Posting the calorie content of menu items at major fast-food chains in Philadelphia, per federal law, hasn't change purchasing habits or decreased the number of calories that those customers consume, researchers reported Friday at the Obesity Society's annual scientific meeting, held in Atlanta. 

The results echo those conducted by the same researchers among low-income neighborhoods in New York City before and after calorie-labels were mandated there in July 2008, lending more evidence to the arguments that micro-managing food choice in the name of awareness doesn't work for the intended group.

"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," says lead study author Dr. Brian Elbel, assistant professor of Population Health and Health Policy at NYU School of Medicine. "After labeling began in Philadelphia, about 10 percent of the respondents in our study said that calorie labels at fast-food chains resulted in them choosing fewer calories."

As part of an effort to encourage people to make healthier food choices, the Patient Protection and Affordable Care Act mandates that restaurant chains with 20 or more locations nationally must post the calorie content of all regular food and drink items on their menu board or printed menus.

Yet there is limited scientific evidence from real-world studies to support calorie labeling. Moreover, little is understood about how calorie labels will impact different populations. Obesity affects more than one third of Americans, but hits low-income, urban neighborhoods hardest. "Studies have not generally examined whether labeling is more or less effective for particular subgroups," says Elbel.

Elbel and team set out to assess the impact of calorie labels at fast-food chains in the wake of the new legislation. In their latest study, conducted in Philadelphia, researchers collected receipts from more than 2,000 customers, ages 18 to 64, who visited McDonald's and Burger King restaurants during lunch or dinner before and after February 2010, when the calorie-label law went into effect in Philadelphia. 

Each customer was asked a short series of questions, including how often they had visited "big chain" fast food restaurants in the last week; whether they noticed calorie information in the restaurant; and if so, whether they used the information to purchase more or less food than they otherwise would have at the restaurant.

The research team also commissioned a professional survey firm to simultaneously conduct a random phone survey of residents within the city limits of Philadelphia. Respondents aged 18 to 64 were asked a series of questions, including whether they had consumed any "big chain" fast food within the last three months. If they had, they were asked a series of additional questions about how often they eat fast food, along with demographic questions and their height and weight.

The researchers found that only 34 percent of McDonald's customers noticed the labels posted to menu boards, compared to 49 percent of Burger King customers. Respondents with less education (high school or lower) were less likely to notice the labels. Moreover, respondents reported eating fast food more than 5 times a week, both before and after the labels were posted. There was no decrease in visiting fast food restaurants reported after calorie labeling began in Philadelphia.

(As a control, the researchers also surveyed customers of both chains in Baltimore, where calorie-labels are not mandated. About 70% of the customers surveyed in both cities were African American.)

"We found no difference in calories purchased or fast-food visits after the introduction of the policy," says Dr. Elbel. "Given the limits of labeling reported here and in other studies, it's clear that just posting calories is often not enough to change behavior among all populations. We need to consider other, more robust interventional policies in places where obesity is most prevalent."