Whether they want to or not, consumers will soon know how many calories they are eating when ordering off the menu at chain restaurants, picking up prepared foods at supermarkets, and even eating a tub of popcorn at the movie theater. The Food and Drug Administration is announcing long-delayed calorie-labeling rules on Tuesday, requiring establishments that sell prepared foods and have 20 or more locations to post the calorie content of food “clearly and conspicuously” on their menus. Companies will have until November 2015 to comply. The regulations will also apply to convenience stores, bakeries, coffee shops, amusement parks, and vending machines. FDA Commissioner Margaret Hamburg said the effort is just one way Americans can combat obesity.