Calorie consumption: Do numbers or graphics encourage diners to eat less?

"We find that either numbers or traffic lights have the same beneficial effect when it comes to taking in fewer calories," write the authors of the study, Eric M. VanEpps (Carnegie Mellon University), Julie S. Downs (Carnegie Mellon University), and George Loewenstein (Carnegie Mellon University). "In our particular study, either method resulted in food choices that contained 10 percent fewer calories."

To determine the effectiveness of numbers and traffic lights, the authors conducted a field experiment in which employees at Humana, a large health-care company, were asked to place lunch orders through an online platform designed especially for the study. A control group was given no calorie information. In the experimental group, employees were given either the number of calories, a traffic light indicating the approximate number of calories (a green light, for instance, meant the fewest calories), or both.

The study provides the most promising evidence to date that providing calorie information, either through numbers or icons such as traffic lights, encourages diners to take in fewer calories.

Although providing calorie information in the form of numbers may seem like the best option, policymakers should consider that not all consumers are adept at interpreting numbers. "For those consumers, traffic light labels can communicate basic 'eat this, not that' information regardless of their understanding of the underlying nutrients or ability to use numeric information," the authors write.