WASHINGTON — Wondering how many calories are in that hamburger? Chain restaurants still don’t have to tell you, despite a 6-year-old law requiring calorie labels on menus.

Passed as part of the health care overhaul in 2010, the rules will eventually 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.

This month, the Food and Drug Administration said it will delay the rules — again — until 2017.

The years of delays have come as supermarkets, convenience stores and other retailers that are covered by the rules but never wanted to be part of the law have fiercely lobbied against them. The move will leave the final step to a new president, despite the Obama administration’s staunch support of menu labeling and other food policy to help Americans eat more healthfully. And it will give opponents more time to gather support for legislation that would roll back some of the requirements.

Restaurants and other retailers originally had until the end of 2015 to comply. Last summer, the FDA pushed that deadline back to the end of 2016. This month, they pushed the deadline back again.