Posted by: Joseph Dixon | June 12, 2014

Science: Unintended Consequences; Ancel Keys, Cholesterol, and the Transition to an Obese Society; Part XIX, A Short Review of Diets

There are thousands of books that have diets as their entire subject. I have dedicated just one chapter to diets because all diet books, and all popular diets, are derivatives of a very few number of diet possibilities.   The diet possibilities are:

1) Extreme macronutrient distribution diets

2) Inclusion or exclusion diets

3) Very low calorie diets

4) Diets with external psychological and/or structural support (usually diets that one pays for)

5) Diets that use eccentric or no preparation techniques (example: The Paleo diet)

Because all diets are based on a few very simple variations of the basic average American diet, the diets that have been recently popularized have actually been around for 50 years or more and every so often they have renewed popularity. An excellent review of an amazing variety of diets was presented in the book, “Rating the Diets,” by Theodore Berland and the Editors of Consumer Guide, published by Consumer Guide (Stokie, Illinois), Volume 77, April 1975. This guide reviews, in detail, many popular diets, including Dr. Atkin’s, Dr. Stillman’s, Mayo, Prudent, Zen, Simeons, Kennedy Hormone Diet Program, Cellulite Diet, Boston Police Diet, and many other diets. This review by the Chicago Tribune health columnist, Theodore Berland, is extremely well written and comprehensive.  It is also extensively referenced with early scientific articles describing studies of many of these diets.  Many of these articles have been forgotten, but they are still relevant and scientifically pertinent.

In my opinion, all diets are viable if they are healthy – for both the short-term and the long-term. People are different and they tend to gravitate to diets that fit their life style and basic tendencies.  I will only address the diets that are made up of different macronutrient contents, as these are the ones that are most often written about in books and in magazine articles.

In Chapter 7, I discussed the “Dietary Goals for the United States” that was released by Senator George McGovern’s committee, and the subsequent Dietary Guidelines released a few years later.  I included a table that presented the macronutrient breakdown of diets from a wide range of human societies.   This table illustrated the point that human groups were and are highly adaptable to different dietary macronutrient mixtures.

In the next table, I have compared the different main diets that rely on variations in macronutrient content that are popular today. In the left most column is the typical American diet as described by the USDA. In the second column is the low carbohydrate diet that is also called the Atkins Diet. In the middle column is the Zone high protein diet that many students in my class who are weight training adhere to. The fourth column is the very low fat diet, which is essentially a high unprocessed carbohydrate diet. And the fifth diet is the Mediterranean diet, which was first proposed and written about by Ancel Keys.

table diets for Ancel Keys obesity book

The typical American diet shown is an amalgam of many diets consumed in the United States. This diet is also called the “Western Diet.”

The Very Low Carbohydrate Diet

The low carbohydrate diet has been around for many years but has recently become popular again. It is predicated on the concept that high intakes of carbohydrates are obesogenic because they lead to an increased insulin level, which supports energy storage over utilization, and extremely low carbohydrate consumption prevents this. This is a complex metabolic issue and I will not discuss it right now.  A very important distinction here is that I am talking about the very low carbohydrate diet, where carbohydrate intake is at first set at 20 grams per day, which computes to just 80 kcal out of entire intake of 2000 kcal, or less than 5% of the total kcal intake.  And when intake is increased gradually to 50 grams of carbohydrate, carbohydrate intake is only increased to about 10% of total kcal intake.  This compares to the 50% of total kcal intake that carbohydrates provide in the typical American diet.  Because carbohydrates are so low in the diet, the very low carbohydrate diet is actually a high fat diet!  But most nutritionists feel that very low carbohydrate diets actually work, to some extent, because most kcal in our diet are supplied by carbohydrates, and when you eliminate carbohydrates, you eliminate total kcal from the diet. Therefore, lower energy intake occurs on this diet.  I have known several colleagues who like and prefer the very low carbohydrate diet and have used it to lose weight. They will follow the low carbohydrate diet for a month or two and then cycle back onto their regular diet.  Therefore, if the low carbohydrate diet appeals to someone, I applaud their use of this diet.

Several well known nutritionists have written negative reviews of the very low carbohydrate diet.

Dr. John Yudan, M.D., who was a Professor of Nutrition at the University of London, and who was a proponent of removing as much sugar from the diet as possible, commented in 1960, “We now also understand why this diet can lead to loss of weight in the obese. It is low in Calories, and it is this which causes loss of weight, and not some peculiarity in carbohydrates metabolism.”

Yudan, J and Carey, M. The treatment of obesity by the High-fat diet – the inevitability of calories. Lancet (Oct 29, 1960) pp. 939-941.

