Gary Taubes Challenges Conventional Wisdom on Diet, Weight Control and Disease
Posted by medconsumers on January 1, 2008
Good Calories, Bad Calories – Challenging the Conventional Wisdom on Diet, Weight Control, and Disease by Gary Taubes
If your doctor has ever told you to go on a low-fat diet, read this book. For 50 years the public has been told that dietary fat and excess calories are the cause of obesity, heart disease and other chronic illnesses. Journalist Gary Taubes, a correspondent for Science magazine, has spent years tracking down the scientific underpinnings for both assertions and found little to support them.
In “Good Calories, Bad Calories,” Taubes shows how the low-fat recommendation has steered Americans to higher consumption of refined carbohydrates, especially processed foods, sugar and white flour. It is the quantity and poor quality of the carbohydrates consumed today, he says, that are making us sick and overweight.
Initially, the low-fat guidelines were aimed solely at people who had suffered heart attacks. By the 1980s, the entire nation was advised to keep their cholesterol down and that meant a major reduction in saturated fats, which was, and still is, recommended to prevent heart disease. Taubes writes, “Though women were clearly meant to adhere to the low-fat guidelines, they had not been included in any of the clinical trials. The evidence suggested that high cholesterol in women is not associated with more heart disease, as it might be in men, with the possible exception of women under fifty, in whom heart disease is exceedingly rare.”
Taubes first presented his case against the low-fat diet in a 2001 Science magazine article entitled, “The Soft Science of Dietary Fat,” and one year later, in a New York Times Magazine article entitled, “What if it’s all been a Big Fat Lie?” With 115 pages of references and bibliography, his new book, “Good Calories, Bad Calories,” is clearly aimed at research scientists and physicians.
The book documents a big change that occurred in U.S. dietary recommendations. For well over a century, carbohydrates (white bread, potatoes, noodles, beer, etc.) were widely believed to be fattening. That conventional wisdom was displaced by the dietary fat/heart disease hypothesis promoted by two influential people of the 1950s.
One is Dr. Paul Dudley White, President Dwight D. Eisenhower’s cardiologist, who asserted that America’s heart disease epidemic began after World War II when the country started to eat more fat and red meat and less cereal and grains. The other is Ancel Keys, a University of Minnesota physiologist, who compared the diets of seven countries and found that those with high-fat intake also had a high rate of heart disease. He was also the first to promote the familiar message that dietary fat makes us fat.
Taubes found that the facts do not support the claims of these two early proponents of the low-fat diet. The American diet was high in fat and red meat prior to World War II, according to government food surveys. Drawing on the Bureau of Census records, Taubes argues that heart disease was not all that rare in the first half of the 20th century when better diagnostic technology became available (primarily the electrocardiogram).
By the 1950s, premature deaths from infectious disease and nutritional deficiencies were mostly eliminated, thereby moving heart disease up the list of common causes of death. And lastly, changes in classification of heart-disease deaths in 1965 account for the increase that began that year.
As for Keys’s study, the seven countries were selectively chosen to support his high-saturated fat/heart disease hypothesis. Had he randomly chosen France and Switzerland, for example, rather than Japan and Finland, Keys would likely have seen no heart-damaging effect from a diet high in saturated fat. (And Taubes wryly observes, there might be no such thing as the “French paradox,” referring to the country’s storied high intake of saturated fat and comparatively low rate of heart disease.) This criticism was leveled at Keys’s work when it was first published. Still the American Heart Association eventually approved his low-saturated fat hypothesis as if it were backed by strong evidence and word went out to the public at large when Keys made the cover of Time magazine in 1961.
The fat-restriction recommendation has been kept alive in the last three decades by a small, select group of obesity researchers with university affiliations. The most striking fact about the evolution of the low-fat diet consensus, says Taubes, is that it has been tested in only two trials—on a few hundred middle-aged men who had already suffered a heart attack. Results of these trials were contradictory. The diets tested thereafter were cholesterol-lowering diets that replaced saturated fats with unsaturated fats.
