will help you find other relevant codes you may want to identify. You can also find NAICS and SIC codes by looking at the industry information for a company in a database like Mergent Intellect.
One source you can use to apply NAICS codes is the Business Patterns database from the U.S. Census Bureau. This can help you determine what has been the trend in a particular industry from a National, County, Metro, and Zip Code perspective. Please note, however, that this will probably not include those establishments that are purely web-based.
You can also use NAICS and SIC codes to find Industry reports from First Research.