Health Psychology Home Page
Papers written by students providing scientific reviews of topics related to health and well being
|Search||Home | Weight Loss | Alternative Therapy | Supplements | Eating Disorders | Fitness | Links | Self-Assessment | About this Page ||
High-protein/ low-carbohydrate diets are nothing new to Americans these days; they seem overwhelmingly to be the most popular among those people trying to lose weight. Ph.D. Dr. Barry Searsí books on his version of the high-protein diet, the Zone Diet, are among the best selling diet books on the market. The diet seems to be yielding quick and noticeable results to those who follow Dr. Searsí plan. Many people are desperate to lose weight and have tried numerous methods that have not produced sufficient and long lasting results. This could perhaps be the reason for the recent craze for the high-protein/ low-carbohydrate diet- it really does cause weight loss. Even Hollywood movie stars such as actresses Jennifer Anniston and Sandra Bullock attribute their recent weight loss and improvement in appearance to the Zone diet. However, in the midst of all of the hype, we must examine the claims and assess the degree to which this diet is indeed effective. Further, considering that Dr. Searsí advice contradicts what we have been told for years about dieting, we must determine if it is healthy. Could we have been misinformed when given advice to eat a diet rich in carbohydrates, or is this diet another that falls short of what it promises?
TABLE OF CONTENTS:
Does the Zone Diet work?
-Problems With The Zone
-Problems With The Zone
|Related Research Studies|
- Click Here to learn more About the ZONE Diet on the Web
THE ZONE AND ITíS PURPOSE
Dr. Barry Sears, Ph.D., is responsible for the development of The Zone nutrition concept, which is based upon 15 years of his research in the field of bio-nutrition. It was guided by the same science that won the 1982 Nobel Prize for Medicine dealing with the research of eicosanoids. The term "Zone" is an expression used by athletes to describe a near-euphoric state of maximum physical, mental and psychological performance (http://www.nutritionsciencenews.com/NSN_backs/Jan_97/zonediet.html). The purpose of Dr. Searsí Zone is not only to lose weight, but also to reach what Dr. Barry Sears refers to as "SuperHealth." According to Dr. Sears, author of Enter the Zone and Mastering the Zone, a #1 New York Times Best Seller, "SuperHealth is a permanently enhanced quality of life: looking better, feeling better, strengthening the immune system, and slowing down the physiological aging process. And SuperHealth is a state that everyone can achieve." The goal of the Zone is to achieve a metabolic state of optimal health where your body works at peak efficiency. To achieve this, the idea of the Zone is to use combinations of certain foods to control specific hormones in your body.
THE ZONE GUIDELINES
The Zone promises to make you think clearly, lose weight more efficiently (and keep it off), have more energy and vitality, and to make you look and feel better. However, according to Dr. Sears, to achieve this state of being you must follow certain guidelines when choosing which foods to eat. One of the most important ideas of the Zone diet is to balance the amount of carbohydrates and proteins that you consume. The diet recommends that you keep three food groups: carbohydrates, proteins, and fats in the ratio of 40:30:30 respectively. However, it is important not only to eat meals in this ratio, but also to eat favorable foods in each group. For instance, favorable proteins include fish, chicken, turkey breast, egg whites, and low-fat cottage cheese, while unfavorable proteins would be such foods as red meat and organ meats. Favorable Carbohydrates include vegetables, fruits, oatmeal, and whole wheat bread. Unfavorable carbohydrates are such foods as dry breakfast cereal, pastas and white bread. Lastly, when considering the fat component to your Zone-favorable meal you should add something like olive oil, light mayonnaise or avocado rather than butter or margarine. Additionally, Dr. Sears recommends that you eat these balanced, zone-favorable meals frequently, never going more than 4 or 5 hours without eating. Following these guidelines, you will essentially have "entered the Zone" and apparently be on your way to losing weight and optimizing your physical and mental state.
