Diet Detective: Gary, thanks for the interview opportunity. You have a very interesting background. You have master's degrees in engineering and journalism and you say that you became a science writer by default. Can you explain how that happened?

Gary Taubes:After reading All the President’s Men in college I wanted to be an investigative journalist, but I hadn’t worked for my high school or college newspapers. Despite that, I managed to get into Columbia Journalism School, but when I graduated, the only job I could get that allowed me to stay in New York City was as a fledgling science reporter at Discover magazine. So I became a science journalist, and within a couple of years I realized that there was a call for investigative journalism in science, just as there is in any other field. I’ve been hooked ever since.

Diet Detective:This whole diet controversy heated up in 2002 with an article you wrote for The New York Times Magazine. What was the genesis of that article?

Gary Taubes: I had actually pitched my editor at The New York Times Magazine a story on what had caused the obesity epidemic. At the time, our knowledge of the obesity epidemic was still relatively new, and the beginning of the epidemic could be localized in time to between two National Health and Nutrition Examination Surveys — between the late 1970s and early 1990s. I knew from my previous work for the journal Science that there were two fundamental changes during that period. One was the introduction of high–fructose corn syrup and its rise to prominence as the caloric sweetener of choice in the beverage industry. The other was the institutionalization of a low–fat, high–carb diet as a healthy diet that would not only prevent heart disease but also reduce our weight. Since the conventional wisdom as late as the 1960s was that carbohydrates make us fat, it was a likely possibility that telling an entire nation to eat carbohydrates was one reason we all got fatter. One thing led to another, and that second possibility turned out to be the one that best explained the data.

Diet Detective: In your first book, Good Calories, Bad Calories, and in your new book, Why We Get Fat: And What to Do About It, you explain how and why carbohydrates, not the number of calories we eat, make us fat. I know you’ve written whole books about this, but could you explain the reasoning in a nutshell (so to speak)?

Gary Taubes: The conventional wisdom both in the medical community and among the rest of us is that we get fat because we consume more calories than we expend. We overeat, in a word, or we’re too sedentary. And so it’s all about energy consumed and expended. But, as I describe in GC, BC and argue, forcefully, I hope, in Why We Get Fat, this calories–in/calories–out idea fails to explain some of the critical observations in the field. Men and women fatten differently, for instance. So they both have to be taking in more calories than they expend — that’s just the laws of thermodynamics, which always hold. But that fact tells us absolutely nothing about why the fat goes to different places on different sexes. Obesity and overweight have a strong genetic component — body types tend to run in families, not just hair and eye color and facial features. So the question becomes, what are these genes determining? How much we want to eat and exercise, or how much and where we store fat on our bodies? Prior to World War II, as I discuss in the book, European researchers and clinical investigators would define obesity not as a disorder of energy balance, as virtually everyone does today, but as a disorder of excess fat accumulation, which is the simplest possible thing you can say about the condition. And that leads you to ask the simple question, what regulates fat accumulation? The argument I’m making in the book, in a nutshell, is that obesity and overweight are disorders in the hormonal and enzymatic regulation of fat tissue. And since the amount of fat we accumulate is fundamentally regulated by the hormone insulin, the obvious culprits for why we get fat are the carbohydrates in our diet, because, for all intents and purposes, it’s carbs that regulate our insulin levels.

Diet Detective: Are these concepts similar to what Dr. Robert Atkins said more than 40 years ago? That is, we only store fat in the presence of insulin, and our body only makes insulin when blood sugar levels are rising, and all carbs (and only carbs) are metabolized as sugar. Therefore, if we don't eat carbs there won't be excess sugar in the blood, the body won't make insulin, and we won't store fat. What's the new news here? Also, where is this supported or not supported in the scientific literature?

Gary Taubes: My conclusions are very similar to what Atkins said. We both read much of the same research literature and so they are not, indeed, new. In fact, some of the ideas go back far beyond Atkins. The idea of the fattening carbohydrate dates to the early 19th century, at least. And I say this over and over in the book. One of my favorite sentences in the book is this one: “As I’ve suggested before, repeating myself on the subject of repetitiousness, very little that I’ve said so far is new.” The point is it’s almost assuredly right, but the medical community has been equating the Atkins diet with quackery and fad diets for so long that the hardest battle is convincing people to take these ideas seriously.

