Monday, March 15, 2010

Check It Out: Good Calories, Bad Calories

If the members of the American medical establishment were to have a collective find-yourself-standing-naked-in-Times-Square-type nightmare, this might be it. They spend 30 years ridiculing Robert Atkins, author of the phenomenally-best-selling ''Dr. Atkins' Diet Revolution'' and ''Dr. Atkins' New Diet Revolution,'' accusing the Manhattan doctor of quackery and fraud, only to discover that the unrepentant Atkins was right all along. Or maybe it's this: they find that their very own dietary recommendations -- eat less fat and more carbohydrates -- are the cause of the rampaging epidemic of obesity in America. Or, just possibly this: they find out both of the above are true.
So begins Gary Taubes' thought-provoking and spectacularly polarizing July 2002 cover article for the New York Times Magazine entitled "What If It's All Been a Big Fat Lie?" Taubes, an award-winning science journalist, points out that well into the 1970s, the scientific consensus was that diets high in "sugars and starches" -- in other words, carbs -- caused obesity. Up until that point, "the accepted wisdom was that fat and protein protected against overeating by making you sated, and that carbohydrates made you fat." Thirty years ago,
you could still find articles in the journals describing high rates of obesity in Africa and the Caribbean where diets contained almost exclusively carbohydrates. The common thinking, wrote a former director of the Nutrition Division of the United Nations, was that the ideal diet, one that prevented obesity, snacking and excessive sugar consumption, was a diet ''with plenty of eggs, beef, mutton, chicken, butter and well-cooked vegetables.'' This was the identical prescription Brillat-Savarin put forth in 1825.
But over the past three decades, "we've been told with almost religious certainty by everyone from the surgeon general on down, and we have come to believe with almost religious certainty, that obesity is caused by the excessive consumption of fat, and that if we eat less fat we will lose weight and live longer."

What explains the shift in conventional wisdom? In 1977, "a Senate committee led by George McGovern published its 'Dietary Goals for the United States,' advising that Americans significantly curb their fat intake to abate an epidemic of 'killer diseases' supposedly sweeping the country," and "peaked in late 1984, when the National Institutes of Health officially recommended that all Americans over the age of 2 eat less fat." But according to Taubes, the reported increase in heart diseases that triggered these conclusions was wrong, and there was (is) no evidence to support the hypothesis that consumption of meat and dairy products had led to a dramatic uptick in heart disease. In the 1980s, the N.I.H. spent hundreds of millions of dollars trying -- and failing -- to link fatty diets with heart disease, but on a "leap of faith," posited nonetheless that the link existed. And "once the N.I.H. signed off on the low-fat doctrine, societal forces took over":
The food industry quickly began producing thousands of reduced-fat food products to meet the new recommendations. Fat was removed from foods like cookies, chips and yogurt. The problem was, it had to be replaced with something as tasty and pleasurable to the palate, which meant some form of sugar, often high-fructose corn syrup. Meanwhile, an entire industry emerged to create fat substitutes, of which Procter & Gamble's olestra was first. And because these reduced-fat meats, cheeses, snacks and cookies had to compete with a few hundred thousand other food products marketed in America, the industry dedicated considerable advertising effort to reinforcing the less-fat-is-good-health message. Helping the cause was what Walter Willett calls the ''huge forces'' of dietitians, health organizations, consumer groups, health reporters and even cookbook writers, all well-intended missionaries of healthful eating.
The message was loud and clear: Go low-fat. Eat carbs instead. For decades, this mantra was pounded into our heads by academics, health professionals, agribusiness and marketers alike. But these days, it's become widely accepted that carbs spike insulin production, which in turns triggers weight gain. And "[f]ew experts now deny that the low-fat message is radically oversimplified."
If nothing else, it effectively ignores the fact that unsaturated fats, like olive oil, are relatively good for you: they tend to elevate your good cholesterol, high-density lipoprotein (H.D.L.), and lower your bad cholesterol, low-density lipoprotein (L.D.L.), at least in comparison to the effect of carbohydrates. While higher L.D.L. raises your heart-disease risk, higher H.D.L. reduces it...
But it gets even weirder than that. Foods considered more or less deadly under the low-fat dogma turn out to be comparatively benign if you actually look at their fat content. More than two-thirds of the fat in a porterhouse steak, for instance, will definitively improve your cholesterol profile (at least in comparison with the baked potato next to it); it's true that the remainder will raise your L.D.L., the bad stuff, but it will also boost your H.D.L. The same is true for lard. If you work out the numbers, you come to the surreal conclusion that you can eat lard straight from the can and conceivably reduce your risk of heart disease.

I'm not saying you should immediately run screaming from carbs and start stocking up on lard. But it's worth checking out Taubes' claims for yourself.

I've just begun reading Taube's 2007 book, Good Calories, Bad Calories, and will post a review when I'm done. So far, I'm finding it an engaging read. If nothing else, it encourages intellectual curiosity: Taubes challenges readers to look askance at conventional wisdom and to question whether there's evidence to support what many of us have been taught about diet and nutrition. A healthy dose of skepticism is always a good thing. (It certainly helped color my reading of the New York Times' recent article on the "obesity-hunger paradox.")

Just like his controversial New York Times Magazine article, the talking heads are split on Taube's book. (Michael Pollan and Andrew Weil are fans; Jillian Michaels and Mehmet Oz are not.) And not all reviewers agree with Taube's conclusions. But regardless of where you land on this issue, there's certainly a lot of food for thought here.

After the jump: Video of Taube's 2007 lecture at U.C. Berkeley (in case you don't feel like reading his 468-page book, but want to get the gist of what he's saying).