A couple of months ago I posted several times on an Israeli study published in the New England Journal of Medicine (full-text here) showing that low-carb diets brought about more weight loss and better lipid profiles than low-fat diets.   (See the various posts here, here and here)   Based upon how the press reported this study,   I figured that it would drift into the haze of history and never be mentioned again.   After all, this wasn’t a particularly good study – there are many others better done that show an even greater effect.   And they were all forgotten.   None made any impact on the mainstream docs.   Why should this one be different?

Imagine my surprise today when I got my emailed weekly version of Medscape Internal Medicine and found not just a lukewarm recommendation for the low-carb diet, but an enthusiastic one.

Medscape is a subscription service available only to physicians and is as mainstream as it gets. The lead article in this weeks issue is not really an article, but a video lecture.   One Dr. Sandra Fryhofer lectures the mainstream docs subscribing to Medscape on what the above study shows.   She points out the weaknesses of the low-fat diet and is positively enthusiastic about the low-carb diet.   She does issue a disclaimer, i.e., that the study was partially funded by the Atkins Foundation, but that’s about all.

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I’m always amazed at the number of comments this blog gets from readers who are worried about discussing health issues with their doctors.  Most are a variant of this composite of many comments I’ve read:

I’ve been on a low-carb diet, and I’m afraid my cholesterol is going to be up a little and my doctor will want to put me on a statin.  How can I show him/her that I’m really on the right track?

Another common variant:

I want to go on a low-carb diet, but I’m sure my doctor will be against it.  What should I tell him/her?

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During my Monday morning troll of the medical literature I came across a paper in Nutrition Research showing that a semi-sort-of low-carb diet improves lipid profiles significantly better than does a low-fat diet.

The researchers who performed this study are a tad more enlightened that the normal run-of-the-mill lot we typically find doing this sort of work in that these folks looked at the lipid parameters most likely to be valid, if the lipid hypothesis is ever proven: triglycerides, HDL-cholesterol (HDL), and the number of small, dense LDL-cholesterol (LDL) particles.

Before we get into the study results, I want to take a bit to go over the problems that bedevil anyone trying to study diet. Macronutrients – fat, protein and carbohydrate – exert numerous effects on metabolism. And so do calories. The problem is in determining which of these variables causes the effect in question. If we place two groups of subjects on differing diets, one on a low-carb, high-fat diet and the other on a low-fat, high-carb diet, and we keep the calories the same in both groups, and we find that those subjects on the low-carb diet reduce their triglycerides, what does that tell us. Most of us will conclude that the reduction in carbs brought about the effect. But did it? It could just as easily have been the increase in fat.

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John Tierney, science blogger for the New York Times, was as taken aback by the abject stupidity hostility of the comments to his recent post on fat in the diet that included a response from Gary Taubes about the Israeli low-carb study as I was in my recent post about his post. He decided to post on the subject again, specifically addressing the comments quibbling with the findings on saturated fat. And he included more feedback from Gary.

What we have to keep in mind here is that nutrition is a science (or at least should be) and science is about generating hypotheses, making predictions from our hypotheses, and then seeing if they hold true. The relevant hypothesis here — i.e., what we’ve believed for the past 30-odd years — is that saturated fat causes heart disease by elevating either total cholesterol or LDL cholesterol, specifically. So our prediction is that the diet with the higher saturated fat content will have a relatively deleterious effect on cholesterol. We do the test; we repeat it a half dozen times in different populations. Each time it fails to confirm our prediction. So maybe the hypothesis is wrong. That seems like a reasonable conclusion. No one is proving anything here — as some of your respondents like to decry — we’re just looking at the evidence and trying to decide which hypotheses it supports and which it tends to refute.

The knee-jerk response — as exemplified by quite a few respondents — is to assume that sometime in the not-too-distant past, maybe the 1960s or 1970s, before this low-fat dogma set in, such trials, or far better trials, were done and found the opposite — that the higher the saturated fat in the diet, the lower the cholesterol and the better the cholesterol profile. Or the higher the saturated fat, the greater the mortality. But that’s simply not the case, as I point out in my book. In fact, I’ve been criticized (by Gina Kolata, among others) for going on and on in the book about all the different studies. But I did so precisely because I didn’t want to be accused of cherry picking the data. (I was anyway, but that’s just the nature of this business.) When Ancel Keys, for instance, reported in the 1950s reported that saturated fats raised total cholesterol, which they did in his studies, he based it on comparisons of butter fat to polyunsaturated oils in studies that lasted only two to nine weeks. (He also reported, curiously enough, that the saturated fats had no significant effect on LDL.)

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