At the same time, there were so many unhealthy items on all the menus that the additions had no effect on average entree calories. And there was no effect on children's menus at all. In fact, the nutritional content of children's offerings was so bad that the researchers had to redefine "healthier" to even find dishes to count.
The results were a reminder of all the "ifs" about menu labeling. If consumers don't notice - or don't act on - what's posted, it does little good. On the other hand, if they not only see the information but absorb it for trips to the supermarket and cooking at home, the impact could be multiplied.
And if restaurants embrace rather than resist helping customers make healthier choices, the industry's marketing muscle could be a game-changer.
"It's great to see that national restaurant chains are making improvements to their menus from menu labeling being in effect in only a handful of jurisdictions. That gives me hope that there will be even more changes once menu labeling is in effect nationally," said Margo G. Wootan, nutrition-policy director for the Center for Science in the Public Interest, a Washington advocacy group, and a coauthor of the new study.
People consistently say they want to eat better but have a tough time doing it. Another new study, led by Harvard University researchers, found that adults and school-age children thought that their meals contained 175 fewer calories than they did; teens were off by 259 calories.
A third study asked customers for their receipts at 50 locations of 10 chains in King County (Seattle), Wash., both before and 18 months after menu labeling began there. It measured a 38-calorie drop in the average purchase.
That may not sound like much, said Wootan, but with the obesity epidemic turning on 150 or so calories a day averaged across the population, to cut that amount using one strategy at lunch "is quite a bit."
The fast-food industry, which has been strongly criticized for stuffing nearly a day's worth of fat and sodium into a single meal, often says it is giving customers what they want. If that's true, restaurateurs should be jumping on the nutrition bandwagon, said Hank Cardello, a former marketing director for the Coca-Cola brand.
"Healthier stuff sells," said Cardello, director of obesity initiatives for the Hudson Institute. The independent research group did a study this year of sales trends at 21 national chains from 2006 to 2011. In nearly every category - food servings, beverage servings, customer traffic, same-store sales - low-calorie offerings drove business up, while traditional meals were losers. "I look at that and I say, 'Hello, this is your growth vehicle here,' " said Cardello.
But he noted that low-calorie does not always mean healthy - and that adding healthy choices to the menu does not necessarily mean that restaurants want you to buy them. Some may just want "to be able to say that they are offering healthier options," said Giridhar Mallya, director of policy and planning for the Philadelphia Department of Public Health.
The new Drexel study on nutrition labeling compared online menus at five national fast-food chains with some outlets covered by local labeling laws against menus at four chains that were never in those locations before and after the regulations took effect.
New York City implemented the first calorie-posting law in the nation in 2008. Philadelphia added the most stringent law in 2010, requiring sit-down chain restaurants to also list saturated fats, trans fats, carbohydrates, and sodium beside every item.
The chains with some affected restaurants began adding to their menus just as the first laws took effect, the researchers found, with healthier items rising from about 13 percent of their offerings before 2008 to 20 percent in 2011. At the "control" chains, with no affected outlets, healthier offerings were unchanged at 7 percent to 8 percent.
The study's small size - the researchers could find only nine chains that met their criteria and listed full nutrition information online - may explain why the two groups were different to begin with, as well as the lack of change in average entree calories.
"Even though some of the restaurants added healthier fare, the same restaurant (or other restaurants in our sample) countered that by adding unhealthy items to the menu," coauthor Amy Auchincloss of Drexel's public health school said by e-mail.
The study was led by her former student Alexa Namba, now in her second year at Philadelphia College of Osteopathic Medicine.
The restaurant industry first fought hard against menu-labeling laws. As they spread to about 20 places nationwide, the industry changed course and embraced a uniform national rule, likely the reason that chains with outlets in some covered locations changed their menus in all.
The federal calorie-posting law became part of the 2010 health-care overhaul. Intense lobbying since then - over excluding supermarkets, cinema concessions, takeout pizza, and alcoholic drinks - has delayed a final rule.
Because the federal law preempts all local ordinances, Philadelphia has been unable to enforce its more comprehensive version, although inspections have found 85 percent voluntary compliance. And until final regulations are issued, the Food and Drug Administration won't consider the city's petition for an exemption.
Contact Don Sapatkin at 215-854-2617 or firstname.lastname@example.org.