Indeed, one thing I don’t mention in the book but often do in my lectures is that in 1973, when a few close–minded physicians went after Atkins in a critique of ketogenic diets under the auspices of the American Medical Association, they took umbrage at Atkins’ speculation that there was some special fat–mobilizing hormone that was secreted on carb–restricted diets. In the process of doing so, they said “fat is mobilized when insulin secretion is diminished.” So they knew what it took to get fat out of the fat tissue and burn it for fuel — lower insulin levels — they just ignored it, despite the fact that this was the fundamental basis for Atkins’ argument. Today if you go to a biochemistry textbook (Lehninger’s, for instance, which is probably the most authoritative) or an endocrinology textbook (Williams Textbook of Endocrinology, for example, again the most authoritative), and look up “adipocyte,” which is the technical term for fat cell, in the index, you can then go to the appropriate page and it will tell you all the ways that insulin is responsible for putting fat into fat cells, when effectively every other hormone works to get it out. And all I’m saying is that the same thing that makes fat cells fat is what makes humans fat, since fat humans only come about because their individual fat cells accumulate too much fat. And what makes fat cells fat? Insulin. And what regulates insulin levels? The quantity and quality of carbohydrates we consume.

As for scientific evidence, the last decade has seen maybe a dozen studies comparing low–fat, low–calorie diets of the kind the American Heart Association prescribes to low–carbohydrate, eat–as–much–as–you–want, high–fat diets like Atkins’. In virtually every case — there may have been one exception — the Atkins diet produced at least as much weight loss, usually more, and greater improvement in heart disease risk factors. And this was despite the fact that the subjects on this diet could eat as many calories as they wanted and as much fat or even saturated fat as they wanted, and were actually encouraged to do so. It was these studies that first began to shift my beliefs, and they’re still being published, and they’re still finding the same thing.

Diet Detective: Other than the main point — that carbohydrates make us fat, — what’s the biggest surprise/shock you encountered in the scientific literature on weight control and during your research for your books?

Gary Taubes: Well, certainly this idea that calories–in/calories–out says nothing meaningful whatsoever about the cause of obesity. Even when I wrote my first book, Good Calories, Bad Calories, I still didn’t quite realize how meaningless this idea is and, as a result, how misguided and dangerous. And I believed it myself until I did this research. Just like everyone else, I thought that the way to lose weight, or at least maintain my weight, was to eat as little as I could and work out as much as I could. Now that I understand these issues, I’m still shocked and surprised that smart people can believe that a term like “overeating” or “overnutrition” has any meaning whatsoever. And when I interview researchers who do — I’m still just a working journalist after all — it usually takes me only about five minutes to get them to at least question these knee–jerk assumptions about what it means to say someone overeats.

Diet Detective Why are nutrition advocates so convinced that the calories–in/calories–out theory is the scientific explanation of why we're fat, and what’s so inherently wrong with that theory? Is it just that it is too simple? People who cut calories do lose weight, don't they?

Gary Taubes: They’re convinced because they never thought of it any other way. None of us did. And everybody they know thinks of it the same way. And it seems obvious. It’s as if we all grew up at a time when everyone thought the sun rotated around the Earth — I mean, it sure looks like that’s what it’s doing when we look up in the sky &mdsh; and so we never question it, and our friends never question it, because it just seems so obvious.

