Starting this week  (Sept. 16, 2012), McDonalds, the world’s No. 1 hamburger chain will start listing calorie information on drive-through and in-store menus.

The Oak Brook, Illinois-based retailer says it will be doing the posting of calories that their burgers and fries contains in a bid to help customers understand their food choices. The voluntary labeling of calories that McDonalds is undertaking has come from pressure from public health activists, as well as a new healthcare law that requires restaurants (especially those with 20 or more locations) in the U.S. to put calorie counts and other nutrition facts on menus. California and New York already have this requirement for restaurants.

The chain was previously strongly opposed to calorie disclosure suggestions but now it has changed position and says it views this as an opportunity. To make this work, the hamburger chain has been helping customers identify the ‘healthier’ choices on the menu by having a ‘Favorites under 400’ category, which are meals on its menu that have a calorie range below 400. It also changed its popular Happy Meal by cutting the fries portion and adding an apple. It has plans to include produce options in 2013 such as a McWrap that will have cucumber slices and a breakfast option, the Egg McMuffin with egg whites and whole grain muffins.

The retailer already provides calorie information in Australia, UK and South Korea, but this will be the first time it does so in the United States.

Panera Bread Company became the first restaurant to have voluntary calorie disclosures in 2010. Subway, best known for its sandwiches, has used calorie information disclosures to sell its products as healthier options to competitors like McDonalds and Burger King Worldwide Inc.