Cochrane report on low-carb diets

The study on colon cancer and the so-called Western dietary pattern that I’ve been posting on lately (click here, here and here for the posts) is a travesty for a couple of reasons. First, it’s a travesty because it’s an observational study being passed off by its own authors (who should know better) as a study implying causality. The second reason it’s a travesty is because of the way the press has handled it. As I’ve posted previously both the New York Times and the Wall Street Journal – the two most prestigious papers in this country with the largest national circulation – both echoed the study’s author’s beliefs that red meat was the driving force behind the recurrence of colon cancer in the study subjects.

Why did the writers of these two major papers do this?

Because, as I explained in my post about the book Stumbling on Happiness, it fits with their belief system, so it was parroted without any critical evaluation whatsoever.

Let’s take a look at how the major media handled another study, one vastly more important than the colon cancer study, one that, were it reported properly, could make a vast impact on the health of millions. The major media dealt with this study by ignoring it. Why? Who knows, but probably because it didn’t fit into their notions of what the truth really is, so they responded to this incredibly important report by pretending that it doesn’t exist.

A few months ago the Cochrane Collaboration released a study showing that subjects on low-carb diets lost more weight and improved their cardiovascular risk profiles to a greater extent than did subjects following any other kind of diet. Did you read about this study in your local paper or see it on the evening news? I didn’t think so. I didn’t either.

Before we get into how and why this report is so important, let’s look at the significance of it as compared to the colon cancer study that has been avidly reported in all the major mainstream media.

The American Cancer Society estimates that there are going to be about 150,000 new cases of colon cancer diagnosed in the US in 2007 and that about 50,000 people will die of this disease this year. Based on a little back of the envelope-type calculation, these figures mean that probably somewhere in the neighborhood of 80,000-90,000 people will develop stage III colon cancer in 2007.

The colon cancer study that I’ve been posting about applies to these 80,000-90,000 people, which, though a lot of people, is a mere speck in terms of the US adult population. In fact, it represents way under one tenth of one percent. Yet an observational study that addresses a problem suffered by fewer than one tenth of one percent of adults makes big news. And an inaccurate, loaded study, at that.

How many people in the US are overweight and obese? According the the latest US government statistics something on the order of 66.3 percent of US adults are overweight and 32.3 percent are obese. The adult population of the United States is about 250 million, so applying these percentages tells us that 166,000,000 people are overweight and 80,000,000 people are obese (and these numbers are just adults – I didn’t calculate the number of kids who are obese). If we compare the number of obese people to the number of people who will develop stage III colon cancer this year, we find that for every person with stage III colon cancer there are 1000 people who are obese. And about 2000 who are overweight.

It’s difficult to determine the actual statistics showing the death rates from obesity because people don’t really die from obesity per se. They do die from obesity-related diseases, one of which is colon cancer. Heart disease, diabetes, multiple kinds of cancers, cirrhosis, gall bladder disease, and a host of others are all related to obesity. When a person dies from heart disease the death certificate says ‘heart disease’ not obesity even though the heart disease may well have been caused by or at the very least worsened by obesity. And it’s the same with the other diseases mentioned above. Although we don’t have the exact statistics on deaths caused by obesity, it’s pretty safe to say that the number is large; much, much larger, in fact, than the number of people who die from colon cancer, which, as I mentioned, is an obesity-related disease in many cases.

I’ve laid out these statistics so that you can put yourself in the place of the person who makes the decision as to what medical studies of the literally thousands that are published every month are worth and which will be reported in the mainstream media. Would you go for a poorly done, observational study that, at most, impacts 80,000-90,000 people or an extremely well-done study that impacts a thousand times that number?

Before we get to the actual study, let me tell you a little about the Cochrane Collaboration. In a previous post I discussed the weaknesses of meta-analysis studies. These are studies in which an investigator gathers together a number of studies, some of which may not even have reached statistical significance, and adds all the data from all the subjects together into one big meta-analysis study. The problem with these kinds of studies are numerous, but mainly arise because the people doing the study are the ones who decide which studies to include. Often these investigators have a conclusion in mind beforehand and go about looking for studies that confirm that conclusion and add them in while excluding those that don’t corroborate the conclusion.

