A recent study from the University of Glasgow in Scotland successfully linked calorie labeling on menus with reduced weight gain for the first time. 

Over the course of 36 weeks, a group of students given no calorie information gained eight pounds on average. The following year, a separate group was presented with prominently displayed labels on their dinner menus and at the serving point where they received their meals for another 36-week period. The latter group gained only four pounds on average—a decrease of Sc50 percent.

The results were presented Nov. 5 during the Obesity Journal Symposium at The Obesity Society’s annual meeting in Boston.

“We used prominent calorie labels—big and colorful—so they could not really be missed by the students,” said Charoula Nikolaou, lead author of the study and a Ph. D. student at the University of Glasgow’s School of Medicine. “All previous calorie labeling studies used quite small information—they’re supposed to be the same size as the price [of the meal].”

About a dozen studies have looked at the relationship between calorie labeling and weight gain in U.S. chain restaurants and have seen little to no effect, according to Sara Bleich, associate professor of Health Policy at the Johns Hopkins University Bloomberg School of Public Health and spokeswoman for The Obesity Society.

“I think the biggest challenge for people is they don’t make a lot of sense of calorie information,” Bleich said. “Most people don’t know how X number of calories in a particular item would fit into a recommendation of about 2,000 calories per day. Even given that calorie benchmark, expecting people to make those calculations at the point of purchase is unlikely.”

Bleich said pre-packaged foods research shows that consumers do not have a good sense of nutrient compositions, vitamin content or even how to properly read a label. When it comes to ordering from a menu, consumers are expected to not only understand what the nutrition content of the meal is but also how the calories will fit into daily recommendations. 

According to Nikolaou, calorie content is generally related to fat content. By displaying the number of calories in a meal, students were automatically being nudged away from higher-fat meals. The researchers also analyzed micronutrient information and found that the lower-calorie meals were no worse in terms of vitamin and mineral content. 

“We had some anxiety they’d end up with unbalanced meals if they just focused on calories,” said Mike Lean, professor and chair of Human Nutrition at the University of Glasgow. “But because of the emphasis on meals, not pieces of a meal, that tended not to be true.”

Although calorie labeling is not a  treatment for obesity, it is a form of primary prevention that has been severely lacking worldwide, according to Lean. Research shows the trajectory of weight gain is set in early adolescence, rising in the teenage years and early adulthood before leveling off later in life. 

“Education has shown itself not to be effective, which is why food companies are very happy to put out a lot of educational materials—it doesn’t change the way people choose,” Lean said. 

Nikolaou called it “changing the architecture around food choices,” or redefining the factors that influence how people determine what food to order. Lean said the labels are not big enough or prominent enough to impact customers in New York City, where calorie labeling is legally mandated in franchised restaurants. The ambiguous results of prior calorie labeling studies seem to suggest that a highly-visible, daily reminder is necessary for successful results, he said.

During a portion of the second year of the study, the labels were removed from menus. Nikolaou said this removal of the constant reminder resulted in a slight increase in the calorie content of the meals students chose.

“They were relying on these labels, and if you took them away, even only for five weeks, they started to drift back,” Lean said. “They clearly did not automatically focus on the [meals] which we knew—but they didn’t know—to be lower in calories. They needed that regular nudge.”

Another important finding was that the caterers, who Lean said had been resistant to the labels at the onset of the study, ended up reducing their food costs by a third. 

“There’s a lot of nonsense out there, people saying that lower-calorie foods or healthier foods are going to be more expensive,” Lean said. “The answer is no. They can be, but they don’t have to be.”

While the participants were less apt to choose lower-calorie meals when the labels were removed, the low cost and daily nudging effect that calorie labeling provides may be able to influence long-term changes in consumer food choices, according to the study.

“We’re optimists,” Lean said. “Changing the environment on a daily basis results in people eating that little bit less and not gaining weight. I’m quite sure there is an entraining effect, but it’s probably minor. We need a permanent change in the environment of making food choices.”