It sounds like good public policy. But critics bemoan the lack of evidence showing that this and other initiatives will improve public health and make unhealthy eaters change their ways. Some researchers say the new laws and initiatives represent uncontrolled experiments that could backfire and end up having as many negative consequences as positive ones.

No one has ever conducted large-scale clinical trials to measure the effects of reducing salt intake in the general population, for example. The same is true for bans on trans fats, and few studies have looked at the calorie labeling requirement at restaurants.