WASHINGTON — Diners will have to wait until the end of 2016 to find calorie labels on all chain restaurant menus.

The Food and Drug Administration said Thursday that restaurants and other establishments will now have until December 1, 2016, to comply with federal menu labeling rules — one year beyond the original deadline.

The FDA said it is extending the deadline after restaurants and other retailers said they needed more time to put the rules in place. The agency said those businesses are in the process of training workers, installing menus and menu boards and developing software and technology for more efficient and specific label displays.

The rules will require restaurants and other establishments that sell prepared foods and have 20 or more locations to post the calorie content of food “clearly and conspicuously” on their menus, menu boards and displays. That includes prepared foods at grocery and convenience stores and in movie theaters, bakeries, coffee shops, pizza delivery stores and amusement parks.

The menus and displays will tell diners that a 2,000-calorie diet is used as the basis for daily nutrition, noting that individual calorie needs may vary. Additional nutritional information beyond calories, including sodium, fat and sugar must be available upon request.

The Obama administration has said menu labeling is just one way to combat obesity, since Americans eat and drink about one-third of their calories away from home.

Some of the rules are complicated. In grocery stores, for example, the labeling rules exclude prepared foods that are typically intended for more than one person.