The negatives and positives of the very low carbohydrate diet are listed on the table.

Zone, High Protein Diet

The high protein diet provides at least 30% of kcal from protein and if possible more. Consuming 30% of kcal from protein sounds reasonable, but in reality it is difficult to obtain this much protein in the diet due to the naturally low content of protein in most foods. Another difficulty is that there are a limited number of protein rich foods, which leads to boredom when eating this diet. Also, a protein supplement often needs to be consumed to reach enough protein. The biggest plus of the classic high protein diet is that there are ample carbohydrate kcal in the diet that can be used for energy and to restock glycogen stores.

Very low fat/high carbohydrate diet

The very low fat/high carbohydrate diet is supported by several well respected medical authorities for the treatment and prevention of cardiovascular diseases such as CHD. Because this diet only contains about 10% of kcal from fat, the majority of kcal must be provided by carbohydrates. Therefore, the low fat diet is, in fact, a high carbohydrate diet. But the carbohydrates are derived from whole grain products. Also, there is a high intake of fruits and vegetables, so this diet also contains high fiber. Because of the composition of the diet, it is nutrient dense. The main problem with the low fat/high carbohydrate diet is that it provides low satiety due to the low fat content in the diet. Therefore, although there is no doubt that it is heart healthy diet, it is difficult for many people to stay on the very low fat/high carbohydrate diet. However, there are certain people who enjoy this diet and remain on it for their entire adult lives.

The Mediterranean Diet

The Mediterranean diet is in the far right column in the table, and this diet was first promoted in Ancel and Margaret Keys’ cookbook, “How to Eat Well and Stay Well the Mediterranean Way” (Doubleday, 1975). I will discuss the Mediterranean Diet in detail in the last chapter of this book. But if you look through the table, you will see that the Mediterranean diet maintains the approximate macro nutrient percentages of the typical American diet, but the ingredients and methods of food preparation are totally different. An important aspect of the Mediterranean diet is that it is a high fiber diet. Also, a recently published clinical trial confirmed that the Mediterranean diet was protective against diseases of the heart. I will discuss the Mediterranean diet in detail in the last chapter.

Since the diets presented in the table are based upon different variations in macronutrient content, I would like to discuss each of the macronutrients individually.


What Fats Should Americans Eat?

As discussed in an earlier chapter, there are over 10,000 different lipid species inside a cell. Therefore, a logical overriding strategy would be that humans should consume as wide a variety of fats from a wide range of foods as possible.  In previous chapters I discussed the most important functions of fats and cholesterol, but I was unable to cover every function they serve in the body. I also did not provide structures for the various lipid groups.  It is not the purpose of this book to cover every aspect of lipid metabolism.  In order to be exposed to a wider explanation of the functions of lipids and see their drawn structures, a recent book by Dr. Glen Lawrence would be a good place to start.

The Fats of Life: Essential Fatty Acids in Health and Disease [Paperback] by Professor Glen D. Lawrence, Rutgers University Press, 2013.

The next figure illustrates that humans should obtain nutrients, including fats, from many food sources.  The figure also shows why certain foods have a particular fatty acid composition.

Food Sources for Lipids

The algae on the left are one of the main sources of food for fish and other marine life. Algae are photosynthetic organisms and use photons from the sun to incorporate CO2 into cell molecules including lipids. Many different fatty acids are synthesized in algae but a large percentage are PUFA, including the omega 3 fatty acids EPA and DHA. Since ocean algae live their whole lives in the very cold ocean, it is important for their membranes to remain fluid and not to harden and freeze up. For this reason, algae incorporate EPA and DHA into the phospholipids of their cell membranes. When fish consume algae they receive high amounts of omega 3 fatty acids. Since fish cannot make their own omega 3 fatty acids, they utilize the omega 3 fatty acids from the algae for their own membranes. This allows the fish, too, to live in the cold ocean. Therefore, the fatty acid composition of fish resembles the fatty acid composition of the algae they eat.  Also, this is the reason why fish caught in the ocean are healthier than fish that are farm raised and fed grains as food.

Terrestrial plants also live exposed to harsh environmental conditions (temperatures vary from -40 °F to 110 ° F ). As with algae, plants use photosynthesis to synthesize fatty acids from CO2.   Most plants have the enzymes necessary to synthesize PUFA, especially omega 6 fatty acids. However, different from algae, plants have limited capacity to synthesize large amounts of omega 3 fatty acids. Therefore, although plants are good sources of PUFA, they are not good concentrated sources of omega 3 fatty acids. In the figure the overall content of PUFA falls from about 70% in algae to about 30% in plants, although this depends upon the specific plant studied.