For more information on the Zone plan guidelines and how to calculate personal Zone dietary requirements go tohttp://www.ne.net/~zone/primer
HOW IT CLAIMS TO WORK
Dr. Sears claims that the reason that this diet works is because it manipulates insulin levels and avoids eicosanoid imbalances. Living in "the Zone" essentially means using food as a drug to acquire an adequate and beneficial hormonal balance with insulin, glucagon, and eicosanoids. Concerning insulin, Sears claims that a high-carbohydrate, low-fat meal triggers an excess release of insulin, and more insulin means more stored body fat. He says that by controlling the protein to carbohydrate ratio, you can keep insulin levels in balance because the protein counteracts the carbohydrates you eat. Dr. Sears says that insulin, not fat, that is the enemy and that it is an excess of this hormone that makes you fat and keeps you fat because it is a storage hormone for turning excess carbohydrates into fat. Insulin and glucagon hormones regulate glucose, which provides fuel for the mind and the body. . Insulin lowers blood sugar levels while glucagon raises them. When there is too much glucose, the extra glucose is then stored as fat. Searsí contention on eicosanoids is that they control this hormonal system. Eicosanoids, Sears says, are the super-hormones of the body and virtually every disease is the result of an imbalance of these hormones. Further, he claims that his recommended ratio of protein to carbohydrate along with fat will ensure balance in these crucial hormones (http://www.drmcdougall.com/debate.html). . Fatty acids are the chemical building blocks of these Zone-crucial eicosanoids and consequently, Zone favorable meals require that a small portion of monounsaturated fat be added (which are eicosanoid-neutral). He looks at food as a way to regulate the eicosanoids produced in the body that control the amount and balance of other released hormones. This is the way he claims to ensure weight loss through balancing hormones, specifically eicosanoids.
says that there are also many other benefits of a Zone-favorable diet. The Zone claims to aid in the prevention and treatment of many diseases and disorders. Some of these include hypothyroidism, type (I) and (II) diabetes, heart disease, PMS, chronic fatigue, depression, cancer. Further, there have been claims that the Zone helps alleviate the painful symptoms of multiple sclerosis and HIV (http://www.healthworks2000.com/zone_basics2.htm). The Zone also has seemingly amazing effects on common conditions such as asthma and allergies according to a one Dr. Kahl in a web article about the Zone benefits beyond weight loss. He strongly believes that the ability effectively to control certain hormones through the right combinations of foods is extremely advantageous with the prevention and treatment of certain disorders. Patients of his would, after being on the Zone diet for a significant period of time, report that in addition to weight loss or decrease in blood pressure, they no longer needed their inhalers or allergy medicines. All this from changing their diet. Additionally, Dr. Kahl asserts that if you suffer from asthma, food or seasonal allergies, or chronic pain, the Zone diet will most of the time relieve your symptoms (http://www.zoneperfect.com/List_of_Articles.asp). Many of those that have been on the Zone diet have cited these claims and many more besides just weight loss.
DOES THE ZONE DIET WORK?
Undoubtedly, there are numerous claims that the Zone is indeed effective. However, the claims that Dr. Sears makes are derived from his personal medical research- none of which is published in medical journals, make his assertions questionable to critics. The fact that Americans are getting fatter although fat consumption is down supports Searsí claims. When considering the claims he makes, there are many testimonials to support them from various ranges of people. Athletes, doctors, and everyday people seem to have reaped benefits from this diet in varying degrees. Athletes have tried to improve their quality of performance and contemporary doctors have claimed to have found a new way of life by entering the Zone. One such doctor is Dr. Deborah Chud who not only follows the Zone diet, but also has created an extensive cookbook filled with delicious Zone favorable meals that Dr. Sears himself has used. She says, "Öthe Zone has totally revolutionized my thinking about health, diet and nutrition. Thatís a lot coming from a physician (http://www.zoneperfect.com/Deborah%20Chud%20part%202.html)." She claims what many people are slowly finding out for themselves, that apparently high carbohydrate and low-fat diets were not working. She was experiencing weight gain and a lack of energy. Further, she had chronic upper body pain that hindered her from her favorite activities. However, after a couple of months in the Zone, she reported a loss 25 pounds, pain alleviation to a small extent and a noticeable increase in energy level.
PROBLEMS WITH THE ZONE
With all the claims that Dr. Sears makes and all the attention that this diet has gotten recently, you may wonder why you should not jump into this diet right away! There are results are significant for weight loss and there are many assertions that the diet improves various other aspects of life. However, in the midst of all the hype and excitement, we shouldnít accept a diet blindly without looking at it thoroughly to make sure that the information is correct and the method of losing weight a healthy and smart choice not just considering short term, but also long term results.
