Monday, March 17, 2014
Diet, weight and health: confused only if you want to be!
The New York Times once again allocated some of its rarefied real estate to science writer Gary Taubes, who uses it to do what, in my opinion, he does best: ask the wrong question. His question is: why is nutrition so confusing? When my friend and fellow health crusader, Dr. Yoni Freedhoff, saw the column mentioned on Twitter, he responded with a tweet that said: “A pot yelling at the kettles.”
Before advancing my own harangue, I hasten to note that I know Mr. Taubes somewhat, and have nothing to say against him personally. To the best of my knowledge, he is well intentioned, hard-working, and intelligent. But with all the respect he is due, I, apparently like Dr. Freedhoff, find him quite misguided.
As a formally trained clinical researcher myself who has run a lab for nearly 20 years and published roughly 200 scientific papers, I can say without hesitation that our answers are only ever as good as our questions.
If, for instance, we ask: “Is there an association between Internet access and tuberculosis?” the answer would be yes. Where there is more Internet access, there is less TB. However, the association is meaningless. Internet access is simply a marker of higher living standards, which are in turn associated with many factors that protect against TB exposure. You can, I trust, come up with any number of such nonsensical associations yourself.
Equally important, and again I speak as someone whose career depends on doing clinical research, we don’t always need a randomized controlled trial (RCT), despite Mr. Taubes’ suggestion in today’s paper that we do. If, for instance, my foot were to catch on fire, I would not need a RCT to fetch a pail of water. We have no RCTs to “prove” that bullets through the chest are worse than corresponding “placebo bullets,” whatever those might be. We have no randomized trials proving it’s better to treat bullet holes through people with emergency surgery than it is to wait until the bleeding stops and see what happens.
I am by no means arguing against the importance of research. Again, unlike Mr. Taubes, I make my living doing it. But science is not a substitute for sense. Answers are only ever as good as questions, and thoughtful and honest analysis of data must look beyond the study hypothesis to what actually happened.
What do I mean by that last bit? Well, consider that the advice we got decades ago to cut dietary fat was never intended as advice to eat low-fat, high-starch, high-sugar cookies. When the advice to cut fat was first provided, there was no such thing as highly-processed, low-fat junk food. The food industry exploited the advice and invented low-fat junk food to take advantage of it. This issue of “unintended consequences” in dietary advice is enormously important, and I have addressed it at some length before. Rather than repeat all that history, I refer you to my prior column on the topic.
For now, let’s note the following. The advice to cut fat was intended to direct us to the naturally low-fat foods that existed at the time, namely vegetables, fruits, beans, lentils, whole grains, and lean meats. Does anyone doubt that if America ran mostly on such foods (rather than, as Madison Avenue seemingly now contends, donuts and coffee) our health would be much better? I do not.
We never followed the advice we got. Instead, the advice was distorted and, if I may be brutally honest, perverted. We started eating Snackwell cookies and, oh, by the way, never even reduced our fat intake! The National Health and Nutrition Examination Survey data at the time revealed this: the percentage of total calories from fat in the typical American diet went down not because we reduced our fat intake, but because we increased our total calorie intake, adding all of the newly tempting low-fat junk foods we allowed ourselves to believe we could eat limitlessly, and with impunity.
So, Mr. Taubes can act as if we asked, and answered a question about dietary fat intake and wound up confused. But is it confusing, surprising, or anything less than self-evident that continuing to eat about the same amount of fat while adding lots of refined starch, added sugar and calories would not advance our careers as icons of vitality or underwear models?
I would argue we are not, and were not confused, we are, and were conflicted. We were, and are, active participants in a massive collusion at the level of our culture. We wanted to have our low-fat cake and eat it, too. In other words: we probably really knew all along that “low fat” advice really meant eat more mixed greens, but we wanted it to mean: keep eating pastrami, and dilute the calories with low-fat cookies. And so we did. And here we are.
Which leads back to looking beyond the hypothesis. Studies that have looked at cutting fat by eating more naturally low-fat plant foods have, in fact, shown astonishing benefit, such as the reversal of coronary atherosclerosis, the prevention of heart attacks, and the favorable modification of gene expression. But that hypothesis was never tested at the population level. At the population level, we asked this: What will happen when Big Food takes advantage of the advice to reduce fat intake by inventing a whole new variety of junk food, and we all pretend that’s what we thought the advice meant all along, and eat a whole lot of that starchy, sugary junk and never actually reduce our fat intake either? I trust no one is too surprised with the answer: we will get fatter and sicker.
