Showing diners how many calories are in restaurant food items through symbols such as traffic lights coloured green, red and yellow depending on calorie count may influence how much they eat, according to a U.S. study.
That’s especially true among the least health-conscious people, said lead author Brenna Ellison, at the University of Illinois at Urbana-Champaign.
“To reach a broader group of diners, a symbolic calorie label may be preferred as it reduced caloric intake across all levels of health-consciousness,” she and her colleagues wrote in the International Journal of Behavioral Nutrition and Physical Activity.
Previous studies have found that people tend to eat less when they are told how many calories are in their food, but scientists had not looked at how that breaks down across different types of diners.
For the latest study, published in the International Journal of Behavioral Nutrition and Physical Activity, researchers randomized patrons at a restaurant on the Oklahoma State University campus to use one of three menus during a two-week period in late 2010.
One group of diners received standard menus without calorie information, another group got menus showing each item’s calorie count and the last group got a menu featuring traffic-light symbols representing calorie counts.
A green light was printed next to foods with fewer than 400 calories, yellow lights next to foods with between 401 and 800 calories, and red lights next to foods with over 800 calories.
By the end of the meal, diners ordering off the standard menu ate – on average – 817 calories. That compared to the 765 calories people ate when they ordered off the menu with printed calorie counts and the 696 calories they ate when ordering from the traffic-light menu.
Although that is only a difference of 52 calories and 121 calories between the standard and experimental menus, the study’s lead author said that can add up over time. Depending on the person, cutting 121 calories per day would lead to about a 554-gram (one pound) weight loss over a month.
“It could be substantial if that reduction persists every time you went out to eat,” Ellison said, though a one-time reduction would likely not have much impact.
Based on customer surveys, Ellison and her colleagues from the University of Oklahoma found that the least-health-conscious people seemed to cut the most calories in response to the experimental menus.
Those people are “precisely the people that menu-labelling laws are often trying to influence,” they wrote.
Regardless of how health-conscious people were, the traffic-light menu seemed to have the strongest influence.
“It’s encouraging because the information may help the people who will need it the most,” said Lorien Urban, who has researched menu labelling at the Jean Mayer USDA Human Nutrition Research Center on Aging at Boston’s Tufts University.
“I think it’s in line with what we’ve seen that interpretive information is helpful,” added Urban, who was not part of the study.
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