It’s not that this idea is too simple, though. It’s that it is literally meaningless. If someone gets fatter, if they gain weight, they have to take in more calories than they expend. That’s a given. That’s what the laws of thermodynamics tell us, but that’s all the laws of thermodynamics tell us. They say nothing about why someone gets fat or gets heavier or takes in more calories than they expend. Take boys and girls going through puberty. They start off, prepubescent, with roughly the same amount of body fat, and then they go through puberty and the boys lose fat and put on muscle while the girls put on fat in their breasts and hips, and they both take in more calories than they expend; they’re both growing, but what does the caloric imbalance have to do with whether they put on muscle or fat, or where, in the case of the girls, the fat goes? It’s all driven by hormones; growth hormones driving the growth itself, sex hormones determining whether it’s muscle they add or fat and where the fat goes. So the overeating thing, the calories–in being greater than calories–out, is an effect of the growth and the fat accumulation, not a cause. Their bodies are getting bigger, they’re adding bone and muscle and connective tissue and even fat, and so they need to bring in the necessary calories to fuel that growth, and the protein and fat necessary to supply the material required to build this new tissue and muscle, etc. And the point I’m making is that the same thing is almost assuredly true for overweight and obesity, as well. We don’t get fat because we overeat; we overeat because we’re getting fat. And the reason we get fat is because the carbohydrates we consume not only elevate insulin levels, but almost assuredly cause the condition known as insulin resistance, which works, in effect, to keep them elevated. We trap fat in our fat tissue — which is what insulin does — and we don’t burn it. Day in and day out, the effect of this “lipid trapping,” as researchers used to call it, is to make us ever fatter, In the 1980s, a brilliant French physiologist named Jacques Le Magnen said that it’s not a paradox to say that the reason people gain weight and become obese is because they are no longer able to lose weight. The insulin in their bloodstream keeps the fat locked in their fat tissue, and every day they add a little more.

Diet Detective: So are all carbohydrates bad? What about 100 percent whole grains? Have you done any additional research since writing Good Calories, Bad Calories? For instance, even the Atkins program has been modified, also the success of the South Beach Diet — meaning are there good carbs vs. bad carbs?

Gary Taubes: The reason I talk about carbohydrates in this context as being bad is because it’s the carbohydrates themselves, at a molecular level, that stimulate insulin secretion or cause insulin resistance, and it’s the insulin that then works to store calories away as fat. But when we go from the carbohydrates at this molecular level to carbohydrate—containing foods, then, no, of course, not all of them are bad. But the point I make in the book is this: the denser the carbohydrates in the food, the easier they are to digest, the quicker they hit the bloodstream, or the sweeter they are (which means the more fructose they contain), the more they ultimately raise insulin levels. So there are fattening carbohydrates or at least fattening carbohydrate–rich foods — the easily digestible or refined carbs and sugars — and there are non–fattening carbohydrate foods, like green leafy vegetables.

The catch is that someone who is profoundly obese, not just 10 or 20 pounds overweight, might be so sensitive to the carbohydrates in their diet that virtually any carbohydrate will work to keep them fat. We don’t know for sure, because the necessary clinical trials haven’t been done, but anecdotal evidence certainly suggests that this is true. So carbohydrates (or carbohydrate–rich foods) that are fine for a lean person or a moderately lean person — those that are what we might be tempted to call good carbs — may still be detrimental to someone who puts on a lot of weight easily.

As for the modified Atkins diet or South Beach, I’m not sure that those diets aren’t playing to the prevailing winds of what’s politically correct and aren’t doing so to the detriment of the diet or the dieter.

Diet Detective: What about fruits and vegetables — what if that's all we ate?

Gary Taubes: Well, we’re talking about two different things — fruits and vegetables — and the answer depends for both on the individual. If we’re naturally lean, then both are fine. No problem. As I say in Why We Get Fat, there’s nothing fattening about green leafy vegetables, because the carb content is low to begin with and the fiber content is high, so we digest those carbs slowly. Now, what about people who tend to fatten easily? People who are seriously obese, rather than just 10 or 20 pounds overweight? For these people, it’s trickier. The fatter you are, the more sensitive you are to the carbs in the diet. So it’s possible — unlikely, perhaps, but possible — that even the small amount of digestible carbs in green vegetables can be problematic for people like this. And for them, fruit can certainly be problematic because of both its carbohydrate content and its sugar content. I think the rush to foist off high–fruit diets on everyone in the country, including the obese and overweight, is a mistake. In that sense, I don’t believe in blanket prescriptions — what’s good for the naturally lean in this country may not be good for those predisposed to put on fat easily.

Diet Detective: Is all fat and protein healthy to consume? Should we be cautious of certain types of fat? Even if fat is not responsible for obesity, isn’t it still true that saturated and trans fats may cause disease?