Big Test Fails
By the 1970s, the National Heart, Lung, and Blood Institute decided it was time to test the low-fat, low-cholesterol diet hypothesis with a large, expensive trial. The MRFIT, or the Multiple Risk Factor Intervention Trial, randomly assigned 12,000 men either to a treatment group or a control group. All were healthy middle-aged American men with cholesterol so high (over 290 mg/ml) they were thought to be at imminent risk of heart attack.
The men assigned to the treatment group were counseled to quit smoking, take drugs to lower high blood pressure and eat a low-fat, low-cholesterol diet. They were told to substitute margarine for butter; eat no more than two eggs a week, drink skim milk; and avoid red meat, cakes, puddings, and pastries. The men assigned to the control group were left to their own devices about eating and seeking medical care. All were followed for seven years.
When MRFIT was published in 1982, the disappointing results were summarized nicely in one Wall Street Journal headline, “Heart Attacks: A Test Collapses.” Though slightly more deaths occurred in the treatment group, Taubes shows how heart disease researchers did not let go of the dietary fat/heart disease hypothesis, even when proven wrong. In a subsequent large U.S. trial, all the participants were instructed to go on a cholesterol-lowering diet because it was considered unethical not to. Cholesterol-lowering drugs became the distinguishing feature of the treatment groups in subsequent trials.
While researchers continued to explore the idea that restricting dietary fat reduces the risk of premature death in population studies, some found that the opposite was true. The 1985 Honolulu Heart Program, for example, found that high-fat diets are significantly associated with a lower risk of total mortality, cancer mortality and stroke mortality. Questionnaires filed periodically by participants of another study called the Nurses Health Study showed that the less fat consumed, the more likely they would get breast cancer.
Finally, in 2001, the Cochrane Collaboration sought to answer the low-fat diet question once and for all when it published a systematic review of the world’s best quality trials that had randomly assigned healthy adults to go on a “reduced or modified dietary fat” diet or continue eating as usual. The 27 trials that met the predetermined high-quality criteria had a combined total of about 10,000 participants. The trials lasted an average of three years. The Cochrane reviewers found that the low-fat or cholesterol-lowering diets had no effect on longevity and “no significant effect on cardiovascular events.”
The topic of weight control takes up about half the book. Though weight loss has long been promoted as the additional advantage of going on a low-fat diet, studies failed to prove this purported benefit as well. A 2002 Cochrane review of all relevant clinical trials (28 in all) concluded, “Low-fat diets induced no more weight loss than calorie-restricted diets, and in both cases the weight loss achieved was so small as to be clinically insignificant.” Conversely, Taubes cites trials showing that the high-fat diet, most notably the Atkins diet, results in more weight loss.
Total immersion in the last two centuries’ worth of research has convinced Taubes that dietary fat, including saturated fat, is not a cause of obesity, heart disease or any other chronic disease of civilization. Instead: “Through their direct effect on insulin and blood sugar, refined carbohydrates, starches and sugars are the dietary causes of heart disease and diabetes. They are the most likely dietary causes of cancer, Alzheimer’s disease and other chronic disease of civilization.” And contrary to conventional wisdom, obesity is not a disorder of overeating. Rather it is a disorder of fat accumulation due to too much insulin. (See related interview below.) What’s more, Taubes concludes that exercise is highly overrated as a means of weight control.
Taubes found enough evidence to warrant a clinical trial that tests his carbohydrates-make-you-fat-and-sick hypothesis. But he has no faith in the carbohydrate-restricted diet trials planned by the U.S. National Institutes of Health and the Dr. Robert C. Atkins Foundation because they will include only obese or overweight participants and are designed to test only weight loss.
What Taubes would like instead is a trial with healthy lean and normal-weight participants followed long enough to see whether an excess of refined carbohydrates will make them fat and develop chronic diseases. Another suggested trial would include a spectrum of participants—lean to obese—including many who have metabolic syndrome and/or type 2 diabetes.
Trials like these are not likely to take place—at least not in the near future—because a carbohydrate-restricted diet is by definition a fat-rich diet, and the medical community has been telling the public for the last half century that such a diet is dangerous. In the meantime, read this book and make up your own mind about which hypothesis has the most merit.
Maryann Napoli, Center for Medical Consumers © January 2008