One significant downfall of Dr. Searsí diet plan is that he has no published medical research (i.e.- in medical journals) to support his claims concerning his diet. The success stories that we find are all testimonials, lacking the concrete medical research that the diet is as wonderful as Dr. Searsí claims that it is. He tested his theories on many subjects suffering from such things as: heart disease, diabetes, obesity, AIDS, and autoimmune disorders. Based on his own findings, he draws conclusions that our health can be greatly improved by the Zone, but the studies have yet to show up in medical journals.
Although Searsí Zone includes many carbohydrates such as fruits and vegetables, some critics have called his diet irresponsible and carbo-phobic. Sears even admits that if the bottom half of the Food Guide Pyramid was eliminated, what would be left is a Zone-favorable diet. Like most high-protein diets, the Zone is somewhat anti-carbohydrate because of what it claims they do to insulin levels. However, this claim becomes questionable when we examine an Asian diet which is highly carbohydrate-rich consisting of lots of noodles, rice, grains, as well as vegetables and fruits. In China, rates of chronic disease are generally lower than those in the United States. In a study at Cornell University, it was found that the Chinese consume 20 percent more calories than Americans yet weigh 20 percent less than Americans (http://www.nutritionsciencenews.com/NSN_backs/Jan_97/zonediet.html). The fact is that if meals are moderate in size, you will only produce a moderate amount of insulin and that the purpose of insulin is not to store fat, but to help metabolize carbohydrates. Therefore, if you eat a carbohydrate-rich meal, as the Asians tend to do, the concentration of insulin will fall shortly after helping metabolize the carbohydrates.
leaves room for speculation. Many protein-rich foods are very high in fat and cholesterol and many times contain chemicals with vitamin and mineral imbalances. Such organizations as the American Heart Association and the American Cancer Society recommend that you eat less animal products and more plant foods. They believe that chronic illnesses are caused by unhealthy diets and that improved health would come from eating less animal product and more plant foods. Further, protein-rich foods such as meats and dairy products are known to cause obesity and heart diseases and numerous other studied ailments (http://www.drmcdougall.com/debate.html). Additionally, excessive protein may cause damage in many ways. Because protein is metabolized by the liver and excreted by the kidneys, excessive protein causes damage to these organs. Additionally, it can cause metabolic changes that cause bone loss and kidney stones. When you overload on protein, the acid that it produces has to be neutralized and that is when the bones start to disintegrate and this leads to osteoporosis. In these ways, the high-protein consumption can be detrimental to your health.
RELATED RESEARCH STUDIES
There has been little research concerning the Zone diet itself, but many done on high-protein/ low-carbohydrate diets and their effectiveness as well as their healthiness. Here are a few articles that provide more scientific insight as to the credibility of what Dr. Sears claims about the Zone.
(1) The article "High-meat diets and cancer risk" by Sheila Bingham in 1999 provides information about the correlation between high protein consumption and the risks associated with certain cancers. Bingham reports that around 80% of prostate, bowel and breast cancers are related to dietary practices, especially meat consumption. The cohort studies cited in this article showed that red and processed meats more than white meats were apparently related to the risk of colon cancer although the quantitative amounts of meat consumed were not reported. A possible explanation of the reason of increased risks of cancer is what happens when the meat is cooked. For example, NH3 and N-nitroso compounds which form from residues of bacteria in the large bowel are adversely affected by the amines that are produced when cooking meat, causing mutations similar to those that occur in colo-rectal cancer. The most relevant argument of the article concerning the Zone, however, is the fact that increasing the amount of carbohydrates does not have an effect on the NH3 and N-nitroso compounds output. This does not agree with the claim that balancing the amount of carbohydrates and proteins in the zone result in optimal health. The contention at the end of the article by the Current Department of Health (1998) is that meat consumption should not rise and that we should consider a reduction of intake, which is in direct contrast to Dr. Barry Searsí claims about the Zone.
