DrSears.com creator of the Zone Diet

Dr. Sears comments. Those women with the lowest risk of heart disease consumed a diet with a protein-to-carbohydrate ratio of 0.55 (a Zone Diet) whereas the women with nearly twice the risk of heart disease consumed a diet with a protein-to carbohydrate ratio of 0.27. That ratio is virtually the same as recommended by the USDA Food Pyramid. This Harvard study strongly suggests that women following the Zone Diet would have a 50pct. less likelihood of heart disease compared to women following the USDA Food Pyramid.

Dr. Sears Comments. This is another crossover study comparing the Zone Diet to a high-carbohydrate diet while containing equal amounts of calories and fat using healthy volunteers with normal lipid levels. The Zone Diet (with a protein-to-carbohydrate ratio of .5) showed statistically significant improvements in lipid parameters after only four weeks. Compared to the high-carbohydrate diet (with a protein-to-carbohydrate ratio of 0.3), the individuals following the Zone Diet had a 7pct. decrease in total cholesterol, an 8pct. decrease in LDL cholesterol, and a 27pct. decrease in triglycerides along with a 4pct. increase in HDL cholesterol. These same improvements in lipid levels for the Zone Diet have already been reported for hypercholesterolemic and postmenopausal women and male elite distance runners. It appears that everyone would benefit from following the Zone Diet.

Dr. Sears Comments. This article has tremendous implications (and potential warnings) for cardiovascular patients. The American Heart Association (AHA) Step II diet rarely works, thus forcing cardiovascular patients to use life-long cholesterol-lowering drug therapies. Now we know why. The AHA Step II diet increases triglycerides and lowers HDL cholesterol. The increase in the TG/HDL ratio has been shown by Harvard Medical School to be a powerful risk factor for the development of heart disease. On the other hand, diets with higher levels of monounsaturated fat decrease the TG/HDL ratio. This is why the Zone Diet primarily uses monounsaturated fat is its primary fat source and is not afraid to recommend fat. Hidden within the article is another reason for the poor results of the AHA Step II diet. the protein-to-carbohydrate ratio. The protein-to-carbohydrate ratio of the AHA Step II diet was 0.27, whereas the protein-to-carbohydrate ratios in each of the monounsaturated fat diets was 0.32. It is known that the lower the protein-to-carbohydrate ratio of a diet, the higher the higher the fasting insulin levels. Since fasting insulin is greatest predictor of future heart disease, any increase in insulin levels doesnt bode well for cardiovascular patients. If the study had used the Zone Diet (which has a protein-carbohydrate ratio of about 0.7), I believe the results would even better because a higher protein-to-carbohydrate ratio reduces insulin levels. Nonetheless, this study implies that the diets recommended by the AHA for the past 20 years may have been driving cardiovascular patients to be more likely to have a heart attack.

Dr. Sears Comments. This study appeared the same month that I presented our Type 2 data at the American Diabetes Association. The balance of macronutrients and amount of calorie restriction in this study was virtually identical to the Zone Diet. Not surprisingly, the clinical results were also virtually identical to our results. The most striking observation was that insulin resistance and fasting insulin levels were dramatically reduced within four days, and in the absence of any significant weight loss. This study also answers the chicken and the egg question. does weight gain cause increased insulin or does increased insulin levels precede weight gain The answer is the latter since insulin levels and insulin resistance are lowered prior to any weight loss. This study demonstrates that others can replicate the effects of the Zone Diet, and that the hormonal changes are seen within days.

Dr. Sears Comments. The article from Harvard Medical School provides strong supporting evidence that the Zone Diet (with a protein-to-carbohydrate ratio of 0.6) is superior to commonly recommended high-carbohydrate diets (with a protein-to-carbohydrate ratio of 0.2). In this crossover experiment, the weight loss was greater on the Zone Diet even though the calories consumed on both diets were identical. The statistically significant lower levels of insulin secretion can explain this unexpected result following the Zone Diet compared to the standard high-carbohydrate diet. In addition, patients on the Zone Diet maintained a positive nitrogen balance, whereas those consuming the high-carbohydrate diet were in a negative nitrogen balance indicating loss of muscle mass. Most important for long-term weight loss, when patients were given the opportunity to eat without any restriction on calories after six days, they ate 25pct. fewer calories after following the Zone Diet compared to when they consumed a high-carbohydrate diet.

What is a carbohydrate
Success with the Zone Diet depends upon restricting the amount of carbohydrates consumed while maximizing the vitamins and minerals derived from them. Unfortunately, many people have trouble recognizing what a carbohydrate is because they think of carbohydrates as only pasta and sweets. In reality, fruits and vegetables are also carbohydrates. An easy way to remember this is that carbohydrates grow in the ground, and dont move around. Pasta must be a carbohydrate, since it comes from wheat, which grows in the ground. Likewise, vegetables, such as broccoli grow in the ground, so they, too, must be carbohydrates. Finally, fruits, such as apples come from trees that grow in the ground, which makes them carbohydrates also. Although this may seem simplistic, the fact that fruits and vegetables are carbohydrates is a major revelation to many Americans.

INSULIN-STIMULATING CARBOHYDRATE CONTENT
Since the Zone Diet is about insulin control, you have to realize that not all carbohydrates affect insulin equally. Every complex carbohydrate must be broken down into simple sugars and will eventually enter the bloodstream as glucose, which in turn will have a stimulatory effect on insulin secretion. Fiber (both soluble and insoluble) cannot be broken down into simple sugars, and therefore it will have no impact on insulin. Taking this into account, I developed the concept of insulin-stimulating carbohydrate content for a food. Simply stated, this is the total amount of carbohydrate a food source contains minus its fiber content (which is usually included in determining the total amount of carbohydrates).

If a carbohydrate source (such as pasta) has very little fiber content, then virtually all of its listed carbohydrate content will be insulin-stimulating carbohydrate. On the other hand, if a carbohydrate source is rich in fiber (such as broccoli), then its insulin-stimulating carbohydrate content will be significantly reduced. This means that more volume of fiber-rich carbohydrate source must be consumed to have the same impact on insulin secretion as a much smaller volume of low-fiber content carbohydrate (see Table 1).

Table 1. Amounts of Insulin-Stimulating Carbohydrates in Various Food Volumes

Food

Volume

Total Carbs (g)

Fiber (g)

Insulin-stimulating carbs (g)

Pasta Apple Broccoli

You can quickly see that you would have to eat a tremendous volume of broccoli (approximately 12 cups) to have the same impact on insulin as eating a relatively small amount of cooked pasta. This is why starches and grains are considered high-density carbohydrates, whereas fruits are medium-density carbohydrates, and vegetables are low-density carbohydrates. The Zone Diet relies heavily on low-density carbohydrates, so large volumes of food must be consumed in order to have an appreciable impact on insulin. This is also why high-density carbohydrates are used in moderation on the Zone Diet because very small volumes can stimulate excess insulin production.

ZONE BLOCKS OF CARBOHYDRATE
Zone Food Blocks are simply a way of putting various carbohydrates on an equal footing regarding their insulin-stimulating effect. I define a Zone Block of carbohydrate as a volume containing 9 grams of insulin-stimulating carbohydrate. So lets return to the above example, and determine the approximate amount of Zone Carbohydrate Food Blocks in each of the sources (see Table 2).

Table 2. Zone Food Block Calculations

Food

Volume

Insulin-stimulating carbs (g)

Approx. Zone carb. blocks

Pasta Apple Broccoli

These numbers arent too easy to remember, so I simplified them by normalizing the volume of the carbohydrate source required to make one Zone Carbohydrate Food Block. This is accomplished by dividing the volume of a carbohydrate source in Table 2 by the number of Zone Carbohydrate Food Blocks in that same source. Then you round that number to an approximate volume that you can easily remember, as shown in Table 3.

Table 3. Zone Carbohydrate Block Calculations Simplified

Food

Zone carb blocks in volume

Volume of Zone carb blocks

Pasta Apple Broccoli
Now you have a way to compare carbohydrates directly with their ability to stimulate insulin secretion. A more complete listing of these Zone Food Blocks containing carbohydrates is found in the Zone Resources section of this web site.

The Concepts of Glycemic Index and Glycemic Load
One of the major nutrition breakthroughs was the development of the concept of the glycemic index. It was always thought that there were only simple and complex carbohydrates. The simple ones would enter the bloodstream rapidly, whereas the complex carbohydrates would be slowly broken down, thus providing sustained release over time. From this seemingly reasonable concept, came the nutritional wisdom that eventually led to the development of the USDA Food Pyramid.

Unfortunately, research began to rear its ugly head when investigators began to ask whether or not such simplistic thinking was justified. Lo and behold, it wasnt. Some simple carbohydrates, such as fructose, entered the bloodstream as glucose very slowly. On the other hand, some complex carbohydrates, such as potatoes, entered the bloodstream at a faster rate than table sugar. The explanation of this apparent paradox led to the development of the concept of the glycemic index.

