"When we are done we will probably see 20 percent change in the food supply in a year," Popkin says. "The food supply is changing and no one really knows how."
For example, the researchers have found that there has been an increase in using fruit concentrate as a sweetener in foods and beverages because of a propensity toward natural foods, even though it isn't necessarily healthier than other sugars. While the soda and chocolate milk have more calories on average than the government thought, the federal numbers were more accurate on the calories in milk and cereals.
Popkin and his researchers are hoping their project will only be the beginning of a map that consumers, companies, researchers and even the government can use, breaking the data down to find out who is eating what and where they shop. Is there a racial divide in the brand of potato chips purchased, for example, and what could that mean for health? Does diet depend on where you buy your food — the grocery store or the convenience store? How has the recession affected dietary intake?
"It's only since I've really started digging into this that I have realized how little we know about what we are eating," says Meghan Slining, a UNC nutrition professor and researcher on the project.
Steven Gortmaker, director of the Harvard School of Public Health Prevention Research Center, says the data could help researchers figure out how people are eating in certain communities and then how to address problems in those diets that could lead to obesity or disease.
"The more information we have, the more scientists can be brainstorming about what kinds of interventions or policy changes we could engage in," Gortmaker said.
But the information doesn't include restaurant meals and some prepared foods, about one-third of what Americans eat. If the project receives continued funding, those foods eventually could be added to the study, a prospect that would be made easier by pending menu labeling regulations that will force chain restaurants to post calories for every item.
Popkin and his researchers say that packaged foods have long been the hardest to monitor because of the sheer volume and rapid change in the marketplace.
The Healthy Weight Commitment Foundation, an industry group representing the 16 companies that made the pledge to reduce 1.5 trillion calories, says it will report this summer on how successful they've been, according to Lisa Gable, the group's president. The first results from Popkin's study aren't expected until later this year.
Marion Nestle, a New York University professor of nutrition, food studies and public health, says the data could be useful in pressuring companies to make more changes for the better. Companies often use "the research isn't there" as a defense against making changes recommended by public health groups, she notes, and it can be hard to prove them wrong.
"What people eat is the great mystery of nutrition," Nestle says. "It would be wonderful to have a handle on it."
UNC Food Research Program: http://uncfoodresearchprogram.web.unc.edu
Healthy Weight Commitment Foundation: http://www.healthyweightcommit.org