November 17/New York/Huffington Post -- The point of calorie counts on fast food restaurant menus is to spur customers to eat more healthfully, but a new study suggests they might not really work.

Not only do fewer than half of patrons, on average, notice the calorie counts on menus, those counts also did not seem to have any impact on what they ordered and how often they frequented the restaurant, New York University Langone Medical Center researchers found. They presented their findings at the annual meeting of the Obesity Society.

Researchers looked at the lunch and dinner receipts from more than 2,000 patrons of Burger King and McDonald's restaurants in Philadelphia before and after the city's calorie labeling law went into effect in February 2010; these patrons were also asked if they noticed the calorie counts on the menus, whether that influenced their purchasing decisions, and how often they'd already had fast food from a big chain that week.

Random phone surveys were also conducted with residents of the city, which asked if residents ate fast food from any big chains in the last three months, and the frequency with which they ate it.

Less than half of patrons who visited the Burger King and McDonald's restaurants noticed the calorie labeling -- 49% at Burger King, and 34% at McDonald's, researchers found.

Plus, there did not seem to be a difference in the number of times people ate at the restaurants from before and after the labeling law went into effect -- people ate fast food about five times a week -- nor was there a decrease in visits to fast food restaurants, post-labeling law. (Researchers were able to find this by comparing their data with survey responses from customers of similar demographics at McDonald's and Burger King in Baltimore, which does not have mandatory calorie labeling at fast food restaurants.)

"What we're seeing is that many consumers, particularly vulnerable groups, do not report noticing calorie labeling information and even fewer report using labeling to purchase fewer calories," study researcher Dr. Brian Elbel, an assistant professor of Population Health and Health Policy at the NYU School of Medicine, said in a statement. "After labeling began in Philadelphia, about 10% of the respondents in our study said that calorie labels at fast-food chains resulted in them choosing fewer calories."