Calorie labeling on menus may help customers count calories, but it doesn't necessarily result in customers consuming fewer of them, according to a study by researchers at the Yale School of Management and New York University. The study examined the initial results of New York City's July 2008 legislation mandating restaurants to post calorie counts on menus. The findings may influence future efforts to address obesity through legislation.

Researchers gathered data before and after the calorie labeling went into effect, analyzing sales receipts and survey responses from 1,156 adult customers of four of the biggest fast-food chains—McDonald's, Burger King, Wendy's and KFC. The researchers gathered data in New York City and, as a comparison, Newark, N.J., which does not require calorie labeling.

In New York City, 27.7 percent of customers reported that the calorie information influenced their food selection, and of these, 88 percent claimed it led them to buy more healthful items. According to sales receipts, however, customers did not actually purchase lower-calorie foods. New York City customers purchased 825 calories on average before calorie labeling went into effect and 846 calories on average afterward.

But the authors of the study don't believe the results necessarily demonstrate the futility of calorie labeling.

“The take-away isn't that menu labeling doesn't work, it's that it might not be effective in isolation,” said co-author Victoria Brescoll, assistant professor of organizational behavior at the Yale School of Management. “There needs to be other concurrent interventions, such as educating people about daily caloric intake.”