From: Jerry Vonderharr <vonder@netonecom.net>

Subject: Zone diet

The July/August issue of the Nutrition Action Health Letter published an

article by Bonnie Liebman entitled "Carbo-Phobia," in which she

critiques the concept of the Zone Diet. What follows is a response by

Dr. Barry Sears to that article.

Mr. Michael Jacobson

Center for Science in the Public Interest

1875 Connecticut Avenue

NW Suite 30

Washington, D.C. 20059

Dear Mr. Jacobson:

I have had the opportunity to review Ms. Bonnie Liebman's article

entitled "Carbo-phobia" in your July/August 1996 issue of the Nutrition

Action Health Letter. I find it unfortunate that your readers were

subjected to a great number of scientific inaccuracies by Ms. Liebman.

It is obvious in her article that she missed the entire point of my

book, The Zone, which argues that the key to health is maintaining

insulin within a relatively narrow zone: not too high, not too low. If

Ms. Liebman had paid any attention to the book, she would have realized

that my recommended dietary program has no similarity to the

high-protein, ketogenic diets of the 1970s. Nor is it a "diet," as it is

clear it represents a life-long hormonal control program for maintenance

of insulin levels. Nonetheless, let me comment on each of Ms. Liebman's

critiques of my statements in The Zone.

Claim One: Americans are fatter because they eat less fat.

Ms. Liebman forgot to complete the statement, "and more carbohydrates."

Fat as a percentage of calories in the American diet has dropped

dramatically over the past 15 years, which has been followed by an

epidemic rise in obesity that is still accelerating 1. The U.S.

Department of Agriculture (USDA) has stated that fat consumption in the

late 1970s was approximately 85 grams per day. In 1994, the average fat

consumption as determined by the USDA was approximately 73 grams of fat

per day. This represents a 14% decrease in total fat consumption. This

decrease in total fat is difficult to reconcile with the 31% increase in

obesity. Even using Ms. Liebman's contention that fat consumption has

not changed, it is clear that the total increase in calories (100-300

per day) is coming purely from carbohydrates. The central theme of The

Zone is that excessive consumption of carbohydrates causes an increase

in insulin, which in turns increases fat accumulation. I consider the

increase of 25 to 75 grams of carbohydrate per day to be excessive.

Ms. Liebman simply forgets that the best way to fatten cattle is to feed

them excessive amounts of low-fat grain. Likewise the best way to fatten

humans is to feed them excessive amounts of low-fat grain, but now in

the form of bagels and pasta. Ms. Liebman should be aware that pasta

consumption has increased 115% in the last decade. 2

Claim Two: Carbohydrates cause obesity.

Again Ms. Liebman has missed the central focus of The Zone, which is

insulin control. It is excess insulin that makes you fat. Fat has no

effect on insulin, protein has a slight effect, but carbohydrates have a

powerful stimulatory effect on insulin. Insulin is a storage hormone

that drives fat, protein, and carbohydrate to their respective storage

sites, and prevents their release for energy. In particular, insulin

inhibits the activity of the hormone-sensitive lipase of the adipose

tissue that allows the release of stored body fat for energy.

There are two dietary methods to increase insulin. One is to eat too

many carbohydrates, and the other is to eat too many calories containing

protein and carbohydrate (fat has no effect on insulin). When you do

both, as do most Americans, you have a sure-fire prescription for fat

accumulation.

Ms Liebman quotes Dr. Gerald Reaven who states that "a calorie is a

calorie is a calorie." I agree with that statement. Unfortunately the

hormonal effect of a calorie of carbohydrate is different than the

hormonal effect of a calorie of protein which is different than the

hormonal effect of a calorie of fat. Then she quotes a study done by Dr.