Gary Taubes: Here I side with Michael Pollan. If you’re eating “food” instead of food–like substances, the fat it contains will be at the very least harmless and probably beneficial. I’ve probably spent as much time as anyone alive studying the literature on saturated fat and heart disease and its history — documented in Good Calories, Bad Calories — and the evidence that saturated fat causes heart disease or any disease is just terrible. In fact, the evidence is that saturated fats are harmless, if not beneficial, and that trying to avoid them is as likely as not to be as detrimental. I know this is a radical opinion, but study after study comes out saying that saturated fats are harmless — meta–analysis after meta–analysis — and the authorities just ignore them. And there’s good reason to believe it’s good for us.

As for trans fats, those aren’t going to be an issue if you’re eating real food. And the idea that animal protein is bad for us makes no sense whatsoever from an evolutionary perspective and is also not supported by the evidence. Among other things, in the 19th century, the healthiest and most vigorous populations on the planet — the Native Americans of the Great Plains, African pastoralists like the Maasai, and the Inuit — lived almost exclusively on animal products, although they were higher in fat than they were protein.

Now, are polyunsaturated fats somehow healthier than saturated fats, better for us, even if the saturated fats are harmless? That’s a different question, and I’m skeptical that it’s true. The one thing I can say for sure is that the kinds of clinical trials needed to establish that point beyond a reasonable doubt have never been done and probably won’t be, because of the expense.

Diet Detective: Based on what you say about eating carbohydrates, what are the foods we should or shouldn’t be eating in order to not get fat? In your recent blog posting Calories, fat or carbohydrates? Why diets work (when they do) you discuss "controlling variables in a scientific experiment" and how there may be several reasons for a dieter's success — it may not be simply that they were on a so–called "low–fat diet" or a vegan diet. Can you briefly explain?

Gary Taubes: The argument I make is that fat accumulation in the human body is tightly regulated by hormones and enzymes, and the hormone primarily responsible for increasing fat accumulation is insulin. So the more a carb–containing food raises insulin levels — either in the short term, like refined carbs or starches, or in the long term, like sugars — the more fattening it will be. And I argue that when diets work, they almost assuredly work because they either decrease the quantity of carbohydrates or improve the quality — that is, lower the glycemic index and remove the sugars — or both. And, as I point out in that blog post, this is probably true of all successful diets, including low&nash;fat, low–calorie diets. When I ask researchers who study adipose tissue (fat) metabolism if it is possible to decrease the amount of fat we carry in our fat tissue without lowering insulin levels, the answer is no. And the way we lower insulin through diet is by removing the fattening carbs — refined carbs, which means anything made from flour and other refined grains (rice, for instance), to starchy vegetables like potatoes, and sugars.

Diet Detective: How did so many scientists, researchers and public health advocates get this wrong? Or is it that science has got it right and it’s the nutritionists and public health advocates who haven’t followed what science has shown? Is that what you're saying?

Gary Taubes: No, the scientists (if you can use that word, and I argue in the epilogue of Good Calories, Bad Calories that it is not appropriate in this case) got it wrong first. Everyone else followed. They just bought into this idea that fat accumulation is all about energy balance, and not energy balance at the membrane of the fat cell, but energy balance at a full body level — what we eat and what we expend. And since they started with the wrong paradigm, everything they’ve done since has been misguided. This is one reason why you can find researchers doing the same experiments and making the same arguments in 2011 that they did in 1911. And because the field itself has no culture of skepticism, no culture of science, in effect, everyone sort of meekly goes along, never asking the key questions of some concepts that, if they thought about them critically for any length of time, they would realize are inherently foolish.

Diet Detective:Are there any scientific researchers who support your argument?

Gary Taubes: There are researchers who read my books and find the arguments compelling. Most will tell you that these ideas have to be tested, which they do. But they’ll also tell you that they’re more likely to be true than the conventional wisdom, which has been tested and has failed the tests. I’ve also stumbled upon a dozen researchers who have come upon these ideas on their own, although only one or two of them have made even the slightest effort to communicate these ideas to others in the medical literature.

