The Nightshirt Sightings, Portents, Forebodings, Suspicions

Good Calories, Bad Calories

One of the best books I read last year, Gary Taubes’ Good Calories, Bad Calories (hereafter, GCBC), is coming out in paperback next month. I’ll probably have to pick it up, because both of my hardback copies (!) are lent out to friends, and you know how that goes.

I can’t recommend this book enough. Despite the kind of dumb title, it’s not a diet book, but a piece of great investigative science journalism — as well as, in some ways, a history book. Specifically, it’s the history of how and why a particular meme — “fat is bad” — came to dominate nutritional thinking over the last half century. Taubes, a Science magazine reporter with a track record of debunking bad science and bad scientists, shows that it was personalities and politics, not sound science, that got the medical establishment and policymakers to scapegoat dietary fat. The evidence was never there, or was (and remains) extremely flawed: studies with inadequate controls, small sample sizes, often designed to find the thing the researchers were looking for. Yet when an idea becomes as widely touted and entrenched in the public consciousness as the “fat hypothesis,” it can have a snowball effect, biasing our perception and the direction of research thereafter. The meme stays in the picture.

If, like me, you grew up with the food pyramid, built on a broad base of grains and starches, it can be hard at first to wrap your head around Taubes’ conclusion that the real culprit in everything from heart disease to cancer is “wholesome” stuff like bread, pasta, cereal (and sugar) — not fat, not cholesterol, not salt. Atkins and South Beach and other “fad diets” have been vilifying refined carbs for decades, but they never get taken all that seriously. Even if you lose weight on those diets, replacing bagels and pasta with eggs, bacon, and steak is a recipe for a heart attack, runs the refrain. But study after study are showing that not to be the case. Evidence has been quietly accumulating for a long time that it’s carbs you need to cut out, and you can eat all the steak and eggs you want.

In retrospect it is easy to see why, as a meme, the fat hypotheses had such sticking power. It’s totally intuitive, for one thing: The fat you eat becomes the fat around your middle or butt. Why wouldn’t it? Taubes doesn’t spare the reader the complicated metabolic reasons why it doesn’t work that way (and it can make the book a bit of a slog at times): The main hormonal mediator between what you eat and what your body does with what you eat (for example, storing it as fat versus burning it for fuel) is insulin. Most people think of insulin as something that is just relevant for diabetics, but increasingly insulin resistance, the metabolic dysregulation characteristic of diabetes, is being seen as a model for numerous other health woes: obesity, heart disease, cancer, you name it. It just so happens that all these scourges coincided, in America and globally, with the expansion of insulin-spiking refined carbs in the diet (in bread, pasta, cereal, soft drinks, juices, etc.).

Try and persuade people of this, and you’ll see just how emotional people can get about their dietary beliefs. People look at you like you’re crazy if you defend fat and evil if you disparage bread — for all kinds of deep-rooted cultural reasons. Even once one accepts that one should cut out sugars and refined carbohydrates one still adds, under one’s breath or as an afterthought, “well, and eat low fat.” Probably because we’re so used to decades of austere, unrealistic, and even contradictory nutritional recommendations.

GCBC heralds a coming clarity in the field of nutrition. The dense science makes it slow-going at times, but it’s also the book’s greatest strength. With a wealth of evidence, it can’t be dismissed as another fad diet or crackpot opinion.

UPDATE (9/1/08):
My friend Josef Brandenburg, a DC personal trainer, has just published an excellent, easy-to-understand explanation of carbs, insulin, etc., and why it’s best to eat a low-carb diet. Read his article here.

About

I am a science writer and armchair Fortean based in Washington, DC. Write to me at eric.wargo [at] gmail.com.

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