Enter the Snake Oil Zone

January 1997
by Steven Novella, MD

Every half decade or so another fad diet makes an appearance. Such diets rise in popularity, win converts, make a great deal of money for their authors, and then eventually fade to obscurity. Added to this is the endless stream of supermarket tabloid claims for new breakthroughs which promise easy weight loss without calorie restriction or exercise. Although such diets vary greatly in detail, they share several fundamental characteristics in common. Enter The Zone by Barry Sears is just the latest in this particular genre of popular pseudoscience.

Americans are the most overweight population in the world, one quarter to one third of adults. And yet as a society, we highly value the healthy and sexy image of thinness. The result is a multi-billion dollar industry selling weight loss. It is no wonder that at any given time there is likely to be one or more diet books on the best-sellers list. Some of these self-help books actually contain accurate and useful information, because they are responsibly written and are faithful to current medical knowledge. Most, however, are simply fad diets selling false promises. How can the consumer tell the difference?

Modern principles of weight loss are actually quite simple. The only way to lose weight is to burn more calories than one consumes. There is no way around this simple and logical fact. One pound of fat contains 3,500 calories, therefore a calorie deficit of 500 per day will result in one pound per week of weight loss. The way to achieve this goal is to restrict calorie intake, while maintaining a well balanced diet, and/or increase calorie expenditure through exercise.

There are now many studies which confirm the conventional wisdom that long term successful weight loss, resulting in a longer, healthier life, results from having sensible eating habits and an active lifestyle. There is no quick fix. Monotonous or heavily restrictive diets are usually unhealthy and have a 95% long term failure rate. Exercise too is essential, but there is no magic exercise that can result in spot weight reduction.

What is a healthy diet? In a word, balanced. This means eating a good variety of foods, so as to receive an adequate supply of vitamins, minerals, essential fatty acids and essential amino acids. Macronutrients – carbohydrates (sugars and fiber), protein, and fat, should also be balanced, although there is probably a wide range of acceptability. There is good information that a relatively low fat diet decreases the risk of certain types of digestive system cancers1, reduces the risk of heart disease2, and aids in calorie restriction because fat contains more calories per gram, nine, compared to four for protein and carbohydrates. Also a high fiber diet seems to have these same health benefits. Current recommendations, based on the best information available, are for diets composed of no more than 30% fat by calories (although some recommend as low as 15%), 50% carbohydrates and 20% protein. This is obviously a brief summary of nutrition, but it is a reasonable one.

Exercise has many health benefits. Regular aerobic exercise results in calorie burning, but also in an increased metabolic rate, both of which aid in maintaining a lean body mass. Weight baring (anaerobic) exercise results in increased muscle mass, tone, and strength, which also increases basal metabolic rate. Exercise reduces the risk of heart disease, prolonging survival. There are also benefits in increased energy and having a more appealing physique.

Unfortunately, diet and exercise require a certain amount of effort and dedication, and Americans often have sedentary life-styles and poor eating habits. Who wouldn’t love to have a simple pill to take or a magic formula for easy weight loss without effort? Here the fad diet industry meets the public’s desires like a carnival barker selling amazing sights to a gawking audience.

Several rules will aid in the easy detection of such fad diets. 1) They typically claim that some combination of foods or macronutrients is the magical key to fat burning, resulting in weight loss without calorie restriction or exercise. Often there is one particularly good food to eat and/or one particularly bad food to avoid. 2) They rely upon anecdotal testimonials to support their claims rather than published scientific research. 3) They claim universal success. 4) They claim to be the result of a cutting-edge miraculous scientific breakthrough, or alternatively rediscovered ancient wisdom. 5) They claim persecution by the medical establishment.3 Those who have read my earlier articles will recognize these features as almost universal to alternative medicine in general.

Enter the Zone

The latest fad diet book, Enter The Zone by Barry Sears, PhD promises to be revolutionary, but, as we will see, is just the same old magical dieting claims warmed over, with some new disturbing twists. The basis of a Zone diet is, not surprisingly, a proper combination of macronutrients. This time the villain is carbohydrates. He coined the catchy phrase “The Zone” to represent this proper combination and extends his health claims well beyond mere weight loss. Sears develops an elaborate argument, couched in scientific terminology and combined with some legitimate physiologic concepts, but ultimately without any real scientific support.