Diet Detective: What's your take on exercise? Does it matter in terms of weight control? Does it matter at all? Can you also provide the evidence for your conclusions on this?

Gary Taubes: My take is that it has little or no effect on fat accumulation, and that lean people exercise because they’re lean; they don’t become lean by exercising. I do think it’s good for us, and it may even make us healthier in the short and the long run — although those assumptions could use some rigorous testing. I am a longtime jock myself and a devotee of no–pain–no–gain type gym workouts and hikes. But I just don’t think it makes a damn bit of difference when it comes to long–term fat accumulation. And this has been demonstrated time and again in clinical trials since the 1980s, and can be understood down to a molecular, enzymatic level, if anyone cares to look at the evidence. As I explain in my books, what exercise does is make you hungry. It doesn’t make you lean. Remember the concept of “working up an appetite?” Well, that’s what you do when you work out: You work up an appetite.

One caveat here, though. Every time I say publicly that I don’t think exercise has any meaningful effect on fat accumulation — and by exercise, in this context, I really mean increasing energy expenditure — my friends in the strength–training community reprimand me for what they think is compelling evidence that resistance training can induce fat loss, specifically in the context of low–carbohydrate diets. This may indeed be true, but I haven’t seen enough evidence personally to say it is. And even though I don’t believe it’s a lack of resistance training that causes us to get fat in the first place, it’s possible, and I’d like to avoid the usual e–mails from my friends, so I want to mention it here.

Diet Detective: In terms of what health advocates are now telling us, is salt the new fat? Can you explain?

Gary Taubes: I spent the better part of a year in the late 1990s reporting an article for Science on the evidence supporting the belief that salt causes hypertension. It was bad then, and it hasn’t gotten any better. As far as I can tell, it’s zealotry on the part of the anti–salt crowd and the results of one relatively recent trial — known as DASH Sodium — that are driving the argument that we should all eat less sodium. What I say in Good Calories, Bad Calories is relevant here. Consider the fact that obesity, diabetes, heart disease and gout are all hypertensive conditions, which means they are associated with hypertension. People with any of these disorders tend to be hypertensive, to have high blood pressure. Now, no serious researcher or clinician would argue that salt causes obesity or diabetes, and it certainly doesn’t cause gout. And what I argue is that Occam’s razor holds in nutrition and chronic disease just as it does in every science. Don’t reject a simple hypothesis until you have no choice. So let’s start by assuming that the same thing that raises blood pressure in an otherwise healthy individual is the thing that raises blood pressure in someone who is obese, or diabetic or gouty. What could that be? It turns out, and it’s been known since the 19th century, that carbohydrate–rich diets cause water retention and raise blood pressure. In fact, one supposedly negative side effect of carbohydrate–restricted diets like Atkins is that they can lower blood pressure so much that people on these diets have to add sodium back in. And it’s now known that one of the many things insulin does is raise blood pressure, through a couple of different mechanisms.

So maybe it’s the refined carbs and sugars that raise blood pressure and cause hypertension. That would fit with the epidemiologic evidence and even the clinical trials. The DASH diet, for instance, that was used in the DASH Sodium trial, is a diet very low in fructose — i.e., sugar (sucrose) or high–fructose corn syrup. And it’s arguably the case that it’s these sugars — fructose, in particular — that cause gout through their effect on uric acid. So I guess maybe salt is the new fat in the sense that the anti–fat movement was misconceived and the anti–salt movement probably is as well.

Diet Detective: What if you're mistaken, too? What about all the research showing that saturated fat may cause cancer — the China Study, for example? And the research showing that whole grains are good for the body? Was there any leap of faith in your interpretation of the scientific literature, or were you just reporting on evidence that should be perfectly clear and obvious to everyone?

Gary Taubes: Well, if I’m mistaken then I apologize. I do say in my books that this is a hypothesis that has to be tested, but I also say that the evidence — in my mind, at least — is sufficiently compelling that it should be treated as the null hypothesis. That is, the hypothesis that needs remarkable evidence to reject. As for the China Study, the study itself — not to be confused with Colin Campbell’s book by that title, which I will discuss shortly — is just a list of associations between hundreds of variables and health conditions in different counties in China. If you actually look at the raw data (page 106 of the massive academic publication on the data, Diet, Life-styles and Mortality in China, which I own), there is no association between animal protein and mortality from cancer. None. People who ate more animal protein did not have more cancer, or at least no more of them died from cancer than people who ate less. And it’s cancer that the Colin Campbell is concerned with in his book, The China Study.

