McDonald's lovers won't walk away from a Big Mac -- even when they know its got 550 calories and 29 grams of fat in it. A new study in The American Journal of Public Health found that nutritional information displayed at McDonald's, Burger King and other fast food joints, has little effect on whether consumers Super-size their fries. Required by law in several states, the additional menu information goes largely ignored by fast food fans.

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In the Carnegie Mellon University study, more than 1,900 people were split into three groups. Group one was given no nutritional information, group two was given a flyer with daily recommended caloric allowances, and a third group was told that their per-meal calorie intakes should be between 600 and 800. Researchers found that despite being armed with more nutritional information, groups two and three didn't actually make better food choices.

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Why the cognitive dissonance? "In the end the bigger issue is that asking people to do math three times a day every day of their lives is a lot," said study author Julie Downs. "Because it's not like we make a decision about what to eat just once. It's a lot of decisions. And if you add a cognitive [mental] burden on top of that it's a lot to ask." So short answer? Math is hard. [Source]