Artificially produced trans fatty acids—or partially hydrogenated oils—had been part of the American diet since the early 20 ^th century. They gave foodstuffs a long shelf life, provided stability during deep-frying, and enhanced the taste of baked goods and sweets. For decades, they were the food industry’s darling: in the 1970s, margarine was vigorously promoted as a healthier alternative to butter.

But in the 1990s, new studies showed that trans fats, as they were commonly known, might be dangerous.Further research confirmed that trans fats caused an increase in “bad” cholesterol and decreased “good” cholesterol, creating an increased risk of heart disease. By the early 2000s, the verdict was in—trans fats were a public health risk that contributed to heart disease. They were, unfortunately, everywhere—in the grocery store, at the school cafeteria, at high-end restaurants.

In 2004, Dr. Lynn Silver was named Assistant Commissioner, heading the Bureau of Chronic Disease Prevention and Control at the New York City Department of Health and Mental Hygiene. Combatting heart disease was high on her agenda because, in New York City, it was the leading cause of death—with even higher rates in the boroughs of Brooklyn, the Bronx, Staten Island and Queens than in Manhattan. One of the first issues Silver looked at was trans fat, a subject her predecessor had identified as a possible target for a public health policy change.

As much as a third of trans fat consumed in New York came from restaurant food.In spring 2005, Silver and her team decided to ask restaurants—as a public good—to change the way they prepared food. The department launched a highly visible public education campaign with the hope that pressure from customers, along with the desire to do the right thing, would persuade restaurants to stop using trans fat. But a year later, a survey revealed no change—its presence in restaurant food remained stubbornly high.

Silver concluded that it was time to take the next step: make the restriction mandatory, and restrict trans fat. The team began work on a regulation that would be both enforceable and fair. They had to decide: should the policy be informational or restrictive? Whom would it cover, and would it apply to all kinds of trans fat? What would be the maximum allowed trans fat in any product? How long would they give eating establishments to comply? What would be the sanctions for violations?

The team anticipated strong opposition from restaurant owners. They knew there would also be charges of a “nanny state”—government intrusion into the private decisions of citizens. But their first hurdle was closer to home. Both New York City Health Commissioner Thomas R. Frieden and Mayor Michael Bloomberg would have to sign off on the proposed regulation before it could go to the Board of Health for final authorization. They would want ironclad assurances that the science supported what would likely be a difficult sell politically.