Two years after the calorie content of menu items first started appearing on the menus of Seattle chain restaurants, just 1 in 4 customers who frequented those establishments said they used that nutritional information to guide their consumption choices, a new study finds.

In addition, roughly 4 in 10 customers acknowledged they didn’t even notice the new information.

But before you conclude that posting the caloric value of restaurant food is a virtually worthless exercise, consider this: In the months just before Seattle’s calorie-posting experiment began, only 8 percent of customers eating at chain outlets said they took the calorie content of their favorite foods into account when making their orders. And 18.6 percent reported that they even saw calorie counts on serving boards and menus.

That’s actually progress: over 2½ years, Seattle’s calorie-posting experiment tripled the percentage of people who saw useful new information on menus-from 18.6 percent in May 2008 to 59.4 percent in December 2010. In the same period, the proportion of consumers who let those calorie counts inform their ordering decisions also tripled-from 8.1 percent to 24.8 percent.

The new research, published Tuesday in the American Journal of Public Health, is not the first to suggest that calorie posting-now the law of the land-has failed to wean a nation of fast-food diners off their triple-bacon cheeseburgers or prompted a boycott of calorific coffee concoctions.

But it does offer the longest look available at this point in the evolution of Americans’ behavior when they are provided some key information about the food choices before them. While calorie posting is now required by federal law at most chain restaurants and eateries across the country, King County, Wash. — which encompasses the Seattle metropolitan area — was among the first local jurisdictions in the U.S. to require it.

Only New York City came before King County in adopting a regulation requiring most chain restaurants, coffee shops and snack bars to post the calorie contents of its menu offerings where ordering customers could see them. The King County Board of Health adopted the new regulations in March 2008, and they were broadly implemented on Jan. 1, 2009.

The new research found troubling disparities among King County diners’ responses to calorie posting. Compared with white, affluent and better educated residents, the study found that minority populations, people with low incomes and those with a high school education or less were not as likely to take posted calories into account when ordering.

Women and respondents who were married or “partnered” were also more likely to take posted calories into account when making their orders.