The principles of the Zone diet begin with the claim that food is not mere sustenance, but is in fact like a drug that can have powerful effects on hormonal balance. Sears claims that “food in the most powerful drug you will ever encounter.” (pg. 27) Carbohydrates, he argues, result in insulin release. The more carbohydrates one consumes, and specifically the higher the glycemic index, which is the rate at which a food’s sugars are ultimately absorbed into the blood stream, the greater the insulin surge. Insulin is a powerful hormone with a host of effects, including a decrease in blood glucose by driving glucose into cells, increased glucose storage as glycogen, and increased fat deposition. In short, insulin is a storage hormone. Carbohydrates and insulin also have a cascading effect, resulting in an increased production of other hormones, as a class referred to as eicosinoids with a variety of their own metabolic effects. Sears credits “bad” eicosanoids with a host of negative health results, and claims that carbohydrates increase the relative ratio of these bad hormones.

Most of the basic science here is correct, although it is far more complex and beyond the scope of this article, or even Sears’s book. Where Sears goes astray is in the clinical conclusions he draws, without any justification, from these basic physiologic concepts. For instance, he argues that fat deposition results from insulin, and therefore if one decreases the carbohydrate content of food into the proper “zone” insulin levels will remain low and fat will not be created. In fact, it will be burned. Sears does not address the obvious question, however, of what happens to excess consumed calories, even if taken in a zone favorable combination – 40% carbohydrates, 30% fat, and 30% protein. (pg.71) He ignores the unavoidable conclusion that eventually, regardless of fluctuating hormone balance, excess calories will be stored as fat. They will not magically go away.

Conventional scientific understanding of these hormone systems states that they exist in a complex arrangement of feedback mechanisms evolved to respond to immediate metabolic needs and maintain long term homeostasis. There is no scientific basis to the claim that these systems can be permanently manipulated in one direction, namely fat loss, simply by altering the balance of macronutrients. Drugs can alter these systems, but they universally have multiple serious side effects resulting from disturbing the inherent balance of these regulatory hormones.

Let’s take a closer look at the alleged evidence that Sears presents to back his claims. I stated above that pseudoscientific fad diets offer testimonials and anecdotes in place of scientific research. Sears does not depart from this model, but he cleverly disguises his anecdotes as science. Sears calls his research “open pilot” studies. What this means is that they are uncontrolled, unblinded, and use small numbers of subjects. Such studies are used in science to test the waters, to get a basic idea if a direction of research has any promise, or any unanticipated risks. They are never used as the basis for firm conclusions.

As an example of Sears’s work, on page 22 he presents the results of one such study. He placed 91 people on a zone favorable diet. To his apparent amazement, their weight loss results were impressive, which Sears offers inappropriately as “proof” of his theories. Sears then calculates the p-value for his study. The p-value is the measure of significance of a study’s results. Basically, it is the probability, expressed as a decimal, of the study’s results being the outcome of chance alone. P-values are calculated by comparing the results of the study subjects with control subjects. But Sears’s study had no control subjects, so how did he calculate his p-values? Apparently, he used the outcome of no weight loss in place of the outcome of real controls. This is unheard of in modern science, because of the universal recognition of the need for blinded controls.

Without control subjects, observed in the same manner as test subjects, and placed on a diet with all known variables kept the same between the two groups except for those variables being studied, and without the subjects or evaluators knowing which subjects are on which diet, results of Sears’s study cannot be properly interpreted. No one can say if the weight loss is due to lower overall calorie intake, or a selection bias in which subjects volunteered for or stuck with the program, or the desire of the subjects and experimenters for a certain outcome. These are well known pitfalls in scientific research, which Sears either chooses to ignore or of which he is completely ignorant.

Sears also cites historical evidence for his claims. He states that Americans have been told about the virtues of a low fat diet for the past 20 years, and yet remain the fattest people in the world. He concludes from this that low fat diets do not work. He does not ask the obvious question, however, if Americans actually have a low fat diet. The answer is no, Americans have a relatively high fat diet and eat fewer carbohydrates than most other nations, despite popular nutritional advice to the contrary. 4,2 This completely contradicts Sears’s claims for the Zone, but he ignores this simple fact.

