A study of restaurant diners in New York shows that the city's ban on trans fats improved its residents' diet: fast-food customers chose healthier options and cut their trans-fat consumption.

It's promising evidence that such changes on a local level can make a meaningful difference in people's consumption — without even requiring them to change behavior significantly on their own. The study, published in the Annals of Internal Medicine, also shows that people reduced artery-clogging trans-fat intake after the ban, without replacing it with another type of fat.

An analysis of thousands of lunch receipts, collected at fast-food chains before and after the ban, estimates that the average trans fat content of customers' meals has dropped by 2.5 grams, from about 3 grams to 0.5 grams.

Trans fats are known to be particularly dangerous for heart health. Some trans fats occur naturally in dairy products and meat, but the majority of these fats in the average American diet come from partially hydrogenated oils in commercially baked goods and fried foods such as French fries.

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