Thursday, July 17, 2008

Two Year Dietary Trial Results: Low-Carb Better than Low-Fat

The study just published in the New England Journal of Medicine, Weight Loss with a Low-Carbohydrate, Mediterranean, or Low-Fat Diet (free full-text), is quite a read, with lots of data and lots of findings to explore and look at!

First things first - the objective of the study was to compare the effectiveness and safety of weight loss diets over a two year period.

The dietary approaches included in the study:
  • a low-carb diet, loosely based upon the Atkins diet, no calorie restriction
  • a Mediterranean diet, calorie restricted, based on the recommendations of Dr. Willett & Dr. Skerrett (Eat, Drink & Be Healthy)
  • a low-fat diet, calorie restricted, based on the American Heart Association guidelines

In addition to weighing participants each month and measuring waist circumference, the researchers measured at reporting invervals (6-months, 12-months and 24-months) total cholesterol, LDL, HDL, triglycerides, fasting blood glucose, fasting insulin, HbA1C, blood pressure, HOMA-IR, C-reactive protein, leptin, adiponectin, bilirubin, alkaline phosphatase, alanine aminotransferase and urinary ketones.

Enrolled in the study were 322 volunteers; they were provided their largest meal each day (lunch) at work, and given support and guideance about their diet throughout the study period. Of the 322 who started the trial, 95.4% completed one year, and 84.6% (272 participants) completed the 24-months - making this perhaps, the best adherence level in a dietary trial lasting two years!

So what happened? Let's look at the various outcome measures to see.

Weight Loss

The mean weight changes among the 272 participants who completed 24 months of intervention were:

–3.3 ±4.1 kg in the low-fat group (7.3-pounds)
–4.6 ±6.0 kg in the Mediterranean-diet group (10.1-pounds)
–5.5 ±7.0 kg in the low-carbohydrate group (12.1-pounds)

Overall, in the intent to treat data (which includes even those subjects that did not complete the study) the weight loss was reported as:

–2.9 ±4.2 kg for the low-fat group (6.4-pounds)
–4.4 ±6.0 kg for the Mediterranean-diet group (9.7-pounds)
–4.7 ±6.5 kg for the low-carbohydrate group (10.3-pounds)

The reason I note the two findings is that in the media reports, the trend appears they're reporting the intent-to-treat numbers, which are lower because they include the 50 subjects that dropped out. Those who actually completed the study are the data I prefer to look at for weight loss since it accurately presents how effective the dietary approaches are when continued for two years!

Waist Circumference

-2.8 ±4.3 cm in the low-fat group
-3.5 ±5.1 cm in the Mediterranean-diet group
-3.8 ±5.2 cm in the low-carbohydrate group

Lipid Profiles

The graph itself speaks volumes:

High-Sensitivity C-Reactive Protein, High-Molecular-Weight Adiponectin, and Leptin

The level of high-sensitivity C-reactive protein decreased significantly only in the Mediterranean-diet group (21%) and the low-carbohydrate group (29%), during both the weight-loss and the maintenance phases, with no significant differences among the groups in the amount of decrease.

During both the weight-loss and the maintenance phases, the level of high-molecular-weight adiponectin increased significantly in all diet groups, with no significant differences among the groups in the amount of increase.

Circulating leptin, which reflects body-fat mass, decreased significantly in all diet groups, with no significant differences among the groups in the amount of decrease; the decrease in leptin paralleled the decrease in body weight during the two phases.

Fasting Plasma Glucose, HOMA-IR, and Glycated Hemoglobin

Among the 36 participants with diabetes, only those in the Mediterranean-diet group had a decrease in fasting plasma glucose levels (32.8 mg per deciliter); this change was significantly different from the increase in plasma glucose levels among participants with diabetes in the low-fat group.