(2) The study entitled "Randomized trial on protein vs carbohydrate in ad libitum fat reduced diet for the treatment of obesity" in 1999 concluded findings that indeed supported Searsí claim concerning increased dietary protein. Although the study proved that the increase in protein was beneficial, it was purely in the context of weight loss. The objective was to study the effect of replacement of carbohydrates with protein with respect to weight loss. It was a randomized 6-month study with three groups: the high carbohydrate group, the high protein group, and the control group with no change in diet. The subjects were 65 healthy as well as obese and overweight people between 18 and 55. The outcome was that the high protein group lost more weight than the high carbohydrate group and the control group experienced no weight loss. This clinical trial indeed supports Searsí claims in that it showed that replacement of some carbohydrate with protein in the diet increases the amount of weight loss.
(3) The 1997 article "High-oil compared with low-fat, high carbohydrate diets in the prevention of ischemic heart disease" by Katan provides some support to Searsí claims when it studies the risks of heart disease associated with fat. The statement is made that saturated fatty acids do indeed increase the risk of heart disease, however, the article says that it is not all fats that are responsible for this. The article review two kinds of reduced saturated fat diets: the high carbohydrate and low-density lipoprotein and the high density lipoprotein. The weight loss of the high carbohydrate diet was fairly small and didnít help the ratio of high density lipoproteins to low density while the diet high in unsaturated fats improved the ratio. The article concludes that recommending no fats is too vague and that unsaturated fats could possibly be not as bad as once thought. However, it is agreed that saturated fats are detrimental concerning heart disease risks.
(4) Searsí claims that athletes perform better when in the Zone are put to the test in the 1999 article "Physical exercise as a modulator adaptation to low and high carbohydrate and low and high fat intakes." This article shows that carbohydrates are essential for optimal performance by an athlete, particularly at intensities above 65%. It claims that during rigorous activity, the energy is supplied from carbohydrates or glycogen while at lower intensity workouts the energy can come from fats. The main point becomes that high carbohydrate intake improves performance of high intensities. Further, it goes as far to say that exercise ability is lessened with a high fat diet and that muscle protein synthesis is stimulated more after exercise with sufficient carbohydrate intake. The fact that this article asserts that consuming fats instead of carbohydrates lessens the performance of a competitive athlete contrasts Searsí claim about optimal athletic performance when in the Zone because the diet sacrifices carbohydrates.
(5) The article "Does carbohydrate-rich, protein-poor food prevent a deterioration of mood and cognitive performance of stress-prone subjects when subjected to a stressful task?" in 1998 provides information about mental health in relation to diet that contradicts Sears. While Sears claims that the Zone diet ensures peak mental efficiency, this article contends with a study that concludes that a diet rich in proteins caused a decline in vigor and a rise in stress-induced depression. The study consisted of 24 subjects with high stress proneness and 24 with low. The experiment was with uncontrollable stress situations under the high carbohydrate diet and some under the high protein diet. The study also surveyed the levels of tryptophan and serotonin levels with respect to the individual diets. The conclusion of this study was that a carbohydrate rich diet in high stress people would probably cause more self control probably due to increased levels of serotonin and tryptophan.
It is very easy to get caught up in all the hype these days with wonder diets and drugs that claim to make you lose weight fast and many times the claims are untrue. Despite the fact that this Zone diet does indeed seem to be getting people the results that they have yearned for in a weight loss program, the overall healthiness of the diet must always be considered. It seems as though the high protein diet would be a good choice if you were severely obese because individuals under the program do experience significant weight loss. However, the long term effects of the diet concerning, for example, protein damage and bone loss, do not seem worth while. The findings of this new diet craze remain poorly researched and until the such people as Dr. Sears can get some of their research in medical journals that we can trust are true, my contention is to stick with a balanced diet and exercise to lose weight.
RESOURCES USED(By number in the Related Research Studies above)
The Health Psychology Home Page is
produced and maintained by David Schlundt, PhD.
Vanderbilt Homepage | Introduction to Vanderbilt | Admissions | Colleges & Schools | Research Centers | News & Media Information | People at Vanderbilt | Libraries | Administrative Departments | Medical
|Return to the Health Psychology Home Page|
|Send E-mail comments or questions to Dr. Schlundt|