Food labels

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

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  • Mary MacVean

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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