Health inspectors can slap fines of up to $2,000 on fast-food and casual-dining chains if calorie counts are not displayed on their menus in the same font and format as the name or price of food items.
The move follows the city's 2003 ban on public smoking and a ban on artery-clogging trans fats.
New Yorkers appeared unfazed by the rule, and some said they would not be dissuaded from ordering a 540-calorie Big Mac at McDonald's or a 440-calorie Iced lemon Loaf at Starbucks.
The rule affects such restaurants as McDonald's; Burger King; Applebee's, operated by DineEquity Inc; Dunkin Donuts; Starbucks and Subway.
Don't go to McDonalds for a healthy lunch
"I'd be shocked if consumers weren't already aware that when they're eating in a fast-food restaurant, the cheeseburgers and fries and fountain drinks, are not healthy," said Morningstar analyst John Owens.
"People don't go to McDonald's for a healthy lunch. They go for a fast-food burger and fries," he said.
A city study last year found 30 percent of New Yorkers were consuming more than 1,000 calories at lunchtime.
Officials say the rule could prevent at least 150,000 New Yorkers from becoming obese and prevent at least 30,000 from developing diabetes over the next five years.
Is it time for South Africa’s big fast food chains to follow this example?