This is critically important to note - the low-fat group experienced a rise in fasting blood glucose over the course of the two years; this despite a greater calorie deficit than the other two diets, and a greater increase in physical activity! Yet, this type of diet is exactly how the ADA recommends people at risk for or diagnosed with diabetes eat, while expecting ever increasing doses of medication to cover their progressive decline in glycemic control.

It is also noteworthy that, "there was no significant change in plasma glucose level among the participants without diabetes." Basically those who did not have diabetes did not experience any change in their values over the period of the study.

What the researchers did not note in their written text of the results was this - the low-carb dieters had similar declines in their fasting blood glucose levels through month 12, followed by a progressive decline through month 24.

If we look at the data provided, we can see something important changed - the quality of the carbohydrate they consumed seems to have declined. If you look at the table providing details of the dietary intakes, one major change in the low-carb group between moth 12 and month 24 pops out - as the study progressed, the consumed less and less fiber on average, compared with their baseline intake. Now early on, that's to be expected. Later, as carbohydrate is increased - if quality whole foods are the choice - fiber typically increases!

In contrast, insulin levels decreased significantly in participants with diabetes and in those without diabetes in all diet groups, with no significant differences among groups in the amount of decrease.

Among the participants with diabetes, the decrease in HOMA-IR at 24 months was significantly greater in those assigned to the Mediterranean diet than in those assigned to the low-fat diet.

Again, in the text, the researchers do not note if there were changes in HOMA-IR in the low-carb group. There was - over the 24-month period, the HOMA-IR in those with diabetes, following the low-carb diet, declined by 1.0; in those with diabetes following the low-fat diet the decline was 0.3; and in those with diabetes following the Mediterranean diet the decline was 2.3.

The last item reported in the section was the HbA1C levels. Among the participants with diabetes, the proportion of glycated hemoglobin at 24 months decreased by:

0.4 ±1.3% in the low-fat group
0.5 ±1.1% in the Mediterranean-diet group
0.9 ±0.8% in the low-carbohydrate group

The changes were significant only in the low-carbohydrate group.

The lower HbA1C is perhaps one of the most important outcomes of this study. The diabetics, in the low-carb group, were able to lower their levels by 0.9 over the 24 months and this was significantly greater than those in the two other diets. Unfortunately the researchers did not include the baseline HbA1C for participants, so we do not know what the reduction really means.


Tests Changes in bilirubin, alkaline phosphatase, and alanine aminotransferase levels were similar among the diet groups

Alanine aminotransferase levels were significantly reduced from baseline to 24 months in the Mediterranean-diet and the low-carbohydrate groups.

The Good, Bad, and Why oh Why?

Overall, most reporting on the study today, feel the research team did a good job designing the study and executing it, many applauding the high rate of retention in the study for two years. I too am impressed that the participants remained committed to the trial, their assigned diets, and the longer-term outcome measures!

I personally would have liked more information than was published.

Key information regarding the baseline diet was not included in the data - not published items include how many calories were consumed, on average, at baseline; nor do we know how much protein, carbohydrate, fat or fiber was in the baseline dietary habits of those participating. While obviously not critical, it is 'nice to know' data.

I also would have liked to see the researchers have the courage to actually follow the Atkins dietary approach, and not make changes based on a number of assumptions.

We do not, for example, know what the outcome would be if the participants on the low-carb dietary arm had not been told to specifically choose vegetable based fats over animal fats. Atkins does not specifically state you must eat butter, but the diet allows butter. In addition, encouraging the consumption of plant-based proteins over animal proteins is another tweak that may not have had any effect, or may have had a positive or negative one. We simply do not know because the researchers encouraged plant-based protein consumption rather than leave the dietary recommendations as they are - meats, eggs, poultry, fish, tofu and such are allowed, ad libitum. [please see update below!]

The reporting in the media, as my earlier post highlights, has been quite an eye-opener. I'm not sure if those quoted realize it or not, but their reaction to the study is quite telling, especially those with the strongest vested-interests in maintaining the status quo.