I’m not the first person who has figured this out. Many people feel the same way I do about meta-analysis studies and pretty much write them off. In 1993 a group of 77 scientists from 11 different countries who decided to do something about the way that meta-analysis studies were done. They collaborated as a group called the Cochrane Collaboration, named after Archie Cochrane, a British epidemiologist, and derived a standardized methodology designed to minimize the influence of researcher bias in meta-analyses. The methodology used by the Cochrane Collaboration makes it virtually impossible for researchers to fiddle the data by the criteria they use to include or exclude studies. The Cochrane Collaboration publishes reviews of various scientific issues using their rigidly-controlled set of inclusion and exclusion criteria.

When you read a review published by the Cochrane Collaboration, you can be sure that it has been carefully controlled and that only studies meeting the groups standards make it into the analysis. For this reason, Cochrane Collaboration reviews are given a huge deal of credibility within the medical/scientific community. And, one would think, within the mainstream press.

The recently published review looks at low-glycemic index diets and low-glycemic load diets in comparison to all other weight-loss diets in terms of weight loss and cardiovascular risk factors. The Cochrane group plowed through 892 studies and came up with 68 that made their first cut. These 68 were intensively examined until only six were left that met the stringent Cochrane criteria.

Reasons for exclusion, among other things, included:

Articles were reviews, duplicate papers, the study had no control group or no randomisation, studies did not compare similar groups, the intervention was less than two weeks, weight loss was not the aim of the study, the trial endpoint was different in the two arms or the trial, the diets were both designed to be ‘weight maintaining’, or the participants were neither overweight nor obese.

Here is the rationale for the Cochrane Collaboration to do this review.

Our systematic review may clarify issues surrounding the role of low-glycaemic index or load diets in the management of obesity and overweight. If alterations in the glycaemic index or load of the diet alone can increase insulin sensitivity, decrease weight, or decrease poor health outcomes in obesity and overweight (including type 2 diabetes and its associated complications), then the use of low glycaemic index diets would have significant health and cost benefits for the community.

Indeed!

Since the strength of Cochrane Collaboration reports resides in the methodology used to include and exclude various studies, the largest part of the paper is spent in detailing why certain studies were and weren’t used. These discussions are probably not of much interest to most people reading this post, so I’m not going to dwell on them.

The summary of the study concluded that this review

indicates that weight loss was greater in overweight and obese people given low glycaemic index or load diets than in people given comparison diets, including higher glycaemic index or load diets and conventional weight loss diets. Similarly, loss of total fat mass and decrease in body mass index were significantly greater in the group receiving a low glycaemic index or load diet. The loss of 1-2 BMI units is clinically significant as is the weight loss observed with LDI [low-glycemic index and load] diets (up to 7 kg [15.4 lbs] during the intervention period). Improvements in the cardiovascular risk profile (indicated by a decrease in total cholesterol and LDL cholesterol) were significantly better with a low glycaemic or load diet than a comparison diet.

…low glycemic diets appear to be effective even in obese people who need to lose considerable amounts of weight. The added advantage of LGI diets are that they are simple to follow and they are more likely to result in satiety than other weight loss diets. Furthermore, provided people consume the right type of low GI foods, there is no need to limit the actual quantity of food to achieve weight loss. This is more conducive to good quality of life than a very restrictive diet.

And a tidbit plucked from the body of the report that I’m sure will interest readers of this blog:

Insulin resistance decreased in participants receiving an ad libitum reduced glycaemic load diet but not in the group receiving an energy-restricted, reduced-fat diet in the one study reporting this outcome. [Cochrane didn’t add this to the conclusion because only one of the six studies looked at this parameter.]

Finally, in their conclusion the authors of the review gave the following implications for practice (which are basically a rehash of the above statements, but I like to read them anyway):

Overweight or obese people on low glycaemic index diets lost more weight than those on high glycaemic index diets or conventional energy restricted weight loss diets, with the change in body mass, total fat mass and body mass index all significantly decreasing after the low glycaemic index diet compared to the comparison diet. It may be easier to adhere to a low glycaemic index diet than a conventional weight loss diet, since there is less need to restrict the intake of foods as long as low glycaemic index carbohydrate foods are predominantly consumed. In studies comparing ad libitum reduced glycaemic index or load diets to conventional restricted low fat diets, even though participants could eat as much as desired on the low glycaemic index or load diets, they fared as well, or better, in the outcomes than those on the comparison diet. Hence, lowering the glycaemic index of foods in the diet appears to be an effective method of losing weight, particularly for the obese.

To summarize: Low glycemic load diets – even those allowing unlimited foods – bring about more weight loss than any other conventional weight-loss diets. Low glycemic load diets reduce cholesterol and LDL better than any other weight-loss diets, including low-fat, calorically-restricted ones (i.e., the ones usually prescribed for elevated cholesterol and/or LDL). And low glycemic load diets are easier to stick with than conventional weight loss diets.

