Gary Taubes, breaking down the nutrition myths....
Today marks my appearance on the Dr. Oz Show, which was, let’s just say, an interesting experience and leave it at that. It was the show, though, that (finally) prompted me to address an issue I’ve wanted to address for quite some time.
The Dr. Oz Show is one part health advice and discussion and quite a few parts entertainment, as Oz’s producers kept telling me in the days before we taped the episode. To make for what they consider good television they played me up as the second coming of Atkins – a persona that my wife likes to refer to as “meat boy” — while Oz got to play the role of the harvest king, extolling the healing virtues of fruits, vegetables and whole grains. This made it more difficult than I would have liked to get across the important messages from my books, but television is television and I certainly knew what they had in store for me.
My message and the message of Why We Get Fat was not that we should all be eating nothing but animal products – and certainly not the unappetizing meat and eggs that Oz’s crew prepared as props — but that carbohydrate-rich foods are inherently fattening, some more so than others, and that those of us predisposed to put on fat do so because of the carbs in the diet. That’s why I called the book Why We Get Fat rather than some variation on The Miracle 24-Hour (or 14-Day or Three Week or Three month) Diet Cure, which is more the norm for lay books in the nutrition genre.
The idea despite all the controversy is pretty simple. I’m arguing, as others have before me, that the same thing that makes our fat cells fat is what makes us fat — a fat person, after all, is a person with a lot of overstuffed fat cells — and what makes our fat cells fat is fundamentally the hormone insulin. Raise insulin levels and we accumulate more fat in our fat cells. Lower insulin and fat is released from the fat cells and the cells of our lean tissue can burn it for fuel.
There’s nothing particularly controversial about the science involved. If you doubt insulin regulates fat accumulation in fat cells, you can literally look it up in any good biochemistry or endocrinology (the study of hormones and related disorders) textbook – the latest editions, say, of Lehningers Principles of Biochemistry or Williams Textbook of Endocrinology, which are the authoritative texts in their respective fields. Look up the word adipocyte (the technical term for fat cell) and this is what you’ll find:
First Williams (and I’ll translate the technical terminology immediately after):
The activity of LPL within individual tissues is a key factor in partitioning triglycerides among different body tissues. Insulin influences this partitioning through its stimulation of LPL activity in adipose tissue. Insulin also promotes triglyceride storage in adipocytes through other mechanisms, including inhibition of lipolysis, stimulation of adipocyte differentiation and escalation of glucose uptake.
To understand what this means you have to know that LPL is the enzyme (in less technical language, the thing) that works to pull fat from the circulation into whatever cell it happens to be sitting on. If that cell is a muscle cell, the fat is used for fuel. If it’s a fat cell, the fat is stored. Triglycerides are the form that fat is stored in fat cells and transported through the blood stream in lipoproteins. Adipose tissue is fat tissue and adipocyte is the fat cell.
So what Williams says is that fat is stored in different tissues (partitioned) depending on how this enzyme LPL is distributed on the cells of those tissues, and its insulin that to a large extent determines this. Then it adds that insulin promotes fat storage through other mechanisms as well — it creates new fat cells (stimulation of adipocyte differentiation), and it inhibits the escape of fat from the fat cell and its use for fuel (lipolysis), and it also increases the uptake of blood sugar (glucose) into the fat cell, which might not be relevant but the authors of the textbook don’t apparently know this, and neither did I when I wrote Good Calories, Bad Calories.
Now here’s Lehningers Principles of Biochemistry:
High blood glucose elicits the release of insulin, which speeds the uptake of glucose by tissues and favors the storage of fuels as glycogen and triaglycerols, while inhibiting fatty acid mobilization in adipose tissue.
Lehningers uses the other spelling of triglyceride – triaglycerol – to denote the fat in the blood and in our fat cells, and we get high blood glucose by consuming carbohydrate rich foods, which end up as glucose (a carbohydrate) in our blood stream. We also tend to have high blood glucose when we have a condition called insulin resistance, which is the underlying defect in obesity, diabetes and heart disease. When Lehningers says insulin inhibits fatty acid mobilization that’s pretty much the equivalent of what Williams is saying about insulin inhibiting lipolysis.
The point of both is simple. Insulin puts fat in fat cells. That’s what it does. And our insulin levels, for the most part, are determined by the carb-content of our diet — the quantity and quality of the carbohydrates consumed. (Or if Jenny Brand Miller and her colleagues are right, also by our fat content — the lower the fat in the diet, the higher the insulin and vice verse.) The way to get fat out of fat cells and burn it, which is what we want to do with it, is to lower insulin. This has been known since the early 1960s.
One point I make in Why We Get Fat is that we all respond to this carbohydrate/insulin effect differently. Some of us can eat carbohydrate-rich meals and burn them off effortlessly. We’re the ones (like Oz) who partition the carbs we consume into energy. (This is the fuel gauge metaphor that I use in WWGF and that Oz’s producers reproduced wonderfully on the show.) And some of us partition the carbs we consume into fat for storage, and that partitioning depends on a lot of different enzymatic and hormonal factors — mostly relating to insulin and LPL as Williams Textbook of Endocrinology said).