In the Wall Street Journal, Robert Eckle, the past president of the American Heart Association and a professor of medicine at the University of Colorado Health Sciences Center, said he was not ready to recommend an Atkins-type low-carb diet based on the results. People on a low-carb diet increased their consumption of saturated fat, he said, which could not be good for them in the long run.

Did he even bother to read the findings?

Or maybe he was just disappointed the AHA's recommended diet - the diet recommendations the low-fat group were instructed to follow - did so poorly compared to the other two?

Did he know that the study author, Dr. Meir Stampfer of Harvard Medical School, in the same article, said "It is time to reconsider the low-fat diet as the first choice for weight loss and for cardiovascular health, it is not the best."

I think tomorrow, we'll take a fun ride through many of the quotes and opinions offered on this study!

In the meantime, what are your thoughts? Feel free to leave comments!

UPDATE 7/18/08

I received an email today from a friend who asked one of the researchers about the reference to plant-based (vegetable) fats and proteins. Dr. Shai assured him that the low carbohydrate group was not advised to consume a vegetarian low-carb diet, nor were they specifically restricted from eggs, cheese, red meat, poultry or fish. Due to dietary restriction (religious) the group would not, for instance have a cheeseburger or butter on top of their steak. Olive oil featured prominently. The participants did read the Atkins diet book. And the examples provided of the types of meals was "For example, a plate could include : fish or fried/not bread coated chicken/or red meet, broccoli and mushrooms coated with eggs, roasted eggplants, vegetable salad (peppers, cucumber, green leaves, notlettuce) with olive oil dressing.


  1. Anonymous7:41 PM

    As the low CHO group still had carbohydrates as 40% of energy I find it difficult to draw too many conclusions about low carb diets in general.(My intake is round about 20%)

  2. Anonymous8:57 PM

    Thanks as always. I'm a long-time lurker. Your analysis of the study is much appreciated. Examines many of the questions that I raised, especially about the advice to eat vegetable protein. Since when are 120 grams of carbs considered a low-carb amount?

  3. Anonymous6:57 AM

    The medical profession is still foisting carb consumption and vegetable oils over saturated fats on a public that grows increasingly fatter and unhealthier. Thanks for your voice in the wilderness. I would encourage everyone to read Gary Taubes' Good Calorie, Bad Calorie if they have not already done so. Personally, I try to follow a no-carb diet as much as possible because at my age it is the only way I can maintain or lose weight. It is very odd to me that despite repeated warnings folks still smoke, consume too much alcohol, refuse to weat crash helmets and seat belts, yet if you tell someone that they would be much better off consuming red meat three times a day they are totally horrified. Whatever!!

  4. Anonymous10:12 AM

    Regina - thanks for you take on this study. I too find it incredible (though not unexpected) that there is such a disparity in interpretations of this study. You can really tell those who are still worshipping at the feet of Dr. Dean Ornish, by their commentary.

    I did catch one paragraph with a typo, and perhaps an additional needed wording, to make it more clear what you are referring to.

    What the researchers did not note in their written text of the results was this - the low-carb dieters had similar declines in their fasting blood glucose levels through month 12, followed by a progressive decline through month 24.

    I think what you meant to say was …the low-carb dieters with diabetes had similar declines in their fasting blood glucose levels through month 12, followed by a progressive increase through month 24.
    (bold - my changes/addition)

  5. I wish they would quit playing around as well. Just have people eat bacon and brie and see what happens. I think everyone would be surprised!

  6. I'm not surprised fasting blood sugar and IR was not reduced more in low carb. A high fat, high calorie diet will cause physiologic insulin resistance. This is why all doctors familiar with low carb diets advise patients only to have a glucose tolerance test after eating a normal diet for 1 wk. The results are invalid, as long as the diet was low carb, because low carb diet makes it difficult to metabolize glucose (much in the way a high carb diet makes it impossible to use fat energy effectively, the reverse is true - a diet based of fat makes it difficult to make energy from high glucose).
    I suspect if the low carb group were fed a normal diet before the test, they would have had outstanding insulin tolerance and their fasting blood sugar would be even lower than the med diet.

