In July 2008, New York City began requiring chain restaurants to list calorie counts on their menu boards. The first study of this mandate's impact, published online yesterday by the journal Health Affairs, suggests that, contrary to the highly optimistic projections of its promoters, it has not led New Yorkers to consume fewer calories. In fact, the researchers found that the average calorie count for meals at fast food restaurants (McDonald's, Burger King, Wendy's, and KFC) rose by 2.5 percent in New York after the mandate took effect while remaining essentially unchanged in Newark, the comparison city.

Using a combination of interviews and data taken from diners' receipts, the researchers were able to measure the correspondence between what people said and what they did, which was less than perfect. The share of New York diners who said they noticed calorie counts rose dramatically after the menu mandate kicked in, from less than 20 percent to 54 percent (much bigger than the increase in calorie awareness observed in Newark). But less than a quarter of those who reported seeing calorie information said it led them to consume fewer calories. While this subgroup (13.5 percent of all subjects) ate less, on average, than the overall sample, they ate more than the diners who said they did not notice calorie counts. "Even those who indicated that the calorie information influenced their food choices," the researchers write, "did not actually purchase fewer calories."

This study covered four weeks, two before the calorie counts appeared and two afterward. Maybe the newly conspicuous information needed more time to have an impact, though it's hardly encouraging that even the people who claimed to have changed their behavior in response to the calorie counts did not actually eat less. It's also possible, as the authors suggest, that research focusing on affluent white people, as opposed to the poor blacks and Hispanics sampled in this study, might find evidence of an effect. Another limitation of the study is that it did not consider people who may have been driven away from fast food chains by the calorie counts. But it's not clear that such customers ended up eating less elsewhere; they may simply have sought restaurants where they would not be reminded of how many calories they were consuming. 

In any case, it seems clear that menu mandate boosters have exaggerated this policy's power to make people thinner. The New York City Department of Health and Mental Hygiene predicted the menu regulations would stop 150,000 people from becoming obese and prevent 30,000 cases of diabetes over five years. The California Center for Public Health Advocacy claimed menu labeling would result in a weight loss of nearly three pounds a year per fast food consumer. Such results are hard to achieve if people do not actually eat less.

The main problem is that information accomplishes nothing unless people are motivated to use it. Since fast food chains were already providing calorie counts on their websites and on posters, tray mats, and flyers in their restaurants, weight-conscious customers had this information even before New York decreed that it appear on menu boards as well. The impact of making it more conspicuous therefore would be limited to the customers who are least inclined to use it.

I criticized New York's menu mandate when it took effect.

[via Ryan Sager]