Will reading the label help or hurt? Jesse Mactagone, 2 1/2 years, of Palo Alto, CA, in a Safeway store in Palo Alto, CA on April 12, 2000. (Bloomberg News/Jeff Carlick)

The FDA Nutrition Facts label, which tells consumers what’s in their packaged foods, is scheduled for a long-overdue update.

The new label, which the FDA hopes to roll out in the next two years, is being redesigned with new fonts and a new design, all intended to help people better understand what they’re eating.

The new labels will also include updated serving sizes to better reflect how much people typically consume. But this change may create a troubling unintended consequence: It could actually increase how much food people eat.

The change is consistent with the Nutrition Labeling and Education Act, which mandates that “serving sizes must be based on what people actually eat, not on what people ‘should’ be eating.” Because the serving sizes have not been updated in more than 20 years — during which time Americans’ average portions have ballooned along with their waistlines — most adjustments represent significant increases. For example, the serving size for ice cream will increase from ½ cup to 1 cup; for canned soup, from 1 cup to 2; and for a bottle of soda, from 8 ounces to 20 ounces.

This change should help people more quickly and easily determine how many calories and how much fat they consume if they indeed have 1 cup of ice cream, 2 cups of soup or 20 ounces of soda. However, research we recently published in the journal Appetite suggests the intentions of the proposed label could backfire.

Will consumers see the labeled serving size as a description or recommendation?

For starters, consumers might interpret the serving size information as a suggestion on how much food they ought to eat. In our study, we asked consumers what the serving size information on the Nutrition Facts label refers to. Less than 20 percent of people correctly thought the serving size refers to the amount of the product typically consumed in one sitting, while about 80 percent thought it recommended how much of that food they should eat. Yikes.

Even more concerning, our research found that the label caused people to eat more food. In one study, we asked people waiting in line for a college basketball game to participate in a taste test for chocolate chip cookies. We gave them a sheet with information about the cookies, and told them to try as many or as few cookies as they would like, but they should choose the number of cookies they would normally eat for a snack.

Unbeknownst to the basketball fans, half were given a sheet with the current Nutrition Facts label for the cookies, while the other half received a sheet with the proposed, updated Nutrition Facts label. People who saw the proposed label with its increased serving sizes ate 41 percent more cookies. Follow-up studies found the proposed label also led consumers to purchase and serve more food to other people.

These findings are troubling because excessive consumption is a key contributor to obesity. If reducing caloric intake is the goal, the FDA could consider ways to correct consumers’ misinterpretation of the proposed label. For instance, the FDA might add a serving size definition to the label, or add a statement to the label that says, “Serving size is not a recommendation; it may be healthier to consume less than the serving size in one sitting.”

This is especially important because the FDA has also proposed design changes to the label (such as changes to relative font size) that are intended to “drive [consumers’] attention to calories and serving sizes.”

How will consumers know whether to embrace or avoid particular food items?

Correcting consumers’ confusion about serving sizes is useful, but the FDA’s larger goal remains: guiding people to consume healthier amounts of nutritious food. For this, people might benefit from a label that allows them to quickly glance at packaging and know whether they should try to eat that food more or less often.

One practice in effect in Britain that may improve eating habits is simple: adding traffic lights to food labels. A red light would indicate unhealthy foods whose consumption should be tightly controlled. A green light would indicate healthy foods whose consumption is less important to control. A yellow light would be for the foods in between. A study conducted at a Massachusetts hospital by Dr. Anne Thorndike and colleagues found that adding traffic lights caused the proportion of sales of red, unhealthy items to decrease from 24 percent to 20 percent and the proportion of sales of green, healthy items to increase from 41 percent to 46 percent over two years. That might not be a dramatic improvement, but it’s a step in the right direction.

The Nutrition Facts label can be a powerful tool for helping consumers make healthier eating decisions. But consumers need a Nutrition Facts label they can correctly interpret and use to make healthier eating decisions.

Steven Dallas is a marketing Ph.D. student at New York University’s Stern School of Business. Peggy Liu is a marketing Ph.D. candidate at Duke University’s Fuqua School of Business. Peter Ubel is a physician and behavioral scientist at Duke.