    Also, another issue is the fact low carb was ad lib calorie. IF low carb were calorie restricted like the other two groups, the results would have been much better, and I'm certain fasting sugar would have been the lowest of all.

    That low carb had higher fasting sugar, as well as higher blood pressure, is evidence they were eating a lot more calories than the other two groups. We would have observed the lowest blood pressures and the lowest fasting sugar if fat calories were restricted.

    The ironic thing is, even when low carb is crippled as in this study, it still more or less blows apart the alternative diets.

    Regarding the reporting of the study...
    I don't expect opinions to change. Ever. If they don't realize low carb is worth a look by now (2008 people!) then at this point I must conclude they are purposefully deaf and ignorant.

    I think government financed health care is the only way for the shill game to end (where they sell us cures that actually make us sick). The government is not going to pay for useless medicines and expensive surgeries when a low carb diet works more effectively, you know? In other countries with national health care, we couldn't have the shameful swamp mess we have today in america, where drugs are advertised on TV and useless/unnecessary surgeries (like gastric bypass) are routine. Then the physician could earn a living practicing preventative and curative medicine; in america, the reverse is true - a physician who prevents disease is a poor physician. There's no money in promoting a low carb diet... and patients are very adverse to it, because all of the sheisters promise they can have the same results in a pill/surgery (or alternately, that the low carb diet is dangerous/ineffective, so they better take the pills/surgery because that is so much safer, lol?)

  7. It is impressive that the (sort of) low carb diet resulted in greater weight loss, even though calories weren't restricted. How would low fat have come out if people got to keep eating when they were still hungry?

  8. Thank you for going though all of this, it's interesting but although the results may encourage some of the many doubting medics to at least look at alternatives to the low-fat message, I suspect it will be all too few of them.

    The degree of resistance to any change of mind or opinion is incredibly strong, even when faced with incontrovertible evidence.

    I know it's no scientific study, but my partner's situation shows how closed some minds can be. He is diabetic and has a heart condition was extremely diligent for many years in sticking to the conventional dietary advice. Meanwhile his numbers became ever worse and his drug doses ever higher.

    Then I persuaded him to try low-carb just 10 months ago. He had a medical this week.

    For the first time in 12 years his BP is normal. He has lost weight (though he was only ever mildly overweight anyway), his cholesterol and triglycerides are those of a normal healthy adult, and his glucose/insulin numbers are too.

    But here is the extraordinary thing.

    He started to tell the doc about the changes he had made in the way he ate - he'd tried to tell him in the past but it was getting a very cool response so he backed off. The man went CRAZY - all sorts of dire warnings issued forth, he was going to kill himself with such an unhealthy way of eating, it was an extremely dangerous diet for someone with his history of heart disease/diabetes, all those changes were because the drugs were working. STOP IT AT ONCE!!!!

    Closed minds.

    My partner hadn't the courage to tell him that he wasn't actually taking any of the diabetes drugs anymore and had tailed off the dosages of most of the others quite significantly.

    I'm well aware this is a way less than ideal situation and that honesty between doctor and patient should, in an ideal world, be paramount. But my partner really does not want to change his doctor. So it's DIY to some extent for us for now at least.

    And by the way I live in a country that has socialised medicine. It does NOTHING to change the fact that most doctors learned at least 95% of what little they know about nutrition from some drug company or other peddling a pill to cure the ills of the same poor nutrition they continue to recommend. It does mean though that we at least don't have to pay for the drugs he is pretending to take.

    So it's a very, very encouraging study, but I'm afraid it won't be nearly enough.

  9. Anonymous11:29 PM

    Thanks for your analysis, Regina. Here are a few of my comments.