In that book, Campbell massages the evidence through a series of steps until he can make the opposite claim. So he doesn’t tell you that animal protein is not associated with cancer in this study, but he says that blood markers of protein consumption are so associated, even though he gets this wrong as well. He never makes the claim, nor do any serious researchers anymore, that saturated fat causes cancer. Although it’s always been an open question whether poly–unsaturated fats do.

So, no, I tried my best not to take any leaps of faith. And I tried my best to be completely honest about what the evidence does and does not show. A scientific hypothesis, though, as Peter Medawar once put it, can be thought of as a story that you tell, and what you want to know is whether the story is consistent, and then, ideally, you want to do experiments to test it further. What I found in my research is that there is a consistent story that can be told from the observations of isolated populations eating their traditional diets in the 19th century through the latest science of heart disease, diabetes, obesity and even cancer and heart disease. Those populations that didn’t eat Western diets, which means, for the most part, that they didn’t have sugar or refined carbohydrates (white flour or white rice), had virtually no obesity, diabetes, heart disease or even cancer. And today that fact can be explained by the effect of sugars and refined and easily digestible carbohydrates on insulin levels, on insulin resistance, and all the negative sequelae that follow. Like any hypothesis, it may be wrong, but so far (and in my opinion) the data not only strongly support it but continue to get stronger with each passing year.

Indeed, I recently reported an article for Science on the mechanistic link that could explain why obesity and diabetes are associated with a higher risk of most cancers. And virtually everyone who studies this agrees that the link is insulin, or elevated levels of insulin known as hyperinsulinemia, and that insulin serves in a variety of ways to promote tumor growth and malignancy. I haven’t had time to write the story yet, and I won’t get into the dietary angle for Science because they prefer that I leave my own biases out of it, but two of the cancer researchers I interviewed — one at Harvard and one at Sloan–Kettering in New York — told me they fear that refined carbs and sugars are the primary or at least dietary cause of most human cancers. One of them said that refined carbs and sugars “scare him silly,” and the other said that he is effectively on the Atkins diet, not because he needs to lose weight, but because he doesn’t want to get cancer. I’m still trying to figure out what to do with this journalistically after I write the Science story, which I may not have time to do for another couple of months.

In no more than SIX words, what is your reaction to each of the following?

Diet Detective: Antioxidants?

Gary Taubes: More than six words, but: reactive oxygen species — the molecules we want antioxidants to fight — are created in large part by burning carbs (glucose) for fuel and so are a product of carb–rich diets. Eat fewer carbs and antioxidants in the diet become a moot issue.

Diet Detective: Artificial sweeteners?

Gary Taubes Better than sugar, but not ideal.

Diet Detective: Alcohol?

Gary Taubes: In moderation. Can be fattening.

Diet Detective: Weight lifting?

Gary Taubes: See earlier comment about resistance training.

Diet Detective: What’s always in your fridge and pantry?

Gary Taubes: Eggs, full–fat Greek yogurt, butter, almonds, coconut butter.

Diet Detective: What food would we never find in your fridge or pantry?

Gary Taubes: Well, I’m married, and we have two young children, and I don’t have my own pantry. I try not to be zealot about what my kids eat, although I try to keep their sugar intake to a minimum. And my wife has a mind of her own. Had I a pantry of my own, you would probably never find powdered sugar, soda, fruit juice or white bread in it or, for that matter, any product that proclaims itself to be low in fat.

Diet Detective: What do you generally eat for breakfast?

Gary Taubes: Scrambled eggs, bacon, Italian sausage.

Diet Detective: What’s your favorite “junk food?” (Meaning do you ever indulge in junky carbs?)

Gary Taubes: Chocolate, although typically the kind that’s at least 75 percent cocoa, which means it has minimal sugar.