NYC’s Trans Fat Ban Worked: Fast-Food Diners Are Eating Healthier

In 2006, New York City passed a first-in-the-nation ban on trans fats in restaurant food. Here's how it worked

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Elevated View of a Tray With Fries, a Hamburger and Lemonade

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 after the ban.

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.

The study by researchers in the New York City Department of Health and Mental Hygiene compared the lunchtime meals of people eating at fast-food chains around the city in 2007 and 2009 — before and after the trans-fat ban went into effect. In 2009, the average diner’s fast-food meal contained about 2.4 g less trans fats, down to about half a gram of trans fat per meal. More people also bought menu items with 0% trans fat after the restriction went into place, representing an 86% increase in these healthier options over a two-year period.

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 the partially hydrogenated oils used widely in the preparation of prepackaged foods and restaurant fare, such as commercially baked goods and fried foods like French fries.

In 2006, the federal government began requiring packaged food makers to list the amount of trans fat contained per serving, which was helpful for grocery-store shoppers comparing the relative heart-healthiness of processed foods. But the federal rule had no bearing on restaurant meals, which accounts for about a third of the total calories Americans consume each day.

New York City was the first in the nation to pass a ban against the use of artificial trans fats in restaurants, requiring food preparers to reformulate recipes or eliminate certain ingredients, so that their fare contained no more than 0.5 grams of trans fat per serving.

That’s why the current study’s results are so encouraging, says co-author Christine Curtis, director of nutrition strategy programs in the New York City Department of Health, especially in light of another proposed citywide ban against large-sized sugary sodas. “We hope this makes it clear that there is an opportunity for local jurisdictions to protect the health of their consumers,” she says.

(MORE: The New York City Soda Ban, and a Brief History of Bloomberg’s Nudges)

The study looked at the dining habits of people eating at 168 restaurants around the city, representing 11 fast-food chains, such as McDonald’s, Burger King, Subway, Au Bon Pain, KFC, Pizza Hut and Taco Bell, among others. Researchers compared 6,969 lunchtime receipts collected in 2007 with 7,885 purchases at the same restaurants in 2009, a year after the trans-fat ban was fully in effect.

The researchers studied fast-food diners in both high-income and low-income neighborhoods, but found no difference in the pattern of purchases made in either location. That suggests that it may be health concerns, more so than financial ones, that influence certain eating decisions even in lower-income areas, an encouraging sign for the implementation of public policy approaches to improving health.

The scientists also found that nutritionists’ worries that the trans-fat ban would just lead restaurants to swap trans fats for other unhealthy fats were unfounded; although consumption of saturated fat increased slightly, people ended up eating less combined trans and saturated fat after the policy went into effect. That means that people were eating less fat overall, and therefore consuming potentially healthier options.

Further, the findings proved that the reduction in trans fat consumption wasn’t simply resulting from smaller portion sizes. The ban allowed restaurants to come up with different ways to meet the 0.5 g-per-serving limit, including reducing portion sizes. But some restaurants reformulated their menu items to contain less trans fat, while others discontinued trans-fat-laden items altogether and replaced them with healthier products.

The biggest drop in average trans fat consumption occurred in burger chains, thanks to a combination of reformulated menus and changes in cooking practices, such as trading partially hydrogenated oils for trans-fat-free oils when frying. After hamburger chains, Mexican-food and fried-chicken chains saw the biggest drops in customers’ trans-fat consumption.

The study did not track diners long enough to see if their lower-fat choices translated to actual health gains, such as a drop in heart disease or obesity, but other studies show that such benefits are possible. Previous trials have linked even a 40-calorie-per-day increase in trans fat intake to a 23% higher risk of heart disease. And based on the data collected in the current study, Curtis says the average diner was eating about 20 calories less per day in trans fats. “That gives you an idea of the potentially big impact this policy can have on heart disease,” she says.

The American Heart Association recommends that people limit trans fat to less than 2 g a day, while the latest government dietary guidelines advise people to eat as little trans fat as possible.

New York City’s local ban has led to some wider benefits, since national chains like McDonald’s ended up reducing trans fats systemwide. So far, 15 other jurisdictions have taken New York’s lead and restricted trans fats as well, but Curtis hopes her study’s results will inform yet more legislatures about how powerful such policies can be.

Alice Park is a writer at TIME. Find her on Twitter at @aliceparkny. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME.