The new study getting all sorts of publicity, especially among the low carb proponents, has come to a very interesting conclusion. One that people like Gary Taubes has been arguing for years. Not all calories are created equal. Here is Dr. Ludwig, the lead investigator of the study:

Here is how Mark Bittman of the NYTimes summarized the results of the Atkins group:

"The results were impressive. Those on the “Atkins” diet burned 350 calories more per day — the equivalent of an hour of moderate exercise — than those on the standard low-fat diet. Those on the low-glycemic diet burned 150 calories more, roughly equivalent to an hour of light exercise."

This was done with out exercising at all. Although this study is very small, it is particularly compelling because it was done in a controlled facility, feeding the study subjects every meal. This study could not have come out at a worse time for Marion Nestle who just wrote a book entitled "Why Calories Count". 

A quick look at the Amazon reviews of Mrs. Nestle's book has many 5 star ratings, with one very provocatively written 1-star review, posted on June 6. Here is what Mack90 had to say:

"After hearing one of the authors being interviewed on NPR yesterday, I bought the Kindle edition of their book. Given their title, I was particularly curious about how they addressed the evidence that indeed calories don't count nearly so much as the type of food eaten and that the "calories-in/calories-out" energy balance paradigm represents a misunderstanding of the First Law of Thermodynamics (see the articles on MedPage Today entitled "Food Fight Over Whether Hitler Made Us Fat" and also "Food Addiction: Cheesecake-Eating Rats and Obesity as a Mental Illness").

In 2007, author Gary Taubes published a 600-page book (including 114 pages of footnotes and references) entitled Good Calories, Bad Calories: Fats, Carbs, and the Controversial Science of Diet and Health. This book amassed and described a virtual mountain of evidence based on biochemistry, metabolism, physiology, endocrinology, epidemiology and clinical research that leads to the conclusions that:

1. Obesity is a disorder of excess fat accumulation and not the result of energy imbalance, overeating or sedentary behavior
2. Overeating and inactivity are compensatory effects and not the causes of obesity
3. We don't get fat because we overeat, we overeat because our adipose tissue is accumulating excess fat

So what data and arguments do Nestle and Nesheim muster to counter Taubes' evidence and conclusions? First of all, they don't even do it themselves, rather they bring in a surrogate, Dr. David Katz, to make their case. And what does Dr. Katz have to say? As quoted by Nestle and Nesheim, Katz asserts that the result of an anecdotal "N-of-1" experiment conducted by a single individual eating a "Twinkie Diet" is sufficient to invalidate or refute the arguments made in two books summarizing hundreds of studies over many decades (Taubes more recently published a streamlined and updated sequel (Why We Get Fat: And What to Do About It) to his earlier book. Moreover, Katz is hardly an unbiased judge of the evidence because he profits from his own commercial "NuVal(tm)" and "Flavor Point" diets that, if Taubes is right, might not be so compelling an approach to healthy eating and weight control or be good for his reputation as a diet blogger on The Huffington Post.

The use of a surrogate with an undisclosed conflict of interest represents intellectual cowardice (or laziness) and dishonesty (or carelessness) on the part of the authors of "Why Calories Count." This hugely negative aspect of the book calls into question the authors' reasoning and objectivity with respect to other arguments and conclusions made in their book."

Maybe Gary Taubes, and Mack90 are on to something...


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In Los Angeles in the 1960s, the Veteran's hospital would be the place of arguably the most rigorous clinical trial ever done, testing the potential benefits of a low saturated fat diet. Only three such trials took place in controlled hospital environments, enabling investigators to feed study subjects meals in which saturated fats were replaced with polyunsaturated fats while keeping the rest of the diet relatively unchanged, and this Veterans study was particularly well done. It was a double blind, randomized trial involving 846 subjects for up to 8 years. The subjects were former veterans, living in a domilicary unit. Half ate a control diet, similar to the American diet, and half ate the experimental diet. All meals were served in the cafeteria.

Dietary Intervention
Subjects were given meal tickets of a certain color, corresponding to a particular diet unknown to them. The control diet was 40% calories from fat, “mostly of animal origin,” and the experimental diet involved substitution of vegetable oils for 2/3 of the animal fat, incorporated into the diet in the form of milk, ice cream, margarine, and cheeses. In this trial the low saturated fat experimental diet produced a 13% reduction in serum cholesterol compared to the control group throughout the trial, objectively confirming the experimental group’s adherence to the low saturated fat diet.  

Outcome
After eight years of participation, there was no significant difference in heart disease rates, the primary endpoint, manifested as sudden cardiac death or heart attacks (78 events in 65 men in the control group vs. 60 events in 52 men in the experimental). However, when pooled with the data for cerebral infarction and "other secondary end points," the difference in total cardiovascular disease reached statistical significance, with 119 major events occurring in 96 subjects in the control group and 85 events in 66 subjects in the experimental group (p=0.01). 

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This clinical trial is all too often cited as supporting the diet-heart hypothesis. By reading the abstract, it seems reasonable, until you track down what these "secondary endpoints" happen to be. Which turned out to be quite difficult. After requesting an interlibrary loan from Pittsburgh, I eventually tracked down the ~80 page tome describing the study in vivid detail. And here are the secondary endpoints:

• ruptured aneurysms
• limb amputations due to peripheral vascular disease
• and “miscellaneous” events, such as occlusion of the mesenteric arteries
  

To say limb amputation and occlusion of arteries supplying your intestines is related to saturated fat intake would be a bit of a stretch. Extremity amputation was required if the dorsal pedal pulse and the posterior tibial pulse on the affected foot were absent or extremely faint. 

In other words, these "secondary endpoints" involved small arteries that supply the muscles on the top and bottom of your foot. 

Deaths due to non-atherosclerotic causes were higher in the experimental group (85 vs. 71 in control), resulting in near identical rates of total mortality (177 in control vs. 174 in experimental group). This study also raised an interesting question as to whether or not a diet high in unsaturated fat may contribute to death by other causes, since the experimental group had more non-cardiac deaths (specifically from cancer: 7 deaths in experimental, and 2 in control). However, these numbers are much too small to determine if this result was significant or not. Other such clinical trials have not supported this phenomenon. 

This study is another perfect example of how profoundly misleading an abstract can be, and how important it is to read each study in its entirety before making bold claims that this study supports the idea that eating a low saturated fat diet prevents heart disease. 

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In the 1960s and 70s, mental institutions offered dietary researchers an excellent opportunity to test various diets in a highly controlled setting for a long duration. At the time, long term mental hospital stays were common, and researchers used this to their advantage. This opportunity was famously utilized three separate times, in Los Angeles, Helsinki, and Minnesota. In each city, researchers tested the long term effects of eating a low saturated fat diet, and how it may be related to developing cardiovascular disease. The last post discussed the pitfalls involved in blinding a diet study, and the Minnesota Coronary Survey is an example of quite the contrary. 

This was a double-blind randomized control trial lasting 4.5 years in 6 Minnesota state mental hospitals and one nursing home involving 4,393 men and 4,664 women. It examined effects of a lipid lowering diet on heart disease. This was the largest study by far that tested the diet heart hypothesis, and they did so with arguably the most rigorous study design to date.

Each patient was randomly assigned to consume either the low saturated fat intervention diet (38% fat diet; 9% Saturated fat, 15% polyunsaturated fat, 14% monounsaturated, 166 mg cholesterol), or the control diet (39% fat diet; 18% saturated fat, 5% polyunsaturated fat, 16% monounsaturated fat, 446mg cholesterol). The difficult part then, is to create two different diets containing these macronutrient compositions that are not discernable by taste or smell. The next challenge is serving over 9,000 people their correct diet for years, based on which group they were randomly assigned to. Here is how they did it:

"Both diets were served in a single line. As a participant entered the line, he or she was handed a label bearing his or her name and a code number that was incomprehensible to the uninitiated but easily interpreted by the foodservers to determine which diet was to be served...The label also enabled the food service worker to serve the proper tray without compromising the blind design, and the labels remaining on the sheet provided the basis for the daily tally of missed meals. Each month the hospital technicians transferred the missing meals data to a "Port-o-Punch card." These cards were read by the computer and at the end provided a correlation between adherence and cholesterol response"

To compliment the rigorous study design, the cholesterol levels of the patients can be used as an objective marker throughout the study to make sure everything is going as planned. Since we know from feeding studies that when you replace saturated fats with polyunsaturated fats, total cholesterol levels decrease, researchers can use this phenomenon to measure adherence. Here is a graph of the cholesterol levels of the study subjects over the course of 4+ years on their respective diets:

Intervention group cholesterol levels decreased 14.5% and were stable for the entire study. The stability of these graphs is spectacular, offering an excellent test of the diet heart hypothesis. Those who kept their cholesterol levels 14.5% lower for 1-4 years should have less heart disease. However this was not the case.
After 4.5 years, no reduction in cardiovascular events or total deaths from the treatment diet. In fact there was a non-significant trend towards a benefit to a high saturated fat diet:

Although the trial laster 4.5 years, not everyone consumed the diet that long. The main criticism of this study was the average length of time on the diet, which was 384 days. However, the number of person years observed was 9,538, with 5,903 of these years continuously for more than 2 years and 2,495 for more than 4 years. 

The authors waited about 16 years before publishing this data. According to Gary Taubes in Good Calories, Bad Calories, when he asked Dr. Frantz, the principal investigator, why they waited so long to publish the study, he explained in an interview: "We were just disappointed in the way it came out."

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Tried a paleo or carbohydrate-restricted diet? Join the registry today and contribute to a better understanding of this way of eating. 

I had lost about 35 pounds counting Weight watchers points and kept it off for 10 years. But, I was hungry all the time, even though I ate every 3 hours. I read about low-carb diets in reader's Digest in 2011, got the books by Jonny Bowden & Gary Taubes, and slowly eliminated the bad carbs from my diet. I was amazed at how my hunger subsided.

I didn't aim to lose any weight, just not be hungry constantly, but I lost about 15 pounds without trying! I eat more calories than before and quadrupled my fat intake. 

I play a lot of competitive tennis, and I can tell that my performance has greatly improved on the court. I can play 3 long sets and outlast my opponents. I used to "crash" around 5pm (especially on tennis match days), but now I am a bundle of energy! 

Also, one of the best things I first noticed is how acute my thinking became---so wonderful!!! Also, I never thought I had inflammation in my body, but once I went low-carb, I had a sharp decrease in those aches & pains we chalk up to getting older. My body composition has been changed, too. I look much more muscular, but still feminine. 

What was the biggest challenge to adopting a carbohydrate-restricted or paleo diet?
Getting over the "avoid fat" message that we all hear.

What advice (if any) would you give to someone interested in trying a carbohydrate-restricted or paleo diet? Were there any obstacles that you overcame that could help future dieters?
I learned to cook baked goods with ingredients like almond flour, flax meal & coconut flour. Actually, that was great because I can eat cookies, pancakes, etc. again (low-carb versions), where before I restricted myself. The real food I eat tastes so much better than the "low-fat" garbage!!!!!!


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Tried a paleo or low carb diet? Join the registry today and contribute to a better understanding of this way of eating!

The randomized clinical trial offers our best tool for determining the efficacy of an intervention as compared to another. Whether it is a drug trial or diet trial, the devil is in the details. Reading the abstract does not give you the whole story, and it can be profoundly misleading. 

For example, let us assess a popular randomized clinical trial testing the efficacy of different diets, performed by some of the biggest names in diet and obesity research, such as Dr. Frank Sacks and Dr. George Bray.

The conclusion of their study is simple. All diets are created equal. 

This is the headline that makes it into the newspapers and becomes accepted as fact. Why question the results? Dr. Bray and Dr. Sacks and very well respected world-wide for their work; The New England Journal of Medicine is a prestigious journal. No sub-par work would get through the cracks. 


When reading a dietary clinical trial, and assessing its internal validity, there are three major points to keep in mind:

1. How large was the difference between assigned exposures?
2. Is there any evidence that the study subjects followed the diet or intervention they were randomized to?
   
3. When assessing a study testing varying carbohydrate content, is there any difference in triglyceride levels between the groups?

Difference between assigned exposures
The nutrient goals for the four diet groups were:

Low fat, average protein - 20% fat , 15% protein, and 65% carbohydrates 

Low fat, high protein - 20% fat, 25% protein, and 55% carbohydrates 

High fat, average protein - 40% fat , 15% protein, and 45% carbohydrates

High fat, high protein -  40% fat, 25% protein, and 35% carbohydrates

This was how they described it in the paper. Of course, the low fat, average protein group could also be called high carbohydrate group, and the high fat, high protein group could be called low(er) carbohydrate group.

Right away, this study design is somewhat worrisome, since the carbohydrate content of the diets are relatively similar. Determining a 10% difference in macronutrient content is likely unrealistic, since study subjects tend to cheat on their diets and the dietary assessments are subpar. This concern is further compounded by this seemingly innocuous sentence buried in the methods:

"Blinding was maintained by the use of similar foods for each diet."

At first glance this would be great. Blinding adds to the rigor of the study design, by keeping the study subjects in the dark as to which intervention they are receiving. However, in a diet study, this is very difficult. The only way this can be done properly is when foods are chemically modified to contain different nutrients, while still maintaining the same look, smell, and taste of the original food. This has been done beautifully in the Minnesota Coronary Survey, testing the potential benefits of a low saturated fat diet. Although rarely mentioned in the scientific literature, it was a very large, double blinded study that chemically altered the fat composition of various popular foods served to the institutionalized study subjects. (On a side note, this study found absolutely no benefit to eating a low saturated fat diet.)

However, blinding a study comparing different percentages of carbohydrates, protein and fat is essentially impossible without making each intervention very similar.

Is there any evidence that the study subjects followed the diet or intervention they were randomized to?

This is the giant elephant in the room of every dietary clinical trial. It is an enormous problem that nobody really talks about, and it is the major inspiration for developing PhotoCalorie. The "gold-standard" in dietary research in the year 2012 is pen and paper. We have machines that can literally look through your skin and see your organs and bones in vivid detail. We can tell who your parents are, simply by a drop of your spit. Yet when we study obesity, arguably the most important disease that plagues the world today, we use technology from 1812. 

In this particular study, the gold standard was not used. They instead used a 24-hour recall twice throughout the 2 year study in 50% of the patients. In other words, out of the 730 days and 811 study subjects, the primary intervention was only measured on 6 days in 405 people. 

6 DAYS! 0.8% of the days. Assuming they ate 3 meals a day, this means out of 2,190 meals they ate, only 18 of them were reported!

Compounding this unfortunate number is the fact that a 24-hour recall is far from perfect, and people tend to forget what they ate, and report foods deemed healthier more often.

Given all these limitations, here is what the study subjects reported eating. The left three columns correspond to the low fat, average protein group and the right three are for the low fat high protein groups, at 6 months and two years follow up:

As you can see, the macronutrient composition is virtually identical. At 2 years the low fat, average protein group was eating 1531 calories, 53% from carbs, 19.6% from protein, and 26.5% from fat. The low fat high protein group was eating 1560 calories, 51.3% from carbs, 20.8% from protein, and 28% from fat.

When assessing a study testing varying carbohydrate content, is there any difference in triglyceride levels between the groups?

There are other, more objective ways, to assess dietary adherence in such studies. When comparing groups with varying levels of carbohydrates, one excellent tool is the triglyceride levels in the study subjects. Simply stated, when people eat lots of carbs, their triglycerides go up (and their HDL usually goes down). Here is the data from the Sacks study:

The triglyceride levels at 6 months and 2 years are virtually identical. Same with the HDL levels. 

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The authors conclude in the discussion that the  "principal finding is that the diets were equally successful in promoting clinically meaningful weight loss and the maintenance of weight loss over the course of 2 years."

When you combine all these clues together -  the blinded study design, the similar reported macronutrient intake, the identical triglycerides and HDL levels - you come to a dramatic conclusion that explains why all the groups were equally successful: They were all eating the exact same diet!


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Being genetically predisposed to corpulence, I have battled with weight issues since my teenage years. Low fat, calorie restricted diets did work for a time, but I would inevitably gain the weight back. As I aged, even these diets proved ineffective. In April of 2001, I began a low-carb lifestyle, deciding that whatever diet I started, I would do it for the rest of my life. I cut sugars and starches from my diet, and eat adequate protein, good fats, lots of green vegetables, and some berries. I started at 167 and I now weigh 125. I went from a size 14 to a size 6 and have kept the weight off for almost 11 years. My cholesterol levels have improved, I am in perfect health, with a significant increase in energy, and no hunger. I am happy to continue this eating plan for life.

What was the biggest challenge to adopting a carbohydrate-restricted or paleo diet?
I am a people pleaser, and the biggest challenge for me was having to tell people that I could not eat the food they offered me.

What advice (if any) would you give to someone interested in trying a carbohydrate-restricted or paleo diet? Were there any obstacles that you overcame that could help future dieters?
Believe that a low-carb plan will work for you. It is a learning experience, so relax, enjoy the journey, and don't be discouraged if you make mistakes. Even if you stall for a while, you are still going in the right direction. Also, let it be well-known that you are following a low-carb plan so that your host/hostess is not offended when you refuse a high carb dish.

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Tried a paleo or carb-restricted diet? Join the registry today and contribute to a better understanding of this way of eating.