Is the Low-Fat, High-Carb Diet Mantra a Myth?

— -- In the fight against fat, Noreen Hunter is a battle-scarred veteran. For most of her life she has struggled to lose weight with one low-fat diet after another.

Hunter, 46, did lose weight, but she always gained it back. In the past year alone she has regained 50 pounds. No wonder she's thrown in the towel and is now trying a diet that seems sinful. It's high in fat and low in carbohydrates.

But to do this, she's had to get over years of brainwashing that says fat is bad. "You have to de-program yourself to thinking in a different way, that maybe something else is going to work."

Hunter is part of a diet revolution that is sweeping the country. That's because for the past 30 years, while Americans have been religiously following low-fat diets, they've actually been getting fatter.

But "What If Fat Doesn't Make You Fat?" asks science writer Gary Taubes in a recent New York Times article in which he addresses what he considers the bad science that's lured millions to low-fat diets.

"What we believe to be true with such certainty could just be a sort of mass delusion, wishful thinking that the medical establishment inflicted on us, and it just snowballed," Taubes told 20/20 in an interview with ABCNEWS medical editor Dr. Timothy Johnson.

"The theory was that a low-fat/high-carb diet would control weight and help prevent killer diseases. But most of the studies that followed actually failed to show a direct link between fat in the diet and heart disease and cancer. But by then it was too late — even science couldn't shake the prevailing wisdom that all fats are bad, and all carbs are good," explained Johnson.

By investigating the genesis of this theory, Taubes found that the government's initial decision 30 years ago to promote low-fat diets was not based on recommendations from doctors or scientists, but rather from lawyers who worked for Sen. George McGovern in the mid-1970s.

"They come out with this document and it just sets this ball rolling where finally some government body is telling Americans to eat less fat and eat more carbohydrates," Taubes said.

With the release of the government's "Food Pyramid" in the early 1990s, it was official: the low-fat/high-carb diet was America's food plan.

At the pyramid's base are the foods considered the staple of the healthy low-fat diet: refined carbohydrates such as bread, cereal, rice and pasta. At the narrow top — indicating that they should be used sparingly, if at all: fats and oils.

There were, however, some lonely voices of opposition.

For one, Dr. Robert Atkins, the now-deceased low-carb guru, said the government had it all wrong.

The Atkins diet approach, which allows unlimited protein and fats including meats, cheeses, eggs and butter, eaten along with very limited quantities of all types of carbohydrates — even fruits and vegetables — is based on the body's ability to switch its metabolism from a carb-burning mode to a fat-burning mode once carbs are eliminated.

Most nutritional experts are wary of Atkins' extreme recommendations because of the dramatic, and possibly hazardous, changes his diet can have on the body. Among the many concerns are possible vitamin deficiencies, dehydration, gastrointestinal problems, and kidney, heart and gallbladder disease.

"We need to know much more before people start making claims. … Shouldn't diet doctors prove safety first, rather than write books and then say 'OK, prove harm,'" comments Keith Ayoob, spokesperson for the American Dietetic Association and associate professor of pediatrics at Albert Einstein College of Medicine in New York.

In the last decade, however, several leading nutritional scientists have begun to think Atkins may have neen partly right about carbohydrates, and scientists are now finally studying whether low-fat diets really work.

"I think it's quite clear that he's onto something important. It does seem that this substantial reduction in carbohydrate for many people does make it easier to control their diet over the long run," says Dr. Walter Willett, chairman of the department of nutrition at the Harvard School of Public Health.

Moreover, following the low-fat/high-carb diet of the U.S.D.A. Food Pyramid may not only make it difficult to control weight, it could actually be dangerous, according to Willett.

"The dietary pyramid was out of date the day it was printed, but it's even more out of date given the evidence that's accrued since that time," said Willett. "We have good evidence now that the high intake of refined starches and sugars will increase risk of diabetes and heart disease," he added.

Years of diet studies done by Willett and others have apparently found that healthy people tend to do two things: they actually increase "good fats" and "good carbohydrates" while cutting down on both "bad fats" and "bad carbohydrates."

"And here is the big pay-off from a good fat/good carb diet. Not only is it more likely to be healthy. It may also make it easier to control our weight. That's because sugars and starches get quickly absorbed into our blood stream and lead to sudden spikes in insulin levels — which leads to low blood sugars and increased hunger, which make us eat more," said Johnson.

That's why many experts now believe that a diet high in bad carbs actually increases the craving for food in people who are obese.

"These people are actually hungrier than the rest of us. And they're hungrier because of the way they metabolize carbohydrates," said Taubes.

For Terri Hill, who weighed more than 200 pounds, success finally came with another low-carb diet — The Zone — based on a finely controlled balance of good carbs, good fats and lean protein.

"I felt that this worked better than any of the other diets I had tried. And I've been eating this balance [40 percent carbohydrates, 30 percent fats, and 30 percent proteins] now for four years. I lost 90 pounds of fat," Hill said. "Your blood sugar levels never go too high and never fall too low, but they fall in this nice moderate zone."

But are low-carb diets right for everyone? Experts agree, there's only one way to prove for certain that low-carb is better than low-fat, and that's with a long-term, randomized clinical trial.

Leading obesity researcher Dr. George Blackburn of Beth Israel Deaconess Hospital in Boston has funding from the Atkins Foundation for such a trial, which will compare a traditional low-fat diet with a modified Atkins diet that emphasizes good fats.

"We don't know whether he's right or not, but at least you know both the National Institutes of Health and the Atkins Foundation are interested in finding out," Blackburn said.

"In the meantime, there's plenty of compelling evidence to do the following," advised Johnson. "Get rid of the refined starches and sugars … eat more vegetables and fruit, eat lean protein and healthy fats. You'll lose weight and feel better and may reduce your risk for heart disease."

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