That about says it all.

I know all this and most readers of this blog know this, but the great unwashed masses don’t. The great unwashed masses, however, do know that red meat causes colon cancer. Or at least they think they do. Yeesh.

So, we have a review by what is generally considered the most reputable group around – a group with a methodology that defeats any ideological bias – reporting on a treatment that is applicable to over half of the US population, and this report is totally ignored by the media. If you search the New York Times, the Wall Street Journal and/or Reuters you will not find this study mentioned.

It boggles the mind to think that an observational study that applies to at most a tiny fraction of a percent of the population is written up everywhere while this review – applicable to at least 166,000,000 people – isn’t even mentioned. One would think that even that idiot Jane Brody, who is so desperate to lower her cholesterol and LDL, would have been all over this review. But only silence. I wonder why?

My additional commentary on the glycemic index.

Let me start out by saying that I hate the glycemic index (GI). It is the food-content equivalent to the BMI, which is nothing but height and weight wooled around in such a way as to make it look more scientific. In my opinion the only reason the GI was derived was that low-carb diets were proving so effective that they couldn’t really be ignored, yet the academic types couldn’t bring themselves to say a good word about low-carbohydrate diets, so they had to come up with some kind of code. They first thought they were onto something with the GI, but as it turned out, it was almost useless. Why? Because the GI was calculated on the most readily available subjects: healthy college students. Who knows what the GI is for a 57 year old woman with diabetes? Who knows what the GI is for a 62 year old man with metabolic syndrome? And, as calculated, the GI only works for individual foods. Let’s say you calculated the GI for a baked potato and calculate the GI for a quarter of a cup of sour cream, does that mean you can predict the GI for the potato and sour cream eaten together? Or what about if you eat the potato with sour cream, some green beans and a steak. Can you figure the GI for the whole thing? No, of course not. So what’s the use of the GI? No one eats single foods – virtually everyone eats mixed meals.

Another troubling concern about the GI is that fructose has a fairly low GI (about 17). So, adding fructose can reduce the GI of a food that it’s mixed with. For example, on a same weight basis a soft-drink has about the same glycemic index as does a potato, and though I’m not a fan of potatoes, for health reasons I would helluva lot rather eat a potato than drink the equivalent amount of Coke, though the GI would be about the same.

Once researchers realized that they couldn’t rely on the GI to get them the same results as a low-carb diet they decided to refine a little more. Why couldn’t they get the results? Because a lot of even low-GI foods can run your insulin up, and people were thinking they were doing good in selecting lentils over potatoes, then going face down in the baked beans because, afterall, they are a low GI food.

The academicians decided to go with the glycemic load concept, which is ever closer to a regular low-carbohydrate diet with the virtue being that it doesn’t have to be called a low-carbohydrate diet. To calculate the glycemic load you simply multiply the GI times the amount of the food containing that GI to get the glycemic load. It’s kind of like multiplying the amount of carbs in a food times the amount of the food to get the total carbs…except a lot more complicated.

It’s a whole lot easier to simply count the effective carbs (all foods with a lot few effective carbs have a low GI), which eliminates the fructose problem, doesn’t let you overeat on the low GI foods (which will run your insulin up), and gives whole groups of food that can be eaten with impunity. The only problem I see is that the pointy heads would have to call it a low-carb diet, and, well, that just wouldn’t do.

Incidentally, in the above Chochrane review, the study that did most of the heavy lifting in terms of outcome was the one using the glycemic load, which, as I said, is just about the same as a low-carb diet. My only quibble with the review is that I wish they had used studies with just low-carb diets.

Please note: I reserve the right to delete comments that are offensive or off-topic.

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15 thoughts on “Cochrane report on low-carb diets

  1. Bravo, another good one Dr. Mike. You’re really on a tear…..and we like it.

    Now if we could just convince the “great unwashed” to start taking their baths in something besides high fructose corn syrup……..hmmm.

    Best,

    W

  2. Great article as always, Dr. E! Not surprisingly, I haven’t heard of this study nor of the Cochrane Collaboration. It sounds like they do some pretty good work. It’s sad that so much of what people “know” is media driven. I’m not one to believe that liberals control the media anymore than I believe the conservatives control the media. There are a lot of both kinds of outlets out there, in about equal numbers, and every single one has an agenda. The agenda usually entails “what will get us the most viewers/readers?” I think they don’t report much on low-carb diets because the unwashed masses have written low-carb off as “extreme” and beyond that, they’d then have to actually DO something like give up their donuts. People would prefer to watch/read news that confirms their beliefs, so that is what the media outlets give them. People just aren’t going to stick around with an outlet that constantly says “You’re doing the wrong thing. Change your life if you’d like to live long and healthy.”

