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It seems like everywhere you look these days there is some new diet
plan making miraculous promises of weight loss through pills, plans, and
formulas. The zone diet seems to have become America's latest diet craze.
The zone diet was developed by Dr. Barry Sears in his book," Enter
the Zone" which was on the bestseller lists for weeks. The zone promises
high energy, weight loss, and no hunger to those willing to follow the
simple set of zone rules. It sounds great you say, but does it really work?
The "zone" was first referred to by athletes as a period of
maximum performance and energy levels. When things are clicking and every
part of our body is working at its best, we say we are "in the zone."
When we fall short we experience a loss of performance, more illness, and
feel moody and restless. The zone diet helps individuals to stay in the
zone, not just trying to hit or miss. Instead of experiencing periodic
energy highs and lows, it regulates levels throughout the day, putting
the body in a metabolic state of peak efficiency.
Much of this energy regulation is controlled by eicosanoids (http://www.coolrunning.com/sponsor/thezone/zone.htm#eicos).
These are some of the most important chemical messengers in the body. However,
since they perform their cell-to-cell communications very rapidly and in
very small concentrations, they have often been overlooked by many researchers.
Eicosanoids are completely derived from dietary fat. In addition, they
have opposing physiological functions, which can be either good or bad.
The good eicosanoids accelerate the use of stored body fat, whereas the
bad do the opposite. These levels of eicosanoids can be controlled by what
we eat at each meal. For example, high levels of carbohydrates decrease
the production of good eicosanoids and increase the production of bad eicosanoids.
So to sumrnarize, the protein/carbohydrate balance in our diet controls
the insulin/glucagon balance in our bodies which effects eicosanoid production.
Barry Sears claims that by following the zone guidelines, our bodies are
able to produce the optimal level of good eicosanoids and reduce the production
of bad ones.
Here are some of the zone guidelines:
Eat enough protein for your body's needs, no more, no less. This amount is determined by your amount of lean body mass ( http://www.Eicotech.com/calculator/default.html ) and your activity level.
At every meal eat protein and carbohydrates in the ratio of three parts protein to four parts carbohydrate.
As much as possible, eat carbohydrates with a low glycemic index (This list includes most fiuits and vegetables).
Eat sufficient amounts of fat to control the rate of digestion of the meal and to control hunger. Usually, this is about 30% of the calories in the meal.
Drink at least eight glasses of water or sugar-free decaffeinated beverages a day.
As much as possible, eat protein with low levels of saturated fat such as fish, chicken, turkey, tofu, egg whites, and low-fat dairy products.
As much as possible, eat monounsaturated fats in preference to saturated fats.
Never go more than five hours without eating a zone-favorable meal or snack. Eat within one hour of waking and have a snack before workouts and before bedtime.
food is ever completely banned, but some must be eaten in moderation.
Additional information is available to calculate protein, carbohytkate, andfat blocks in accordance with Barry Sears' formulations at
The zone works because of the influence which insulin (http://www.users.cts.com/crash/d/dbrowndc/zone.htm)
plays in ourbodies. Like the zone diet, most low carbohydrate diets work
because they control the production of insulin. The digestive system treats
all carbohydrates the same, as if they were glucose sugar. Glucose causes
the pancreas to pump out insulin into the blood. It causes the muscles,
liver, and fat cells to store away as much glucose as they can, burn the
remaining carbohydrates, and save the dietary fat for later use.
This causes several problems. First, in the presence of large amounts
of carbohydrates, insulin causes the cells to reduce fat burning and to
bum carbohydrates instead. Second, insulin has a long half-life in our
bloodstream. The half-life is longer than it takes the body to store away
the glucose. This causes us to run out of blood sugar and to get tired
Therefore, the zone diet recommends that for the maximum control of
insulin, the gram ratio of carbohydrates to protein to fat should be 9:7:3.
Under the zone diet, this ratio is considered a "block of food."
In addition, almost equal calories should come from each group.
