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Weighing In

Friday, October 19, 2007

A science journalist makes the case for low-carb diets.

Good Calories, Bad CaloriesGood Calories, Bad Calories
By Gary Taubes
Knopf, 601 pp., $27.95

Diet fads wax and wane, but for the past few decades, public-health experts have assured us there is a surefire path to weight loss: eat a diet that’s low in fat, cholesterol, and salt, and you will be less at risk for heart disease, diabetes, and cancer. But as Science magazine correspondent Gary Taubes asked in a 2002 New York Times Magazine cover story, “What if it’s all been a big fat lie?” That is, what if carbohydrates—specifically, refined carbohydrates and sugars—cause the diseases that plague modern Americans? What if they—not fat, cholesterol, or salt—are responsible for our obesity epidemic?

It was a fascinating thesis, albeit a controversial one. Now, five years after his groundbreaking Times piece, Taubes has come out with a new book, Good Calories, Bad Calories, which explores the topic at greater length. He has combed through every available study on heart disease, diet, and obesity—and arrived at some surprising conclusions.

“Obesity is not caused by eating too much,” Taubes writes, and “exercise is not a means of prevention.” Instead, “the fewer carbohydrates we consume, the leaner we will be.” The alleged preponderance of research that has supported low-fat diets is, in fact, “inadequate.” The field of public health “purports to be a science,” he says, and yet it “functions like a religion.”

Its prophets surely meant well. Taubes describes the story of how one charismatic researcher, Ancel Keys, so firmly believed that dietary fat was responsible for heart disease that he selectively published research confirming it. Keys won enough converts to his cause that other hypotheses seemed unlikely. Pretty soon, only research that promoted the dietary-fat hypothesis received funding and popular press attention. Once the hypothesis was “confirmed,” it started to sound like common sense.

The field of public health 'purports to be a science,' Taubes says, and yet it 'functions like a religion.'

All future studies were interpreted in light of the Keys theory. For instance, numerous studies showed that “primitive” people in Africa and the Pacific islands had low incidences of heart disease, cancer, and diabetes until they encountered the supposedly high-fat Western diet.

Of course, such research ignores the fact that those “primitive” tribal diets often featured little else but saturated fats. What they really lacked were refined carbohydrates and sugars. But since it seemed implausible to scientists that anything but dietary fats could cause the fat around our middles, and that anything but cholesterol could cause blockages in our arteries, public-health authorities rejected the carbohydrate thesis. Proponents of low-carb diets, such as the late Dr. Robert Atkins, were dismissed as quacks.

Today, Taubes notes, the best available medical research shows that low-fat diets will extend the human lifespan by no more than a few months. But it also shows that excessive sugar consumption throws the body’s regulatory systems out of whack, leading to fat accumulation, high blood pressure, cardiovascular problems, and insulin resistance. All of these symptoms are closely tied to obesity. If sugar is the villain, it makes perfect sense that obesity rates have increased even though Americans are now eating less fat and exercising more than ever.

Many Americans now accept this hypothesis. (The “Fat Free Foods” store by my apartment has been closed for three years.) In recent years, the National Institutes of Health has even funded studies of the Atkins diet—and found it to be more effective for weight loss than other diets. But Taubes seems not to have noticed the shift in public opinion. Indeed, the biggest problem with Good Calories, Bad Calories is that its author truly believes he is still an isolated heretic raging against the prevailing low-fat-diet religion. Since he fashions himself a lonely dissident—one without any medical credentials—Taubes documents his thesis meticulously. Unfortunately, he’s so meticulous that at times the book is unreadably weighty.

The other big problem is that Taubes wants Good Calories, Bad Calories to not only document the “big fat lie” of low-fat diets, but to be a rallying cry for good research. Too many researchers, he claims, approach questions with their desired conclusions already in mind. Taubes insists he is different. “I have spent five years on the research for and writing of this book,” he writes. “I tried to follow the facts wherever they led.” But Taubes received a $700,000 book deal to write about the “big fat lie.” One suspects that, much like the scientists he scorns, Taubes began his project with a preconceived conclusion.

That said, Good Calories, Bad Calories is the rare diet-and-nutrition book that isn’t trying to launch a thousand products. Anyone still preaching about the evils of fat will at least have to acknowledge Taubes’ work. Few books ever achieve that kind of influence.

Laura Vanderkam is a writer in New York City.

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