    Anywho, I’ll be posting a link to this at my blog tomorrow. Great stuff indeed! Thanks for your work in bringing truth to light.

    Scott Kustes
    Modern Forager

  3. I agree about the relative importance of the two meta-studies and I enjoyed your article. I only had one issue, that is how you discussed obesity. I look at obesity as a symptom rather than a cause of anything. About the only medical issue obesity actually causes, would be joint problems. Yes you can find correlation between obesity and a number of diseases, but only because they have the same cause (insulin resistance from eating too many carbs). I contend that you can be technically obese but still rather healthy from a cardiovascular perspective, although I admit that probably the majority of obese people have other IR related health issues.

    You’ve made a valid point and one that I, myself, make often in lectures. It used to be thought that obesity was the driving force behind heart disease, diabetes, high blood pressure, etc., but now is commonly considered a symptom – as are the others I mentioned – of underlying insulin resistance and hyperinsulinemia.

    Best–

    MRE

  4. One more thing. While I understnad the perils of mining data for these meta-studies, I don’t think it is unreasonable that they found an increased incidence of recurring cancer in those eating SAD. I just think they are wrong about which components of this diet are doing the damage. The inflammatory effects of carbs are probably at the root of the problem.

    At least I’d like to think that LC also has anti-cancer benefits. I’m sure it has cardiovascular benefits, and even if it had no effect on cancer it would still be the smart choice of diet.

    The low-carb diet has many anti-cancer benefits, the chief one being that it isn’t a cancer promoter as is the high-carb diet. I should post on this in more detail some time. Ah, so many posts needed, so little time.

    Cheers–

    MRE

  5. There are many low carbers who avoid saying they are. They are not embarassed, but tired of dealing with the negative comments!! Personally I love telling people, but few seem receptive to using it, even when they admit there is some good from it.

    Low carb is the best diet for at least the majority of people…but low carb “done right” with adequate, high quality fats and proteins! But getting the word out is what we need!! What can we do to get this info out to the media? What do we need to do to get their attention? I know a lot of people are expecting Gary Taubes’ book to make a difference, and I think it will….but will it be enough?

    I guess we’ll have to wait and see about Taubes’ book. I’m hopeful. It will be out in just a couple of weeks. I talked to him a few days ago, and he said that he had just gotten his own copies, which means the books are printed. Now it’s just a matter of getting them into the stores.

    Cheers–

    MRE

  6. Hi Dr. Eades,

    Have you ever written a post about body mass index? How did BMI become such an important number to so many people? I calculated my BMI here http://www.nhlbisupport.com/bmi/ and even if I reach my “goal” weight set by my MD I’m still going to be considered overweight. In your practice do you consider blood tests to be the gold standard on how well a diet is working?

    Thanks again,

    Dave

    Hi Dave–

    I don’t think I’ve written a post specifically about BMI although I have mentioned it a number of times. I suppose I should write one sometime just to blow off steam. The BMI is an idiotic way to determine anything.

    I would have to say that my gold standard for how a diet is working is the percent body fat. I like to see it go down. Even if weight stays the same (which it virtually never does), but the body fat percentage goes down, then, in my mind, the diet is a success.

    Cheers–

    MRE

  7. I read the link on Cholesterol. Thanks so much for that. I am not a doctor, as a matter of fact, I am a musician. I manage to talk about cholesterol everyday. I have asked people who are upset because their cholesterol is “high”. I have asked them what their numbers are and they do not know.I have asked people how cholesterol is used by the body…they do not know. I talk about cholesterol more than I do music. The longer that I consume a truly healthy diet, the more frustrated I get when someone tells me how unhealthy it is.

    I have also learned lots about the growth hormone and fasting since reading your blogs and have taken advantage of this knowledge. I think that it is quite strange that we are bombarded with bad information about healthy eating yet, obesity continues to be the fashion of the day? When will people figure out that something just ain’t right.

    Mary T.

    BTW, Since you live so close to Oprah, when is she going to have you on her show and get rid of that Oz guy. 😉

    I live right down the street from Oprah, yet I’ve never seen her. I’ve seen Stedman dozens of times; in fact, I played golf right behind him day before yesterday. Oprah has her pets, and I guess I’m not one of them.

    Cheers–

    MRE