There are a few obvious dietary means to reduce the amount of insulin we secrete and ultimately the level of insulin in our circulation day in and day out. One is to eat fewer carbohydrates; one is to improve the quality of the carbs we do eat, which means eating carbs that are less refined (their glycemic index is low or at least lower) and carbs that come with a lot of fiber attached (green leafy vegetables), and then eating less sugars, by which I mean both sucrose and high fructose corn syrup.
And this brings us to the point of controversy on the show – where Oz and I disagree. (Okay, one of the many points on which we disagree, but the one that needs clarification sooner rather than later). This is also the point that public health authorities, physicians and nutritionists almost religiously refuse to accept or even understand, because one implication of what I’m saying is that the good Dr. Atkins was right all along, and they just can’t get it through their head, as Oz can’t, that a diet of the kind Atkins recommended might be not only healthy but the medically appropriate treatment for the condition – in this case, obesity.
There are a couple of helpful ways to think about the role of carbohydrates in obesity and chronic disease, and one of them (the other I’ll discuss at the end of this post) is that some of us are more tolerant to the refined and easily digestible carbs and sugars in our diet than others. The more we can tolerate them the less we have to avoid them. Hence, the dose of carb-restriction that’s necessary to be lean and (probably) healthy is a small one. Again here’s how I put this issue of individual variation in WWGF:
…Multiple hormones and enzymes affect our fat accumulation, and insulin happens to be the one hormone that we can consciously control through our dietary choices. Minimizing the carbohydrates we consume and eliminating the sugars will lower our insulin levels as low as is safe, but it won’t necessarily undo the effects of other hormones—the restraining effect of estrogen that’s lost as women pass through menopause, for instance, or of testosterone as men age—and it might not ultimately reverse all the damage done by a lifetime of eating carbohydrate- and sugar-rich foods.
This means that there’s no one-size-fits-all prescription for the quantity of carbohydrates we can eat and still lose fat or remain lean. For some, staying lean or getting back to being lean might be a matter of merely avoiding sugars and eating the other carbohydrates in the diet, even the fattening ones, in moderation: pasta dinners once a week, say, instead of every other day. For others, moderation in carbohydrate consumption might not be sufficient, and far stricter adherence is necessary. And for some, weight will be lost only on a diet of virtually zero carbohydrates, and even this may not be sufficient to eliminate all our accumulated fat, or even most of it.
Oz and physicians like him think that there’s so much to be gained by eating whole grains and fruits (we agree on the green vegetables, although I do so less because of any compelling scientific evidence than because my mother insisted they were good for me) that they think this should be recommended to anyone and everyone and a diet that restricts them can’t possibly be healthful.
Oz implies on the show that everyone can benefit sufficiently by improving the quality of the carbs they eat and getting rid of the sugars, that any more significant restriction isn’t necessary. And he thinks any significant amount of carb restriction will cause problems because a) people won’t stay on such a restricted diet; b) they’ll replace these foods in their diet with high fat, high saturated fat meats and eggs and so increase their risk of heart disease (a point I discuss at length in both my books and is obviously critical), and c) they’ll develop diseases like cancer that Oz believes can be prevented by eating fruits and vegetables and maybe even whole grains.
As I point out on the show (or at least I did when the segment was taped, but it may or may not make it to the air as our taping session ran long), there’s precious little clinical trial evidence to support this last contention, but Oz and authorities like him believe in the healing power of fruits and vegetables, and they’re not all that bothered by the lack of clinical trials to support it.
This is the same take on the problem used by physicians and nutritionists who recommend low glycemic index diets instead of carbohydrate-restricted diets. They think this is enough to improve the quality of the carbs we consume, and the implicit assumption is that if we cut back on the quantity of carbs to any great extent we’ll either eat too much fat (or too much meat, period) or we won’t stick to the diet and any benefits will be lost.
What I’m arguing is that for many of us who run to fat, cutting down on the refined carbs and starchy carbs (potatoes, for instance) and on the added sugars will help, but it probably won’t help enough. The dose of carb-restriction won’t be sufficient to deal with the problem. We may stay fat. We may even get fatter. A blanket recommendation to eat fruits and vegetables and whole grains, as Oz prescribes and now Weight Watchers and the U.S. Dietary Guidelines, ignores this aspect of human variability completely. It assumes that people who are predisposed to fatten can tolerate the same foods and benefit from the same very mild dose of carb-restriction that the naturally lean can.