In addition to having higher energy levels, the zone promises many other
additional health benefits. Here are a few:
Better athletic performance
Better concentration and moods # Loss of food cravings
Weight loss/ better fitting clothes
Better health with less illness
trained to bum fat for fuel
A related benefit is cited by Dr. Brown (http://www.user.cts.com/crash/d/dbrowndc/zone.htm).
He points out that years of excessive insulin stimulation eventually bums
out the cell's insulin receptors so that it takes more insulin to react
normally. This "insulin resistance" can lead to hyperinsulinemia.
Excessive amounts of insulin have been linked to many serious health
problems. It stimulates the growth of the muscle lining in arteries, which
causes the arteries to harden. Insulin also signals the kidneys to retain
salt which increases hypertension. Finally, insulin stimulates cholesterol
synthesis which can lead to heart disease.
Although the benefits seem unbelievable many people support the zone
One of the most popular forms of support for the zone diet is through testimonials.
Unfortunately, this is one of the least valid forms of support. Nevertheless
numerous people have posted "Zone Luck" testimonials on the Zone
Home web page. The testimonials range from losing six pounds to losing
over fifty pounds. They also claim that the zone has helped them give up
coffee, exercise more, and stop needing to take diabetic medication. In
addition, one woman claims that the zone diet has given her daughter with
Attention Deficit Disorder the increased ability to attend to tasks.
Another zone testimony is offered by Dr. Brown, a chiropractor from
San Diego. He created his own web page (http://www.users.cts.conVcrash/d/dbrowndc/zone.htm)
to discuss his personal success with the zone diet and to discuss the basic
mechanics of the plan. However, at the end of his web page, Dr. Brown conveniently
offers his own services for consultations concerning the zone diet. He
asks that you leave your credit card number and states that consultations
will cost .50 per minute with a thirty-five dollar minimum.
Finally, Professor Mchael G. Kurilla, states in a document discussing
protein requirement, that he agrees with most of the zone diets' advice.
"One the whole, I agree with most of his general advice and rationale
underlying the diet plan, 1) adequate protein intake, 2) reduction of carbohydrate
intake, 3) favoring of low GI carbohydrates, 4) reduction of saturated
fats, 5) increase in monounsaturated fats, etc. These are the core of the
diet plan and are all clearly rooted in sound nutritional advice. "(Kurilla,
It appears that most of the Zone's claims about eicosanoids are accurate
concerning their relation to the immune system.
In a study by Gray and Martinovic (I994), researchers examined the relationship
between the functions of eicosanoids and the immune system. They hypothesized
that changes in the ratio of essential fatty acids are the normal physiological
responses to stressors, but when stress is prolonged or excessive, the
essential fatty acid metabolites may become unpredictably hyporesponsive.
Reviews of chronic fatigue syndrome show hyper and hypo-responsiveness
in immune function. The study found that dietary essential fatty acid modulation
can alter ratios of both membrane essential fatty acids and produced essential
fatty acid metabolites.
Suchner and Senftleben (I 994) conducted a similar study. Their objective
was to review the range of action of polyunsaturated fatty acids on the
basis of interactions with eicosanoids- Their results concluded that polyunsaturated
fatty acids are the precursors of eicosanoid formation. In addition, that
interactions between polyunsaturated fatty acids and the immune system
are influenced by the rate of synthesis as well as by the efficacy of various
Although research supports some of the Zone's dietary-recommendations,
much of the data is contradictory.
A recent statement concerning the dietary guidelines recommended by
the American Heart Association both agrees and disagrees with some of the
Zone's rules. The points they agree on are 30% of the day's total caloric
intake should come from fat and that individuals should restrict their
intake of saturated fats. However, there is a large discrepancy between
their daily recommendations concerning carbohydrates and protein. Whereas
the Zone recommends only 40% of daily caloric intake come from carbohydrates,
the American Heart Association recommends 55-60%. This leaves a remaining
30% of calories from protein under the Zone diet and 10-15% under the American
Heart Association guidelines. (American Heart Association, 1994).
