New York ? From $2 dim sum to $150 foie-gras-and-truffle burgers, New York is a city that always eats – and often out.

But lately, the restaurant table has become a battleground.

New city rules require chain restaurants to display calorie counts on menus. A restaurant lobbying group sued in federal court in January to prevent the city from enforcing the requirement, which is due to take effect at the end of March.

Proponents of the calorie disclosure say the measure will help diners make informed choices. More than half of the city’s adult population is overweight, and the city’s number of diabetes cases has doubled over the last decade.

Opponents say that restaurants are willing to provide the information, but that it’s a costly one-size-fits-all regulation. Smaller chains that change their menus often will be hit especially hard, they say.

Though the regulations apply only to chains with at least 15 locations nationwide – about 10 percent of the city’s restaurants – the New York State Restaurant Association is concerned that the rules will be extended to every city restaurant.

“The camel puts his nose in the tent and the next thing you know, he’s in the tent,” said Executive Vice President Chuck Hunt.

Chain restaurants are the focus, health officials say, because they tend to offer high-calorie dishes and large portions. And chains’ standardization means the rules will be easier to enforce, they say. Similar legislation has been passed in Seattle and San Francisco and is pending in many cities and states.

McDonald’s, Burger King, Starbucks and other chains already provide nutritional information on posters, tray liners, food wrappers or the Internet – disclosing, for example, that a McDonald’s Deluxe Breakfast with a regular-size biscuit without margarine or syrup has 1,070 calories – about half the recommended daily intake for a typical adult.

But diners rarely see the information and generally underestimate how many calories they consume, said Marion Nestle, professor of nutrition and food studies at New York University.

“People don’t understand calories very well,” said Nestle. “They have no idea how many calories they are eating.”