I am not out to argue for low-fat eating here. I have written extensively about “best diets,” including in 3 editions of an extensively referenced medical nutrition textbook and a review paper due out next month in Annual Review of Public Health. We can eat extremely well with low-fat intake or high-fat intake. We cannot eat extremely well, however, if our diets are comprised of glow-in-the-dark foods, whether low-fat, or sugar-free, or pick whatever version of lipstick on a pig you like.
Mr. Taubes is one of many New Age nutrition messiahs who have spawned a thriving cottage industry in iconoclastic messages. Since cutting fat was bad advice, we were told to cut carbs-by iconoclasts who saw the “flaws” in the low-fat message. But if cutting carbs was such a brilliant advance, where are all the thin and healthy people? We have since been told it’s not just carbs, it’s the glycemic index. It’s not just the glycemic index, it’s bad carbs and bad fats. It’s not carbs and fats, it’s wheat and gluten. It’s not just wheat and gluten, it’s all grains.
Mr. Taubes’ own particular preoccupation has been calories. He has contended they don’t count. This, too, is a topic I have addressed, repeatedly, and won’t belabor it here. I will simply note again that answers are only as good as the questions.
So, for instance: imagine a study in which calories are matched, but one diet is all highly nutritious food, and the other is all junk. If health, weight and body fat outcomes are worse on the junk food diet, doesn’t that prove a calorie isn’t a calorie?
Of course not! It simply proves that a jellybean is not a pinto bean. Was anyone actually in doubt about that?
We could run another study: two groups get diets of absolute junk, but one gets half the calories of the other. The group getting fewer calories has better health, weight, and body fat outcomes. Doesn’t this prove that only calories matter, and it doesn’t matter what foods they come from?
Of course not! Less junk may be slightly better than more junk, but it’s still junk. The study did not address critical questions: how would the junk food diets compare to diets of wholesome foods? How would junk food intake at varying calorie levels compare to “good” food intake at those same calorie levels?
Mr. Taubes and others like him, the iconoclasts out to save us from our confusion, worry the hell out of me. They can go on indefinitely under a veil of pseudo-erudition generating seemingly impressive answers to fatuous questions. If, for instance, Mr. Taubes is out to show us that he was right all along and calories don’t count, he will have no trouble designing a study to show exactly that.
Meanwhile, back in the real world: we are not confused, folks! A truly staggering volume of evidence shows that people who eat any diet conforming roughly to Michael Pollan’s famously pithy advice, “eat food, not too much, mostly plants,” and who exercise routinely are dramatically less prone to obesity and chronic disease than everyone else. We have watched a natural experiment play out at a scale unmatched by any clinical trial: as cultures have acquired affluence and started doing less physical work and eating more highly processed foods, they have joined us in the dark wood of modern epidemiology where obesity and chronic disease prevail. Those cultures that have held out against these trends, whether their diets are natively higher or lower in fat, inclusive or exclusive of animal foods, have enjoyed exceptional longevity and vitality.
I contend that if we are confused about diet and health, it’s the endless parade of self-proclaimed renegade geniuses perceiving the iconoclastic truth to which the rest of us mere mortals are blind who have made us so. But I go further and contend we are not confused at all.
We knew that “cut fat” meant eat more kale; we just pretended it didn’t. We knew that “cut carbs” was not a license to chow down on low-carb brownies, but we pretended otherwise. We know now that we can overeat gluten-free junk, or that America can turn to sugar-free, artificially sweetened donuts and eat 3 times as many, and get fatter and sicker still. We know that both the quantity and quality of calories matter, and that the importance of one does not obviate the relevance of the other.
We are not confused, we are conflicted. We want a magical formula for weight loss and health, rather than approaching these like any other worthwhile thing in our lives. Like any worthwhile thing that isn’t about one scapegoat or silver bullet, this isn’t about a terrific answer to a fatuous and irrelevant question.
We are not confused about the basic care and feeding of Homo sapiens, unless we choose to be.
David L. Katz, MD, FACP, MPH, FACPM, is an internationally renowned authority on nutrition, weight management, and the prevention of chronic disease, and an internationally recognized leader in integrative medicine and patient-centered care. He is a board certified specialist in both Internal Medicine, and Preventive Medicine/Public Health, and Associate Professor (adjunct) in Public Health Practice at the Yale University School of Medicine. He is the Director and founder (1998) of Yale University's Prevention Research Center; Director and founder of the Integrative Medicine Center at Griffin Hospital (2000) in Derby, Conn.; founder and president of the non-profit Turn the Tide Foundation; and formerly the Director of Medical Studies in Public Health at the Yale School of Medicine for eight years. This post originally appeared on his blog at The Huffington Post.
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