PHILADELPHIA — Those seeking the keys to a healthy diet these days face a predicament.

Decades of studies have produced vast stores of data about the foods and nutrients likely to enhance and extend life. But any attempt to retrieve this vital knowledge lands the public in an informational crossfire.

Of all dietary staples, none has created as much fury as fat. How much, and what kind, is good for you? In the spring, the Annals of Internal Medicine published a paper concluding that saturated fats do not increase the risk of coronary disease. It also found no statistically significant health benefits from eating polyunsaturated vegetable oils.

The study made news. Big, sexy, controversial news.

“Everyone loves the idea that everything you thought you knew about nutrition is wrong,” said Marion Nestle, author of numerous books on food and a professor in the department of nutrition, food studies and public health at New York University.

The paper’s authors were cast by some as a sort of nutritional Innocence Project who had finally exonerated butter, lard and marbled meats, those dietary fiends long condemned as murderers.

The verdict, however, was by no means unanimous or clear-cut.

Statisticians, doctors, nutritional experts, journalists, biochemists and even some of the paper’s own authors continue to debate what the findings mean and what, if any, changes people should make in their diets.

They all agree on this much: Food pyramids that used to recommend restricting all fat intake to an ascetic minimum were misguided, and the result — a marked increase in the consumption of sugars and refined carbohydrates — has made Americans significantly less healthy.

Many of the same experts who established the previous national guidelines are advising the public to increase fat intake while cutting down on breads, cereals, potatoes, rice and especially “low-fat” products such as sodium-infused processed meats and salad dressings made with sugar and salt instead of vegetable oil.

Does this mean the road to cardiac health is paved with bacon-wrapped burgers?

Most nutritional authorities say, sorry, no.

“The message is not that butter is back, red meat is back,” said Dariush Mozaffarian, dean of Tufts University’s School of Nutrition Science and Policy and one of the co-authors of the Annals study. “No one said saturated fat is good for you, per se, as a class. No one is saying don’t eat fruits and vegetables. That is an incorrect interpretation of the findings.”

What the experts are saying, Mozaffarian explained, is that a healthful diet requires a wide variety of whole, natural foods, including many, such as cheese and nuts, that contain some saturated fat.