Sears also cites the research of others in his defense. He reports the results of a 1990 study by researchers at Ohio State University in which the endurance of swimmers on an 80% carbohydrate diet were compared to those on a 40% carbohydrate diet. (pg.49) He attempts to debunk the concept that high carbohydrate diets are helpful to athletes by reporting that the 80% group had no advantage over the 40% group. He fails to observe, however, that the zone favorable diet is also contradicted by the fact that the 40% group had no advantage over the 80% group. The fact is, the two groups showed no difference, with the most economical conclusion that macronutrient balance is not critical to athletic performance.

More amazing than the treatment by Sears of studies and research are the claims that he unabashedly makes for his new diet. Beyond weight loss and improved athletic performance, he also claims that living “in the zone” will reduce heart disease, reduce cancer risk, improve overall health, decrease infections – by beefing up the magic bullet of modern medical pseudoscience, the immune system – improve mental capacity, offer hope to AIDS victims, ameliorate chronic illnesses such as MS and arthritis, relieve chronic fatigue, and even achieve the holy grail of medicine, prolonged life. This list should sound familiar to anyone aquainted with the claims of almost any form of alternative medicine.

He compares his claims to an exaggeratedly pessimistic view of more conventional approaches to these diseases. He falsely claims, for instance, that no significant advances have been made in cancer treatment, despite the fact that survival rates for many cancers have increased steadily over the past few decades. He also falsely claims that there is only one drug to treat AIDS, AZT. Apparently he is unaware of newer drugs, such as didanosine or zalcitabine5, or the fact that AIDS survival has been steadily improving. Sears suffers from the common misconception that finding a total cure for such diseases is the only measure of success.

The examples stated above are representative of the sloppy, biased, and unscientific style Sears uses to support the zone as a breakthrough in nutritional science. It is very telling that Sears does not have a single scientific reference in a 272 page book (including appendices) discussing an alleged scientific breakthrough. His discussion of research is designed to confuse and distort the process of science. He ignores alternative explanations and contradictory research, and he leaps to unjustified conclusions.

The unfortunate power of Sears’s book stems in part from the fact that Sears, as a PhD, is familiar enough with the trappings of science to cloak his work in the appearance of legitimate science. His pseudoscientific claims are intricately interwoven with legitimate and accepted facts of basic human physiology (a half-truth is the worst possible kind of lie). It is not likely that a lay audience will be able to pick out the good science from the bad.

One must also consider Sears’s choice in publishing his theories in the format of a self-help book (actually two books, with the follow up Mastering The Zone), rather than in the peer-reviewed scientific literature. His work would never survive such a rigorous and necessarily unforgiving forum. Besides, why should he take the chance that careful research will prove his ideas to be wrong, when simply presenting them to the public, untested and unproven, will garner mountainous profits? Sears has published only one brief paper on the subject, in the Journal of the Massachusetts Dental Society.6 Hardly the “Nobel prize winning research” which the book jacket proclaims.

In fairness, the Zone does have some virtues when compared to many of its predecessors. For one, it is probably not harmful. Although lack of harm is a small virtue indeed when compared to the monumental claims touted in this book. It also does not rely upon a monotonous diet of one kind of food, and therefore can be well balanced in the conventional sense. Sears even includes a chapter advocating exercise in combination with diet control, but he does state that exercise alone is not very beneficial, unless of course one is exercising in the Zone.

It is difficult to say, as with many such pseudoscientific claims, if Sears is simply an incompetent and irresponsible scientist, working outside of his field of training, or if his work is the result of a premeditated attempt at amassing profits through popular deception. I can only observe that if I had intended to craft a work with the optimal balance of scientific terms, amazing claims, and popular appeal in order to maximize profits, I could hardly have created a better work than Enter the Zone.


1. Byers T: Dietary Trends in the United States, Relevance to Cancer Preven tion. Cancer, 72(3):1015-1018, 1993
2. Posner BM: Secular trends in diet and risk factors for cardiovascular disease: The Framingham Study. Journal of the American Dietetic Association, 95(2):171-179, 1995
3. Barret S, Jarvis WT: The Health Robbers. Prometheus Books, 1993
4. Stephen AM: Intake of carbohydrate and its components – international comparisons, trends over time, and effects of changing to low-fat diets. American Journal of Clinical Nutrition, 62: 851S-867S, 1995
5. Crowe S: Managing HIV. Medical Journal of Australia, 164:2909-295, 1996
6. Sears B: Build a diet for life with fat. Journal of the Massachusetts Dental Society, 42(4):204-205, 1993