The glycemic index is a measure of the entry rates of various carbohydrate sources into the bloodstream. The faster their rate of entry, the greater the effect on insulin secretion. There are three factors that affect the glycemic index of a particular carbohydrate. The first is the amount of fiber (and especially soluble fiber) a carbohydrate contains. the second is the amount of fat found in the carbohydrate source (the more fat consumed with the carbohydrate, the slower the rate of entry into the bloodstream). the third is the composition of the complex carbohydrate itself. The greater the amount of glucose it contains, the higher the glycemic index. whereas the more fructose a carbohydrate contains, the lower the glycemic index. This is because fructose cannot enter into the bloodstream without first being converted into glucose, a relatively slow process that takes place in the liver.

With time the glycemic index soon became the new fashionable guideline to determine which carbohydrates to eat. However, the glycemic index had significant experimental problems in dealing with low-density carbohydrates, such as vegetables.

The difficulties arose because determination of the glycemic index requires that a sufficient intake of carbohydrate (usually 50 grams) be consumed. But it is simply too difficult to consume this amount of carbohydrate from most vegetables at a sitting. For instance this would require consuming about 16 cups of steamed broccoli. As a result, nearly all the glycemic index work has been done with grains, starches, and some fruits, and virtually nothing is known about the glycemic index of low-density vegetables that are the backbone of the Zone Diet.

These difficulties have given rise to a more sophisticated understanding known as the glycemic load, which is far more important than the glycemic index in determining the insulin output of a meal. The glycemic load is the actual amount of insulin-stimulating carbohydrates consumed multiplied by its glycemic index. This reflects the reality that a small volume of high-glycemic carbohydrates has the same impact on insulin as a large volume of low-glycemic carbohydrates. Therefore, eating too many low-glycemic carbohydrates can have a major effect on increased insulin production. For example, black beans have a low-glycemic index because of their high fiber content. However, they are also very dense in carbohydrate content. As a result, eating too many black beans at a meal can have a very great stimulatory effect on insulin.

Ultimately, a healthy diet is obtained through insulin moderation, which can best be achieved by primarily consuming low-density carbohydrates that also have a low-glycemic index. That means eating a lot of vegetables. To illustrate this concept, Table 4 examines three distinct carbohydrate sources in the volumes which they are typically consumed. The glycemic load is the product of the number of grams of insulin-stimulating carbohydrate times the glycemic index for that carbohydrate. The lower the glycemic load number, the lower the insulin stimulation of that carbohydrate.

Table 4. Comparison of Different Glycemic Loads

Source

Typical volume (grams)

Glycemic index

Glycemic load

Pasta Apple Broccoli

*Estimated from the glycemic index of various boiled beans
Even though the glycemic index of each of these carbohydrates is about the same, 1 cup of pasta generates 20 times the insulin response as 1 cup of broccoli. And a single apple generates about 6 times the insulin response as the 1 cup of broccoli. It is clear that a glycemic load based on the serving size of carbohydrate is a much more valuable tool than using the glycemic index. Table 5 lists the various glycemic loads of a wide variety of carbohydrates. For vegetables that have never been tested for their glycemic index, I have used an estimate of 50 (although it could be considerably lower in reality) as I did in Table 4.

Table 5. Glycemic Loads of Various Tested Carbohydrates

Source

Typical volume

Grams

Glycemic index

Glycemic load

Fruits

Apple Apple juice Apricot Banana (med.) Cantaloupe Cherries Grapefruit Grapefruit juice Grapes Kiwi Mango (medium) Orange (medium) Orange juice Papaya (medium) Peach Pear Plum Raisins Watermelon Legumes Black bean soup Chickpeas (boiled) Fava beans (boiled) Kidney beans (boiled)Kidney beans (canned) Lentils (boiled) Navy beans (boiled) Pinto beans Soy beans (boiled) Breads and pasta Bread, dark rye Bread, sourdough Bread, white Bread, whole-wheat Croissant (medium) Hamburger bun Kaiser roll Linguine pasta (thin) Macaroni Pita bread Pizza Spaghetti Starches, grains and cereals Bulgur Cherrios

A good rule is that you should not consume a glycemic load of more than 3,000 units in any one meal. As you can see from the data, if you are eating low-density carbohydrates it is very difficult to have a meal with a high glycemic load. On the other hand, eating typical volumes of grain and other starch-based carbohydrates gives a meal a very high glycemic load and results in a far greater insulin response.