When humans consume meat they consume the fatty acid pattern that is found in the animals from where the meat was derived from. In general, the fatty acid composition can vary based upon what the farm animals were fed. However, the fatty acid content of meat is usually more saturated and contains smaller amounts of PUFA. The monounsaturated fat content of the fat can vary considerably. Quite interestingly, the fatty acid content of animals that are free living and hunted by hunter-gathers often contains higher levels of PUFA than animals raised on a farm.

Finally, the fatty acid composition of cow’s milk is the most saturated of any other common food. The reason for this is that milk contains higher levels of saturated medium chain fatty acids, which may be better for digestion and utilization in young animals, including humans.

Since omega 3 fatty acids are so important for the brain, it is probably an excellent strategy to get a considerable amount of our dietary fats from sources on the left side of the figure. These sea foods are rich in PUFA including omega 3 fatty acids. However, there are other foods available that supply PUFA, and these are the land based plants. Early humans also relied upon whole grains and these should be included in the diet for both their fiber and PUFA. From what we know of Ancel Keys’ “Seven Countries” study, it is probably reasonable to obtain fat from the sources on the right side of the figure less frequently, although they can certainly remain in the diet at lower levels.

Because of the composition of fat in the foods presented in the figure, an intelligent goal for consuming these foods is to follow the recommendations shown in tan color on the slide. Recommendations for the main meals during the week would be:

Algae   – May become an important food source of omega fatty acids for humans some day! Who knows?

Fish and seafood – Eat twice a week as a main course

Plant foods and whole grains/legumes –   Eat at least 3 times a week as a main course

Meat – Eat as a condiment and maybe as a main source occasionally– Eat no more than 2 times a weeks as a main course. White meats are better than red. Chicken can be used as a main course.

Dairy – Eat sparingly – especially butter, which is concentrated milk fat; Eggs are a great sources of protein (6 grams per egg) – if you eat 2 eggs, only eat one yolk!

As long as you follow the above simple rules, you will not need to count the grams of fat that you are eating in your diet.

Conclusions on Fat

The above figure presents an improved way of looking at fat. We need to stop talking about Low Fat/High Fat in the diet. It is the type of fat that will either protect you, or lead to, after decades, to a multitude of chronic disease conditions!  If foods from all of the sources shown in the figure are eaten, then a wide range of different fatty acids and lipids will be consumed.


Since most of us consume enough protein, I have decided not to have an extensive protein section. Nutritionists believe that it a sensible to boost protein intake up to about 20% of total calorie intake (up from about 16%) to help maintain body weight. For most of us this involves boosting our protein intake by 25 grams per day! This is not as easy as it sounds, as protein rich foods tend to be more expensive. Reasonably priced protein bars (some providing 10 grams of protein per bar) can be used for a quick high protein snack. Consuming the Zone or High Protein diet is another story completely.  Boosting dietary protein kcal even further, up to 30% of total calorie intake from protein, is difficult and takes planning and determination. Most people following this strategy must use protein supplements or the consistent consumption of high protein sources such as meat and fish.

For example, on a 2500 kcal diet, providing 30 % of total kcal intake from protein means that a person on the high protein diet would need to consume 750 kcal from protein, which calculates to 188 grams of protein per day.  In order to eat 188 grams of protein one would have eat the following:

Food needed for 188 grams of protein

In order to understand how much protein this is compared to what is normally eaten, below is a short review of how much protein our body needs, how much is recommended, and how much most Americans consume per day.

Average protein requirement- Average amount of protein we need per day to survive

For a 70 kg man:  0.35 grams x 70 = 24.5 grams (Requirement)

For a 60 kg woman: 0.35 grams x 60 = 21 grams (Requirement)

RDA for protein- What is recommended to maintain health in almost all healthy people

Man: 70 kg x 0.8 g protein = 56 g protein   (RDA)

Woman: 60 kg x 0.8 g protein = 48 g protein (RDA)

NHANES III actual protein intake (average grams/day)- What we actually consume (average) per day

Man 19-30: 103 g/day (Actual Consumption)

Woman 19-30: 70.4 g/day (Actual Consumption)


Certainly it is possible to eat the high protein foods listed on a daily basis, but it may be difficult to keep this diet up for more than a couple of months due to the monotonous nature of eating similar foods every day.  However, there are people who like to eat a high protein diet, and when designed properly, the high protein diet may be effective for weight loss because total calories will decrease as one becomes disenchanted with consistently consuming high protein.


The intake of carbohydrates has increased during the period that obesity rates have increased. Earlier I showed that per capita consumption of corn sweeteners increased 4 fold from 1970 to 1997. Consumption of carbonated soft drinks also increased during this time.

Let’s take a closer look at carbohydrate intake during the increase in obesity rates.

