Confused by this week's news that a low-fat diet might not help prevent cancer and heart disease after all? Beth Hobson was.
"I've been on a low-fat diet for four years now," said the 44-year-old part-time worker at a fitness center in Pasadena, Md. "Does that mean I can go back to eating full saturated fats? I should go home and eat a pizza tonight?"
By no means, scientists said Wednesday.
The real culprits in our diets, they say, are the hardened fats present in margarine and shortening, as well as saturated fats in meat.
In addition, people seeking healthy lifestyles should look beyond eliminating fat and actively incorporate more fruits, vegetables, whole grains and exercise.
"It's all about balance in all ways," said Dr. Jacques Rossouw of the National Heart, Lung and Blood Institute.
Nor should people who are adjusting eating habits to prevent bad things from happening expect quick results. "The effects of a change in diet are going to take a long, long time," he said.
Rossouw was project director of a $415 million study in which 48,835 post-menopausal women ages 50 to 79 were assigned to eat either a low-fat diet or anything that they wished.
Researchers following the women over eight years found no statistically significant differences between the two groups in rates of colon cancer, breast cancer, heart attack and stroke -- all the things that doctors hoped a healthy diet would prevent.
The study in this week's issue of the Journal of the American Medical Association surprised and puzzled many consumers who are growing weary of shifting advice about food.
"Whenever I try to pursue some nutritional strategy, it seems that there's always some new study that comes out years later, reversing it," said Betty Boyd, a 32-year-old freelance writer from Baltimore.
Not so fast, said Cheryl Anderson, a nutritional epidemiologist at the Johns Hopkins Bloomberg School of Public Health.
"It would be absolutely a mistake to think that you can just eat what you want and you're going to be OK," said Anderson, who collaborated with Dr. Lawrence J. Appel, a Bloomberg colleague, on a JAMA editorial.
"If you're only watching total fats, you may miss the subtlety of what types of fats you're eating."
Like many other scientists, Anderson noted that the study was conceived before evidence emerged that two particular types of fat might be the chief dietary evils in heart disease.
One, called trans fat, is created when hydrogen is added to vegetable oils that harden into margarine or shortening. Trans fats are often used in commercial baked goods such as doughnuts, pastries and cookies. They also show up in the french fries and fried chicken made by most fast-food chains.
The other, saturated fat, is usually solid at room temperature and comes mostly from animal sources in meat, poultry, and whole milk and whole-milk cheeses. Saturated fats are also found in certain plant oils, such as palm, palm kernel, coconut oils and cocoa butter.
Both types of fat contribute to elevated blood cholesterol levels and increase heart disease risk, research has found.
A strategy that simply cuts back on all dietary fats -- as the women in the federal study did -- ignores this distinction and other knowledge that experts say they've gained.
"Ten years ago, our mind-set was to lower the fat -- the lower the fat, the better. That clearly has changed," said Dr. Michael Miller, director of the Center for Preventive Cardiology at the University of Maryland Medical Center.
More recently, he said, "Our approach has been not to restrict (total) dietary fats but to restrict saturated fats and to eliminate the absolute worst kinds of fats -- trans fats. Anything that says 'partially hydrogenated' on the box should be viewed as having a skull and crossbones.
"Seriously -- it's that bad for you."