Slapping a calorie label on prepared foods at the supermarket only slightly helped shoppers cut back on ready-to-eat calories, according to a longitudinal study.
Among 173 supermarkets in the Northeast, calories from prepared bakery items purchased per shopping trip dropped by a mean of 5.1% (95% CI -5.8 to -4.4) after stores introduced calorie labels on products, reported Joshua Petimar, ScD, of Harvard Medical School and Harvard Pilgrim Health Care Institute in Boston, and colleagues.
There was an even larger reduction seen among prepared deli items, with new calorie labels spurring an average 11% (95% CI -11.9 to -10.1) drop in calories per transaction, the group noted in JAMA Internal Medicine.
While significant, these average reductions were generally small, equating to about 10 fewer calories per transaction from prepared bakery items, like muffins and donuts, and about 18 fewer calories from deli items, like meats and cheeses. There were no changes in average number of calories bought among prepared entrees and sides at the supermarket after calories were visible on the packaging.
Of note, shoppers didn’t compensate for this reduction in calories by buying more similarly packaged foods without calorie labels, the authors pointed out.
Even though the average declines were small, Petimar’s group remained positive about these changes, noting that “these declines could be meaningful at the population level given the ubiquity of calorie labels in retail settings, the frequency with which people consume prepared foods, and the growing market for supermarket prepared foods.”
However, in an accompanying commentaryMarion Nestle, PhD, MPH, of New York University, wasn’t quite as convinced, calling these tiny decreases in purchased calories “hardly enough to seem capable of having any influence on body weight.”
She also noted that these findings weren’t much of a surprise, as they fall in line with previous studies of labeling in fast food restaurants.
“Such interventions may have large effects on some people — I, for example, pay close attention to calorie labels — but their population-based benefit appears small,” she wrote.
A couple things are needed for this type of obesity-fighting policy intervention to really be effective, Nestle explained. First, people need to be aware of the number of calories they need in a day, as well as how the calories in specific items relate to that total — information that “many are likely to have,” she noted. But on top of that, the shopper also needs to be “willing and able to deprive themselves of attractive, delicious food when they have reached their total caloric needs” — something that is likely much harder for the average consumer.
“My interpretation of the current status of obesity prevention research is that any single policy intervention is unlikely to show anything but small improvements,” she concluded.
For this analysis, Petimar and team looked at supermarkets from one chain that had locations in Maine, Massachusetts, New Hampshire, New York, and Vermont. They compared sales during the 2 years before the chain implemented calorie labeling in the prepared foods section with sales 7 months after the change, accounting for 4,459,407,189 items purchased at all the stores over the study period from 2015 to 2017. Few of these transactions occurred online or using SNAP benefits.
Analyzes were adjusted for holidays, including during the weeks of Thanksgiving to Christmas, the week of Easter, and the week of Fourth of July, to reduce potential residual confounding.
This study was supported by the National Institute of Diabetes and Digestive and Kidney Diseases.
Petimar and co-authors reported grants from the National Institutes of Health and the Center for Science in the Public Interest.
Nestle reported no disclosures.