Change in Carb intake AJCN

Total Carbs vs Fiber Intake AJCN 2004

Carb and BMI Figure AJCN

Total energy intake remained fairly constant until 1980 (data not shown). After 1980 total energy intake gradually increased until it reached approximately 500 kcal/day. Increased consumption of carbohydrate was the main contributor (428 kcal; about 80% of the increase). The remaining increases came from protein (12%) and fat (8%). During a 20 year period, the increase in consumption of dietary carbohydrates went from 48% to 54% of total energy intake while dietary fat fell from 41% to 37% of total energy intake.

Lee S Gross, Li Li, Earl S Ford, and Simin Liu. Increased consumption of refined carbohydrates and the epidemic of type 2 diabetes in the United States: an ecologic assessment. Am J Clin Nutr 2004;79: 774–9.

Conclusions on Carbohydrates

The data from Gross and colleagues above certainly point a powerful suspicion on the increased intake of simple sugars as an important contributor to the obesity epidemic.  As we discussed in an earlier chapter, many changes were occurring during this period of time.  As Michael Moss described so eloquently in his book, “Salt Sugar Fat: How the Food Giants Hooked Us,” published in 2013 by Random House, food companies started to add sugar and other sweeteners to their products in order to improve their bliss point, where the food becomes highly desirable.  Also described by Mr. Moss, food companies used the strategy of expanding product lines in order to provide a wide array of super palatable foods that fit every niche and are absolutely irresistible.  Certainly staying away from sugar and other sweeteners such as high fructose corn syrup would decrease the total kcal consumed.

A study investigated which diet was best for losing weight

Let’s discuss a study that tested several important diets.

Michael L. Dansinger, Joi Augustin Gleason, John L. Griffith, Harry P. Selker, Ernst J. Schaefer. Comparison of the Atkins, Ornish, Weight Watchers, and Zone Diets for Weight Loss and Heart Disease Risk Reduction  A Randomized Trial  JAMA, Vol 293, 43-53, January 5, 2005

Here are 3 out of the 4 diets Dansinger and colleagues tested:

Atkins diet – Start with less than 20 g of carbohydrate daily, with a gradual increase towards 50 g daily. (Also called Very Low Carb Diet!)

Zone diet – 40-30-30 balance of percentage calories from carbohydrate, fat, and protein. (Also called the High Protein Diet!)

Dean Ornish diet- Vegetarian diet developed by Dr. Dean Ornish containing 10% of calories from fat. (Also called the Low Fat/High Carb (Complex) Diet!)

Study Design.  The study was a 1-year randomized trial of the dietary components of the Atkins, Zone, and Ornish diets. Participants (160 individuals, about 50:50 men:women) were enrolled in the study conducted in Boston, MA. Each group contained about 40 individuals. Enrollees were adults of any age who were overweight or obese with a body mass index between 27 and 42. Each participant had to have at least 1 metabolic cardiac risk factor in order to provide motivation.

The participants were taught the diets through 1 hour meetings on 4 occasions during the first 2 months of the study. A dietitian and physician described the diets and gave general advice on how to adhere to each diet. Written materials and an official diet cookbook were given to each participant.  During the course of the study, food intake was monitored using 3-day food records at baseline, 1, 2, 6, and 12 months.

Results of the Study

After a year in the study, the mean weight loss was similar across all the diets. At 1 year, weight loss averaged about 2-3 Kg per person, or only a mean weight loss of about 2-3%. Also, the 1 year discontinuation rates were: Atkins, 48% stopped; Ornish, 50% stopped; and Zone diet, 35% stopped. So the Atkins and Ornish diets appeared harder to stay on, and more people adhered to the Zone high protein diet.  The above weight loss figures were means for the groups.  However, individuals did have successes.  Three individuals on the Ornish diet and 1 person on the Zone diet lost more than 20 Kg of body weight, whereas no one on the Atkin’s diet lost this much weight after one year in the study.

Conclusions from the study by Dansinger and colleagues (JAMA. 2005; 293:43-53):

“Our findings challenge the concept that 1 type of diet is best for everybody and that alternative diets can be disregarded.”

“…our findings do not support the notion that very low carbohydrate diets are better than standard diets, despite recent evidence to the contrary.”

“…poor sustainability and adherence rates resulted in modest weight loss and cardiac risk factor reductions for each diet group…”


Unless one adheres to a diet, the diet will not succeed, no matter which diet it is.

Therefore, one must conclude that rather than following a prescribed diet, one might be more successful following a healthy lifestyle! This was the exact conclusion that Ancel Keys came to and what he and his wife, Margaret, wrote about in their book, “How to eat well and stay well the Mediterranean way,” published by Doubleday in 1975.


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