FDA researchers found people were best at assessing chips and frozen meals - and comparing the healthfulness of multiple products - when nutrition facts were presented for the entire container's worth of food or for both one serving and the whole container.
Those presentations don't require consumers to multiply the nutrition facts listed by the number of servings per package if they plan to eat it all, researchers explained.
"I think people really have a hard time interpreting what food labels mean," said Dr. Eric Matheson, a nutrition researcher from the Medical University of South Carolina in Charleston.
"It's almost like there's information overload," Matheson, who wasn't involved in the new study, told Reuters Health - but at the same time a lack of clear, simple messages.
Amy Lando and Serena Lo from the FDA surveyed close to 9,500 U.S. adults, showing them one of 10 different types of food labels that presented calories and nutrients per serving or container in a variety of ways.
Participants were asked how healthy they thought different products were - including how much fat, for example, was in one serving - and then compared two types of chips or frozen meals to determine which was healthier.
Currently, manufacturers are given a lot of leeway when it comes to deciding how much a "serving size" is, according to Gina Mohr, a marketing researcher from Colorado State University in Fort Collins, who didn't contribute to the FDA study.
To make products appear healthier, some companies have started increasing the number of servings listed per container - thus lowering the number of calories per serving. All of that adds to consumers' confusion, she said.
Having a two-panel system that lists the nutrients for one serving and an entire package - as some products do already - would help simplify things, Mohr told Reuters Health.
"It's so important to make the information as transparent as you can make it for consumers," she said.
Nutrition researcher Marion Nestle from New York University, who also wasn't involved in the new study, agreed.
"If you give somebody a big package of potato chips, they're not going to think there are five servings in it, they're going to think it has 100 calories," she told Reuters Health.
"I would like to see the total number of calories in a package on a package," Nestle added. "I don't think people should have to do the math."
Nestle and Matheson both recommended a system like Britain's, in which the front of food products are labeled green, yellow or red based on their healthfulness. Of course, companies might not be so happy about having their packages labeled red, they noted.
It's still not known whether clearer nutrition facts would change what people choose to buy or eat, researchers cautioned. It's also unclear if and when the FDA might issue changes to labeling requirements, based on the new findings and other research.
For now, researchers said consumers should look closely at nutrition information, including serving sizes and where the calories in their food are coming from.
"One thing we urge consumers to do is really slow down and read the information carefully on packaged foods," Mohr said.
"Turn it over, read the ingredients, read the nutrition facts carefully."
SOURCE: http://bit.ly/nODt9w Journal of the Academy of Nutrition and Dietetics, online January 23, 2013.