    1) The first "anonymous" comment above is right about the low-carb diet not being much of a low-carb diet, especially compared to its namesake, Atkins. At 24 months, the low-carb dieters were getting 40% of their daily calories as carbohydrates. (The other two groups were eating 50% of energy intake from carbs.) This still seems like a lot of carbs on the Atkins diet. A gram of carbs has 4 calories. The stated carbohydrate goal for the low-carb cohort was a maximum of 120 grams of carbs daily, on a diet of 1800 calories. So 120 grams of carbohydrate should be 27% of total daily calories. At no point did the low-carb group reduce their average percentage of calories from carbohydrates under 40%. OK, maybe be in the first two weeks but those data are not reported. On an 1800 calorie diet, 40% of calories from carbs would be 180 grams. You gotta wonder if weight loss would have been greater if the dieters had been more compliant. But you could say that about the other cohorts, too.

    2) Like you, I wish the researchers had provided baseline caloric intake. You can, however, find baseline macronutrient composition (i.e., % of calories from fat, protein, carb) in Table 2 of the study.

    2) The "low-fat" diet was not much of a low-fat diet, either. Baseline percentage of calories from fat in the low-fat cohort was 31.4%. The participants dropped this all the way to 30-30.8% during the study.

    3) Dr. Eckels correctly noted that the low-carb dieters increased their percentage of calories from saturated fat, from 10 to 12% of total calories. But if indeed they were eating fewer total calories, total saturated fat grams may have been lower than baseline. BTW, the other two cohorts derived 9.6% of calories from saturated fat, same as at baseline.

    4) Am I the only one wondering if an Israeli gene pool impairs generalizability of the results to U.S. populations? Who works at the Israeli nuclear research facility in Dimona, where the study was conducted? Is it an international, heterogenous gene pool?

    Anyone interested in my full analysis can read it free of charge here:


  10. Dave,

    Thanks for your thoughtful reply. I agree with it, except for the elements of time and scale. All of the coaches you mention built their teams over many years, developing talent, schmoozing donors and administrators, and finally, recruiting. If any of the coaches you mention had promised a national championship to their schools after one year in their job interviews, they would have been laughed out of the room.

    Obama is brand-new to the national scene. He hasn't had the time a politician needs to build the network of relationships he needs to successfully lead a large enterprise. Of course, experience alone in government alone isn't the only criterion for success as president, but it is one the prerequisites.

    Regarding Brezinski's alleged sagacity about the Iraq war, that scarcely required much brain power. All he had to do was read the writings of the elder Pres. Bush, and pick up a few tidbits from all the generals in active service at the beginning of that folly.

  11. A couple of things, I think this study shows that there is more than one healthy diet, and that the real culprit it the western dietary pattern is processed foods as much as it is "Carbs". Here and on a couple of boards, the anglo-centric nature of Atkins as practiced, versus the cultural and religious laws of conservative Judaism, not to mention the expense of meat, required a few changes to the way the diet would need to be implemented. From my perspective, one of the biggest take homes from this study is that fat and fiber are important to health.

  12. My name is Dr James Carlson and I have been using low carb diets in my practice for over ten years. My only comment is "No kidding, I have seen these results thousands of times over the years." When will the medical community wake -up and realize low carbs are NOT an option, it is the way we all should be eating. I actually wrote a book entitled GENOCIDE; HOW YOUR DOCTOR'S DIETARY IGNORANCE WILL KILL YOU. The title Genocide reflects the fact that millions of people die each year, due to physician's dietary ignorance. Click on the link below to check out a few chapters of my book for free.

  13. Anonymous11:08 AM

    Finally a good comparison of the differences between the two diets! I've always wondered if a low cab diet was really better. I figured it would, but didnt know for sure.

  14. It is impressive that the (sort of) low carb diet resulted in greater weight loss, even though calories weren't restricted. How would low fat have come out if people got to keep eating when they were still hungry? Thanks very good work.Radialabs

  15. Those who actually completed the study are the data I prefer to look at for weight loss since it accurately presents how effective the dietary approaches are when continued for two years!