Traffic Lights and Food Choices


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Better food choices come from food positioning. Image by Alvimann.

Better food choices come from food positioning. Image by Alvimann.

Are you frustrated by food labels with tiny print? Does it annoy you when  healthy food items are hidden behind junk foods? What if identifying and locating healthy food during a busy lunch hour were easier?  Would you make better meal choices?

Dr. Anne Thorndike and colleagues from Massachusetts General Hospital and Harvard Business School set out to see if better food labeling and positioning change food choices.

Labeling: Or What Traffic Lights have to Do with Food

For the first three months of the 27 month study, researchers studied what people ate at Massachusetts General hospital’s cafeteria, a busy spot serving 2285 employees.

  • 75% of the employees were white, 10% African American, 8% Latino and 7% Asian.
  • 73% were female.
  • The average age was 43.
  • The largest percentage of employees, 58% were classified as “management/clinicians” with smaller numbers of technicians, professionals, support staff, and service workers.

After they collected the initial data, researchers labeled the all the cafeteria’s food. Items were marked with simple red, yellow, or green labels to indicate how relatively unhealthy or healthy a particular food choice might be.

The criteria for placing items in a particular category was based on the 2005 food pyramid. The researchers explain that they labelled every item “based on three positive criteria (fruit/vegetable, whole grain, and lean protein/low-fat dairy as the main ingredient) and two negative criteria(saturated fat and caloric content). Items with more positive than negative criteria were green, items with equal positive and negative criteria were yellow, and items with more negative than positive criteria were red.”

Zero calorie beverages were all labeled green.

Choice Architecture Intervention

The next step, which researchers called “choice architecture intervention,” involved making healthy items easier to find, such as  “rearranging items in the beverage and sandwich refrigerators to put all the green items at eye level; placing baskets of bottled water throughout the cafeteria;and providing prepackaged salads next to the pizza counter.

Researchers tracked purchases for another 24 months following the initial three month period.  Each day, the cafeteria sold an average of 16,834 items.

Design Strengths

The cafeteria research differed from many studies because it did not rely on self-report, but rather drew conclusions from objective sales data.  The 24 month time-span was also unique, allowing researchers to identify whether or not behavior persisted.

The Impact of Traffic Light Labeling and Choice Architecture

A traffic-light system easily identifies problem foods. Image by kconners.

A traffic-light system easily identifies problem foods. Image by kconners.

What happened? Employees changed their eating habits.  The percentage of red-labeled food that employees purchased decreased from 24% of items to 21% of items.  Purchases of green items went from 41% to 45%.

Most encouraging of all, the change was lasting – with the purchases at 24 months being somewhat healthier than at the 12 month mark.  Furthermore, all employees shared the healthy choices.  The authors write, “analyses of employee purchases by age and gender did not demonstrate any important differences.”

In an exclusive interview with Decoded Science, Dr. Thorndike admits, “when we started the project I was not sure that the changes in purchasing behavior would stick over the two years, but I am now convinced that our results demonstrate these types of labels can have lasting effects.

Food Labeling and Healthy Choices

Dr. Thorndike summarizes the work this way, “[c]urrent food labels require literacy and numeracy skills to interpret, and they can take a lot of time to read.  Having a system that conveys some basic nutrition information quickly, whether you are at a cafeteria, the grocery store, or a restaurant, can help a larger proportion of the population make healthier food choices.”

In a world of increasingly overweight and obese people who suffer from a variety of life-style diseases, simple changes in how food is presented could make an impact on our waistlines and health-care costs.

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