Two years after the fast-food chain's own deadline for reducing trans fats, the McDonald's French fry has thus far snatched defeat from the jaws of victory.

The chain had announced with fanfare that the amount of trans fats in its cooking oil would be cut almost in half by February 2003. After that, a more ambitious goal: It planned to eliminate this form of disease-causing grease, right down to the last McNugget.

Today, however, an order of fries is as trans-laden as ever.

"It's astonishing," says Michael Jacobson of the Center for Science in the Public Interest. He and many other nutrition experts feel burned for their accolades in September 2002, when McDonald's announced its intention. "If a big company holds a press conference, you'd think they would have planned things out."

They thought they had, says company spokesman Walt Riker. Despite the best intentions, McDonald's found that an oil change wasn't so easy.

One of the main problems was that the oil formulated in 2002 appeared to alter the famous taste of McDonald's fries.

The news is better for chicken lovers. McNuggets and other chicken products are now fried in an oil that is about 15 percent lower in trans fat.

Riker won't say when trans fats will be phased out. "It's still a work in progress," he says.

McDonald's has been using trans fats since 1990. At the time, the company was looking for a way to reduce the saturated fat and cholesterol coming out of its fryers. Trans fats are, before a chemical transformation, vegetable oil. The hope was that the trans fats would be no harder on health than canola or corn oil.

But the evidence against trans fat was already gathering, and it is now one of the major controversies in the American food industry. The new U.S. Dietary Guidelines urge Americans to keep their trans-fat consumption as close to zero as possible.

The problem is that trans fats have a singular ability to harm the heart and blood vessels.

"It's not something we were evolved to encounter," says Dr. Meir Stampfer from the Harvard School of Public Health.

What are trans fats?

Unlike most other forms of fat, the vast majority of trans fats are artificially made. They form when a liquid vegetable oil gets bombarded with hydrogen. The liquid becomes solid, giving baked goods a buttery feel in the mouth.

Partially hydrogenated oils, as trans fats are called, can extend the shelf life of manufactured goods. In the food industry, hydrogenated oils mean fryers don't have to be changed out as often.

These traits would all be easy to swallow if trans fats didn't also increase the odds of a heart attack. Both saturated fat and trans fat raise the level of LDL, the form of cholesterol that contributes to heart disease. But trans fat also lowers the level of HDL, which protects against heart disease.

Stampfer says research suggests trans fats increase triglycerides, a form of fat in the blood. Scientists began to suspect the danger of trans fat more than two decades ago. One landmark study in 1997 from Stampfer and colleagues found that women who consumed the highest levels of trans fat had a risk of heart disease about 30 percent higher than those who ate the lowest levels.

By 1999, the federal Food and Drug Administration voted to require trans fats to be listed on food labels, a measure that will take effect next year. A Congressional analysis estimates that a decade after the new labels appear — by discouraging trans fat use — they will yearly spare 7,600 to more than 17,000 people from heart disease.

The food industry has begun scaling back on trans fats. Texas-based Frito-Lay has removed trans fats from its products, as have many other major manufacturers. But few companies have the social and business weight of McDonald's. In 2002, experts were overjoyed that the world's largest restaurant chain had become an ally in the trans-fat war.

But February 2003 came and went with only a brief news release announcing an extension in the deadline. Months passed.

In September 2004, Jacobson's group bought full-page ads in The New York Times with the headline "A Broken McPromise." They skewered McDonald's, Jacobson says, because the chain "made the mistake of saying they were going to do the right thing, and then not doing it."

Still, the company has not put the effort on the back burner, Riker says. And he points out that McDonald's has taken other steps to make menus healthier, offering apple slices and salads, and reining in portion sizes.

Dr. Dean Ornish, for one, believes these moves aren't just public relations. For almost 30 years, Ornish has touted the benefits of a very low-fat diet. In 2002, he was one of the many experts who praised McDonald's for abandoning trans fats. He now consults for the company on ways to make its food better for the 23 million Americans who eat it each day.

"They remain committed to achieving the trans fatty acid goal," says Ornish, who runs the Preventive Medicine Research Institute in California. "The truth is that it was easier to reduce it in some products than others."

He says he understands why the company can't compromise the taste of its signature fries.

Supply is an issue

But there are other issues too, Ornish says. McDonald's has to make sure that an oil formulation has enough farmers to fill the supply. Once apples made it to the menu, McDonald's suddenly became the largest purchaser of apples worldwide, Ornish says.

So the company can't just fry its food in a different oil, which would be a natural way to reduce trans fat. Frito-Lay, for example, switched to cottonseed and corn oil. Canola oil would also work. However, Ornish says, there's not enough canola oil in the world to meet McDonald's' demand.

Researchers are scrambling to help McDonald's and others find ways to wean themselves off trans fats, says Robert Reeves, president of the Institute of Shortening and Edible Oils.

Some manufacturers, Reeves says, have moved to oils already available. Others are tinkering with ways to hydrogenate oils without creating quite so much trans fat in the final product, or altering oils through other means. Plant researchers are trying to develop varieties of oil seeds that produce more stable oils without need for hydrogenation.

What will work for each company, he says, depends on what kind of food they sell.

What remains, then, is McDonald's' French-fry challenge: pleasing the palate along with the arteries. Customers can only hope the final product will be golden.