A federal plan to encourage healthy eating by changing portion sizes on nutrition labels could have the opposite effect, according to new research from the Duke University Fuqua School of Business.
"It actually could cause people to consume more," Professor Peter Ubel said.
Proposed changes to the Food and Drug Administration's nutrition facts label — the first update in more than 20 years — include an increase in serving sizes to more accurately reflect how much Americans are consuming at each meal.
"It all sounds great and public health people are really excited about it," said Ubel, a physician and behavioral scientist who studies subtle influences on decision-making. "But we were worried it would tell people what they ought to eat. It would suggest to them that the appropriate serving size is what they're consuming."
Ubel and his colleagues Peggy Liu, also of Duke, and Steven Dallas of New York University, found in several studies that participants were likely to eat more after seeing the new labels.
The findings, "Potential Problems with Increasing Serving Sizes on the Nutrition Facts Label," are published online in the journal Appetite.
In one study, 101 participants were asked the meaning of the serving size on the nutrition label. More than 78 percent who saw the proposed labels with larger portions still incorrectly believed they referred to the appropriate amount to consume at one sitting.
"We were surprised by how frequently consumers misinterpreted the meaning of serving sizes," Dallas said. "Even though serving sizes are a staple of the Nutrition Facts label, people have no idea what they mean."
Further studies showed that misunderstanding can also affect behavior. The researchers asked 51 adults in line at a basketball game to choose the number of cookies they would normally eat for a snack. Those who saw the proposed labels, which listed a serving as six cookies instead of the old label's three, ate 41 percent more cookies than those who saw the current label.
Another study presented 61 participants with a family-size lasagna and were asked how many they would buy to feed 20 people at a dinner party, and how they would divide the meals.
The half of participants shown the proposed labels, which listed each lasagna as containing only three portions — instead of the six listed on the existing label — planned to buy 43 percent more lasagnas and created individual portions that were 22 percent larger.
"That shows there's a problem with this approach," Ubel said. "It's reinforcing the bad habits Americans have developed over the last few decades."
The researchers concluded any change to the label should also include a definition of serving size, so consumers understand it isn't a recommendation. But Ubel said what's ultimately needed is more emphasis on whether a food is healthy in the first place.
"I would try to shock people into the better choice and not try not to make this all about calculating calories," he said, "because that really doesn't go anywhere."