The study evaluated the effects of new requirements for chain restaurants to label their menu items with their corresponding calorie content by following restaurant patrons 18 months after implementation of the law-a longer period than previously published studies.
The researchers looked at various types of chain restaurants, including burger restaurants, sandwich shops and coffee shops.
"Most people have no idea how many calories are found in restaurant meals," said lead study author James Krieger, M.D., M.P.H., of the public health department of Seattle and King County in Washington.
The study found that after the regulations were put in place, more people reported being aware of posted calorie information. After 18 months, customers of taco restaurants consumed fewer overall calories and customers of coffee establishments consumed fewer calories from beverages.
Those results may be due to "customization," Krieger said-people can decide whether to put additional calories of sour cream or guacamole on a taco, for example. In coffee houses, customers choose the size and the additives for a drink.
"There was not much change seen among burger and sandwich restaurant patrons. Women purchased fewer calories than men as a result of menu labeling, particularly at coffee establishments," he said.
"The point here is that change takes time, but that small changes all add up," said Tracy Fox, M.P.H, R.D. of Food, Nutrition and Policy Consultants in Washington, D.C.
Menu labeling is but one piece of the complex obesity pie, said Krieger.
"It's not the single intervention, but one of several intersecting, overlapping strategies that encourage us to eat healthier foods and be physically active," he added.
The finding was published in the American Journal of Preventive Medicine.