After New York City passed a law requiring many chain restaurants to post the calorific value of all food they sold on their menus (in the same size and font as the price), researchers started looking at how the posting of calorie counts affect consumer decision making and food consumption.
The study’s findings, as summarised rather concisely in The New York Times, show that the law didn’t have the desired effect the legislators undoubtedly wanted:
It found that about half the customers noticed the calorie counts, which were prominently posted on menu boards. About 28 percent of those who noticed them said the information had influenced their ordering, and 9 out of 10 of those said they had made healthier choices as a result.
But when the researchers checked receipts afterward, they found that people had, in fact, ordered slightly more calories than the typical customer had before the labeling law went into effect.
Freakonomics author Stephen Dubner has his theory on the findings:
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?
Once you see the salad, realize it’s better for you and know that it’s an option, your inner sense of self-satisfaction is triggered, and then… you let yourself order fries, just because you were oh-so-smart enough to think about the salad, if only fleetingly.