Does Posting a Calorie Count Change How People Eat?

Some time ago, we wondered if New York City’s new law requiring certain restaurants to post calorie counts might provide good material for academic researchers who care about obesity.
The answer: yes!
Brian Elbel, an assistant professor of medicine and health policy at the NYU School of Medicine and the NYU Wagner School of Public Service, was the lead researcher on a new study called “Calorie Labeling and Food Choices: A First Look at the Effects on Low-Income People in New York City” (abstract here; pdf here).
Elbel sent researchers into the field to measure the caloric habits of low-income people who eat at fast-food restaurants including McDonald’s and KFC. They gathered data before the calorie-posting law went into effect, in order to measure the change, and in addition to gathering data from New York fast-food restaurants, they also gathered data from equivalent restaurants in Newark, N.J., which doesn’t have a caloric-posting law, to serve as a control.
What did they learn?

“We found that 27.7 percent [of people] who saw calorie labeling in New York said the information influenced their choices.”

Great news, right? Um, no:

“However, we did not detect a change in calories purchased after the introduction of calorie labeling.”

Yikes. This is a great example of how well-intentioned incentives, even if they are successfully presented, fail to move the needle. There are obviously a million more questions to be asked in this realm. For instance:

• As nudges go, is this one simply too subtle? How might a calorie nudge compare to a price nudge (some kind of a fat tax — on fatty foods, that is, not people)?
• How might the response to caloric postings affect the choices of middle- and upper-income people?
• If you want to curb obesity, especially among lower-income people, what do you do if it turns out that lower-income people are less responsive to the calorie nudge than other people?
• Since this particular study relied on the subjects’ participation — the researchers intercepted them, inspected their receipts, and talked to them about their buying choices — what should we think about how representative these participants are? We write a good bit in SuperFreakonomics about how participants in most experiments are a) not likely representative of the general population — i.e., they are more cooperative — and b) likely to be influenced by the observers’ scrutiny and approval.

Personally, I think the calorie-posting law isn’t a bad idea at all. But I suspect that the people who will be most responsive to it, especially in the long run, are those who are already the most vigilant about their health and well-being. Think of it this way: what if the safest drivers on the road were the only ones to wear seat belts?