I don’t think that’s true. It’s that simple. I think that if we’re so predisposed to fatten that we’re already obese, we’re probably among those who have to restrict carbs far more severely – have a much greater dose of the intervention – to get even relatively lean, which means relatively healthy. So for some of us and maybe most of us, even fruit, the nutritionist’s darling of the early 21st century, can be fattening , and if it’s fattening, it means it’s probably causing far more problems than whatever antioxidants or phtyochemicals it contains may be preventing. (As even Wikipedia says, as of March 6th 2011 anyway, “While there is abundant scientific and government support for recommending diets rich in fruits and vegetables, there is only limited evidence that health benefits are due to specific phytochemicals.”)
The way I see it, Oz, who’s naturally skinny, can eat fruits and vegetables and whole grains to his hearts content and remain lean. For him, they can be the bulk of his diet and he can tolerate them and burn them off. They give him energy. They don’t make him fat. But most of his audience is not naturally lean, and they probably can’t. I’d argue that many of them have probably been living on diets very similar to the diet Oz is prescribing and it hasn’t helped them or certainly not to any significant degree. I get e-mails all the time now from people who tell me they were getting fatter and fatter on just those “heart healthy” diets.
Assuredly some proportion of the population and so Oz’s audience will lose a little weight eating as Oz recommends and getting rid of the refined grains and sugars in their diet, and they’ll be a little healthier for the effort. Getting rid of the sugars alone might make a significant difference on both counts. But it’s an insufficient dose of the intervention for a serious medical issue that typically requires far more. For those who are obese and want to be anything close to lean and stay that way, they’re likely to be better off getting rid of all the grains and much or most of the fruit, and then eating more of whatever foods they happen to eat or like that provide protein and fat – pulses, for instance, and tofu (a more complicated issue than I have time for here) for the vegetarians and vegans and animal products (meat, fish, fowl and eggs) for the rest.
This also speaks to a question I’ve been asked numerous times in e-mails from readers. Simply put, what about nuts and what about fruit? And here’s my answer: Nuts are not only Oz’s snack of choice, but the snack of choice of many low-carbers. And nuts and fruit are fine if your body can tolerate them. If you’re still heavier than you’d like, maybe it can’t. It’s a trade-off. If I eat fruit, other than maybe a handful of blueberries a day, I start to gain weight, so I don’t eat it. If I was fatter than I wanted to be — which I’m not — I’d consider giving up both the blueberries and the almonds I eat and see what happens. If it didn’t make any difference, I’d go back to them. If it did, I could decide how much I missed them and whether the trade-off of weight vs. fruits and nuts was worth it. You can look at any number of the nutrition websites to see which nuts have the lowest carb content and which fruits have the lowest sugar content and glycemic index and use that as a guide. But there’s no website or diet book that will tell you what your body can tolerate.
Finally, here’s the other way to look at carbohydrate-restricted diets, and it speaks to Oz’s belief that saturated fats are the cause of heart disease. As I explain in WWGF and did so on the Oz show, it’s almost assuredly the case that the same foods that make us fat are the same foods that cause heart disease and diabetes and cancer, etc. — the diseases that associate with obesity. These are the foods that were absent from human diets during the 2.5 million years of evolution leading up to the agricultural era, and so we’re still poorly adapted to dealing with these foods — easily digestible starches, refined carbs and sugars. When we remove these foods from our diets, we get healthier. Insulin levels come down and with them a host of metabolic disturbances normalize.
It was an email from my friend Bob Kaplan a few days before I taped the Oz show that reminded me of how best to phrase this argument. So I’m going to end with Bob’s e-mail because he said it as well or better than I ever could.
I was just thinking about the “beneficial effects” of a low-carb diet and how it’s essentially a misnomer.
When we eat low-carbohydrate diets, our “good” HDL tends to go up, our LDL becomes larger and fluffier (less atherogenic), our blood pressure goes down, and our triglycerides plummet. Does this mean a low-carbohydrate diet is beneficial to health?
Yes and no. While it appears “beneficial,” for me, it’s more of an indicator of our serum lipids “correcting” to levels that we are supposed to find in a healthy individual. In other words, if we look at a population of people who are chronically over-consuming sugar and refined carbohydrates, their serum lipids are going to be abnormal. When they go on a low-carbohydrate diet, they’re correcting the abnormality and the associated lipids will become more “favorable” (while I would argue that they’re just trending toward a normal, healthy human being) depending on which MD or researcher you ask.
So it is with weight “loss,” water “loss,” lipid and metabolic “benefits” of a low-carbohydrate diet. There is nothing magical about restricting carbohydrates, rather it’s closer to the kind of diet that we’ve been eating and are presumably genetically adapted to eat, and any loss of weight and water, any beneficial effects on serum lipids are just a correction rather than an improvement in health.
Benefits v. Correction:
A restricted-carbohydrate diet doesn’t make you lose weight; it corrects your weight.
A restricted-carbohydrate diet doesn’t make you lose water weight; it corrects your water weight.
A restricted-carbohydrate diet doesn’t improve serum lipids; it corrects serum lipids.
A restricted-carbohydrate diet doesn’t improve health; it corrects unhealthiness.