One of the less-noticed provisions of the Affordable Care Act requires calorie labels at all chain restaurants and similar retail food establishments, following similar efforts in New York City and elsewhere. A new study raises doubts about whether those labels will make much difference to public health. The right response isn't to abandon the effort, but to improve it, and consider new approaches.

The idea behind such labels is appealing and simple: Consumers don't know how many calories are in the foods they buy, and once they found out they'll probably make healthier choices. Some hamburger meals can exceed 3500 calories. Some pizzas? More than 2000. And there are major surprises. Avocadoes taste great but they're pretty fattening, and salad dressing and olive oil can have a load of calories.

The movement for calorie labels was spurred by research in 2010, when Stanford's Bryan Bollinger, Phillip Leslie and Alan Sorenson showed significant effects on consumer behavior. Studying 14 months of detailed data from Starbucks in New York City, they found that such labels produced a 6 percent decrease in average calories per transaction. Consumers bought fewer items, and they also made lower-calorie selections. Impressively, the effects persisted for the entire period of the study.

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Since 2010, however, studies have shown much more mixed results, especially in low-income communities. Some people have speculated that to many consumers, a calorie label just isn't terribly meaningful. A high calorie count might even make a product more attractive, on the theory that you want to get more rather than less with your money.

The most recent study, and in some ways the most comprehensive, was done by researchers at New York University, led by Jonathan Cantor, a doctoral student there. Focusing on fast-food restaurants in New York City, Canter and his colleagues used data from actual cash register receipts and from surveys, both in 2008 (when the city's mandate took effect) and at three points in 2013 and 2014. They concentrated on restaurants in low-income minority neighborhoods. For those who favor calorie labels, their results are quite disappointing.

In the immediate aftermath of the 2008 law, a majority of consumers (51 percent) did report seeing the labels. In the 2013 and 2014 period, that number decreased, though it remained relatively high (in the vicinity of 40 percent). But even in 2008, only 12 percent of people said that they used the labels to order few calories. That number fell to 9 percent in more recent years. Most significantly, the researchers didn't find a decrease in calories purchased as a result of the labels.

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As the authors note, their study has limitations. They didn't look at sit-down restaurants or a range of cities, or the effects of labels on higher-income consumers. (In that sense, their findings don't contradict the 2010 Starbucks study.) Some advocates of calorie labels believe that the long-term effects will be on not consumers but producers, who will offer healthier options. And one effect of calorie labels might be to lead some people not to go to fast-food restaurants at all; Canter and his colleagues didn't explore that possibility either.

At a minimum, the new research demonstrates the importance of continuing to track the effects of calorie labels, and also of asking what policy reforms might be helpful. As the researchers note, it might make sense for public officials to accompany the labels with a public awareness campaign, perhaps targeted to communities for which labels by themselves might just be background noise.

There are other possibilities. To make the numbers more meaningful, food selections could be ranked in terms of calories; such rankings have been found to have a major effect. Or consumers might be given information about how much exercise is needed to burn off a specific number of calories. Among African-American adolescents, this intervention has been found to help a lot.

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Major effects have also been found from a "traffic light" system, with color-coded labels: green (healthy), yellow (less healthy), and red (unhealthy). A team of researchers at Massachusetts General Hospital, led by Anne Thorndike, found that such labels produced substantial reductions in sales of high-calorie beverages and increases in sales of low-calorie ones in a large hospital cafeteria.

True, restaurants don't have particularly strong incentives to discourage people from purchasing some of their offerings. But as society increasingly focuses on obesity, innovative approaches are worth considering -- and if restaurants decline to consider such approaches on their own, governments may eventually encourage them to do so. As for the mixed evidence for calorie labels, the central lesson is this: The most effective disclosures tend to be simple and meaningful to consumers. The latest efforts should be mended, not ended.

Cass Sunstein, a Bloomberg View columnist, is director of the Harvard Law School's program on behavioral economics and public policy.