Current research indicates that some of the Zone's advice concerning
low carbohydrate intake may be inaccurate.
Shah, McGovern, French, and Bamer (1994) conducted a study which compared
the effect of a low-fat, ad libitum, complex-carbohydrate (LFAL) diet with
a low-energy (LE) diet on weight loss over a six month period in moderately
obese women. Their findings conflict with the Zone's recommendations that
a low carbohydrate diet is ideal. The researchers concluded that an LFAL
diet can result in substantial weight loss and is associated with improved
palatability and quality of life in comparison to a LE diet.
Finally, the Zone's claims that it helps diminishfood cravings is
not supported by current research.
In their study, Harvey, Wing and Mullen (I 993) compared the changes
in self-reported cravings experienced by 93 obese individuals with Type
II diabetes who were randomly assigned to treatment programs. One group
ate a balanced, low-calorie diet of 1000- 1200 kcal/day, with all foods
allowed in moderation. The other group ate a very low calorie diet where
intake was restricted to 400 kcal/day with only lean meat, fish, or fowl
allowed. The results found that there were significant decreases in cravings
for all types of foods over the twenty weeks of the study for both conditions.
Therefore, the particular types of foods which were eaten did not affect
the loss of food cravings.
In addition to research reviews, other specialists offer their concerns
about the zone diet:
Endocrinologist Joe Barrera agrees with some aspects of the diet. However,
he feels the problem lies in the reconnnendation that instead of carbohydrates
we need to eat more protein. Barrera believes that the actual amounts should
lie somewhere in the middle.
Likewise, nutritionalist Debra Waterhouse has some problems with the
zone diet's advice. The zone diet specifies that sugar is not allowed.
Waterhouse feels that if a person tries to completely remove sugar from
their diet, they are not likely to stick to the diet for long.
Finally, Michael Kurilla attempts to disseminate several of the negative
claims made against high protein diets in an article he wrote. Some of
the claims against proteins are as follows: 1) That individuals with certain
forms of renal disease can slow progression with a low protein diet. 2)
Research indicates that low protein diets may prevent osteoporosis. 3)
That low protein diets appear to extend lifespan.
The current body of information available seems to be inadequate to
assess the effectiveness and safety of the zone diet plan. However, there
seems to be general agreement that the basic guidelines offer sound nutritional
advice. In addition, the weight loss claims of sheading about one pound
a week appear to be reasonable. The main controversy seems to be over the
body's daily requirements for fat and protein. Furthermore, each of the
zone web pages included disclaimers advising that individuals should consuft
their physician before starting the zone diet. For these reasons, the Zone
diet seems to be an effective diet option for some people but not for everyone.
American Heart Association. Dietary guidelines for healthy American
adults: a statement for physicians and health professionals by the Nutrition
Committee. Circulation. 1988; 7: 72 1 A724A.
Barrera, J. and Waterhouse, D. (1996). The Zone Diet Book. News Center
Gray, J., and Martinovic, A. (I 994). Eicosanoids and essential fatty
acid modulation in chronic disease and the chronic fatigue syndrome, Medical
Hypotheses, 43(l): 31-42.
Harvey, J., Wing, R.,& Mullen, M. (I 993). Effects on food cravings
of a very low calorie diet or a balanced, low calorie diet. Appetite, 21(2):
Kurilla, Michael G. (I 996). Protein Requirements in Humans. Intemet
Shah, M., McGovern, P., French, S. & Baxter J. (1994). Comparison
of a low-fat, ad libitum complex-carbohydrate diet with a low-energy diet
in moderately obese women. American Journal of Clinical Nutrition, 59(5):
Suchner, U., and Senftleben, U. (1994). h=une modulation by polyunsaturated
fatty acids during nutritional therapy: interactions with synthesis and
effects of eicosanoids. Infusionstherapie und Transfusionsmedzin, 21(3):
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