And you can also understand why many of the carbohydrates found in traditional grain-based vegetarian diets are likely to dramatically increase insulin levels. For example, white rice generates a tremendous amount of insulin response compared to the same volume of oatmeal or barley because rice has a greater glycemic load. Likewise, most breakfast cereals will have the same impact on insulin as a Snickers bar, since their glycemic loads are approximately the same. Meanwhile cooked vegetables represent a very low glycemic load, which is why they are a critical component of the Zone Diet.

But remember that the more processed a food, the higher the glycemic load. This is why boiled beans have a much lower glycemic load than the same volume of canned beans. And when you make any bean (like black beans) into a soup, the glycemic load skyrockets because the prolonged cooking breaks down the cell walls of the bean making it easier for the body to digest it into simple sugars for absorption.

Thus using the glycemic load concept, it is also becomes clear why consuming most of your carbohydrates from vegetables is the key to maintaining insulin levels within an appropriate zone.

VITAMIN AND MINERAL Contents
Another major goal in the Zone Diet is to consume as many vitamins and minerals as possible from carbohydrate sources with the least insulin-stimulating ability. This is easily achieved by using low glycemic load carbohydrates, especially vegetables, which are great storehouses for both vitamins and minerals, whereas fruits are especially rich in anti-oxidant vitamins. Starches, by contrast, are relatively poor sources of both vitamins and minerals, especially when you consider the amount of insulin they can stimulate.

In order to compare various types of carbohydrates, Table 6 lists serving sizes of typical carbohydrates that contain 1 Zone Block along with their vitamin and mineral contents.

Table 6. Vitamin and Mineral Content of 1 Zone Block Servings of
Typical Carbohydrates


A. Vegetables (cooked and drained) Its easy to see why most of your vitamins and minerals will come from vegetables coupled with additional fruits. You can also see why starches, grains, and pasta are very poor nutritional choices for virtually any diet considering the amounts of carbohydrates they bring to the table. This is why they are used as condiments on the Zone Diet.

Dr. SEARS. Well, it tells us soy is pretty close to a miracle food, if you use it in the construct of The Zone diet, which is all based upon a balance and moderation. Now, when we think of soy, most people think of things like tofu.

Over the years, Dr. Sears has developed a number of external indicators that predict with a fairly high degree of precision what your eicosanoid status is. These are the same ones that he first developed for the elite athletes in which he tested the Zone Diet for improving their performance. Each week the athlete would fill out an eicosanoid status report, and then fax it to him. Within 30 seconds, Dr. Sears could tell whether or not he would have to alter their intake of EPA and GLA to fine-tune their eicosanoid status. When the eicosanoids were perfectly balanced with proper supplementation, the reports would show no change from week to week. This eicosanoid status report appears below.

Dr. Sears comments. This abstract is a very compelling argument against the common nutritional mantra that a calorie is a calorie. Both diets tested were isocaloric, differing only in the macronutrient composition. The protein-to-carbohydrate ratio in the Zone Diet was 0.75, whereas in the American Heart Association Diet the protein-to-carbohydrate ratio was 0.25. The fact that exercise was part of the study also eliminated that factor in analyzing the data on weight loss and reduction of body fat. The fat loss in the participants following the Zone Diet was 260 percent greater than those following the American Heart Association Step 1 diet. This difference is even more impressive since participants following the Zone Diet consumed 20 percent more fat than the participants on the Step 1 diet. Furthermore, the fat loss in the Zone Diet was statistically significant (meaning it was reproducible) whereas the in the Step 1 group it was not. In terms of subjective measurements of fatigue reduction and increased vigor, the Zone Diet was again superior to the Step 1 diet. The lack of effect of the Zone Diet on triglyceride levels was probably due to inadequate levels of Omega-3 fatty acids in the diet. Unfortunately, fasting insulin levels were not analyzed in this study (as with other Zone studies) to correlate insulin reduction with loss of body fat. Other than those two items, this study is a very important step forward in the validation of the Zone Diet by other researchers.

Dr. Sears Comments. This article compared the Zone diet (still mistakenly labeled as a high-protein diet) to the diet based on the USDA guidelines. Not only was there greater thermogenesis(i.e. greater burning of calories) on the Zone Diet, but there was also no loss in muscle mass (i.e. nitrogen balance) and an actual decrease in GFR, which is indicative of improved kidney function.