‘Traffic light’ food labels changed buying habits, study finds

This box shows the idea of "traffic light" labeling in the lower right corner. The logos come from various sources.

Would you fill that 16-ounce cup with sugary soda if it had a red light on the dispenser? Or might you move to the faucet for water and its green light? Researchers tracked food and drink choices in a big Boston hospital and found that those “traffic light” signals influence choices, even for two years.

It’s long-term change that many experts trying to reverse the obesity epidemic consider the brass ring. The notion of making the healthy choice the easy choice — such as a traffic light system that doesn’t require label reading — has gained some currency.

The researchers reported Tuesday in the American Journal of Preventive Medicine that sales of “red” foods decreased from 24% of food sales at the start to 20% at two years; red beverages went from 26% of beverage sales to 17% at two years. Green foods sales grew from 41% to 46%, and green beverages from 52% to 60%.

“These results suggest that simple food environment interventions can play a major role in public health policies to reduce obesity,” the researchers wrote.


Employees of Massachusetts General Hospital and everyone who used the cafeteria were tracked; there was an average of 6,511 transactions a day.

Preventing obesity will require a change in the food “environment,” the researchers, a team from the hospital, reported. That means that healthful, lower-calorie foods are more readily available and encouraged than higher-calorie, unhealthful foods.

The traffic light signs are one way to do that, and every item in the cafeteria got a red, yellow or green designation. Another tactic the researchers used was to rearrange the cafeteria to encourage particular purchases. So salads were put near the pizza, green-light items were stocked at eye level. The mix of food sold was not changed.

“It is critical to evaluate the long-term effectiveness of food environment interventions,” the researchers wrote. Previous work has shown that such interventions in a hospital cafeteria worked for six months, among employees and everyone who used the cafeteria. Some had questioned whether people would tire of the labels and stop noticing them after a while.

A strength of this study is that the purchases were tracked, rather than self-reported. A weakness is that it occurred in one hospital in once U.S. city.

The researchers contend that the food industry can take part in the fight against obesity without compromising profit; they said that the traffic lights and shelf changes didn’t harm total sales.


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