Reaven 3 which shows that two different 1,000 per day calorie diets

produced the same fat loss in metabolic ward patients. What she failed

to tell the readers is that one diet was a ketogenic diet (15%

carbohydrate and 53% fat) and the other was basically a Zone Diet (45%

carbohydrate, 26% fat, 29% protein). In both diets, insulin levels were

lowered. It is only when you lower insulin levels that you can access

stored body fat. If Ms. Liebman had read the article carefully, she

would have discovered the following statement:

Consumption of low-fat, high-carbohydrate diets for weight maintenance

advocated by the National Cholesterol Education Program seems to

minimize the fall in plasma insulin and triacylglycerol concentrations.

This is most likely related to previous results showing that both plasma

insulin and triglacylglycerol concentrations increase in proportion to

dietary carbohydrate consumption.

If you don't decrease insulin levels, then it impossible to lose excess

body fat. The authors further state:

"Although it is often suggested that low-fat diets will have a better

long-term benefit with a weight-maintenance diet, we are unaware of

persuasive data in support of this view."

If Ms. Liebman had made a careful survey of the literature she would

have found a classic study published in Lancet nearly 40 years ago that

compared weight loss in overweight individuals on different 1,000

calorie per day diets under hospital ward conditions. On diets composed

of 90% of calories as fat, the patients lost approximately one pound of

weight per day. On 90% protein, the patients lost approximately 0.6

pounds of weight per day. Obviously, neither of these diets is

realistic. Using a mixed diet with 42% of the calories as carbohydrates

(basically the Zone Diet), the patients lost approximately 0.4 pounds

per day. And what about a 1,000 calorie per day diet consisting of 90%

carbohydrates. The patients actually gained weight 4.

When asked if he were appointed Nutrition Czar of America what level of

carbohydrates he would recommend to the general public, Dr. Reaven

himself states in an interview in the Townsend Letter for Doctors 5 that

it would be "Probably something like 45%."

In the same interview when Dr. Reaven was asked "Do you think that the

current high-carbohydrate craze is the wrong prescription for the

America public?" his answer was the following: "Yes, I feel very

strongly about that. I've published many papers suggesting that."

Obviously, Ms. Liebman never read any of those papers. Like Dr. Reaven,

I agree that a high-carbohydrate diet is not the appropriate diet for

the American public.

But at least Ms. Liebman agrees that high insulin levels raise the risk

of heart disease 6. That was the reason I developed the Zone Diet in

order to lower insulin levels, and maintain insulin in a specified

therapeutic zone on a life-time basis. To my knowledge the only drug

that lowers insulin levels is called food, assuming it has the correct

macronutrient composition.

Claim Three. Calories don't count ... protein does.

Ms. Liebman's writing gets a little confusing here since she spends her

time talking about eicosanoids. So for the benefit of her readers, let

me explain her opening statement, and then discuss eicosanoids.

Protein does count. No one should ever consume more protein than the

body needs. But conversely, one should never consume less. That is

equivalent to protein malnutrition. The Zone Diet is based upon a

protein- adequate diet individualized to a person's unique needs. Simply

stated: one size does not fit all. Once an individual's daily protein

intake that maintains his or her lean body mass is calculated, that

amount of protein is then spread throughout the day in three meals and

two snacks. The amount of protein at each meal or snack dictates how

much carbohydrate and fat should be consumed at the same time to

maintain insulin in a relatively tight zone; not too high, not too low.

This is why the Zone Diet has no similarity to high-protein diets, which

encourage an over-consumption of protein, and consequently an

over-consumption of fat.

Fat has been made to be the dietary villain of the last 15 years. Fat

has no effect on insulin. Only carbohydrate and protein will effect its

production. The goal of the Zone Diet is to keep insulin in a zone, so

that its anabolic properties to drive macronutrients to the appropriate

storage sites are maintained, but its inhibitory properties on the

release of stored fat in the adipose tissue and stored carbohydrate in

the liver are minimized. If you can access stored fat (a virtually

unlimited source of energy) by keeping insulin in that zone, you don't

need to consume excessive amounts of incoming calories. By releasing

stored carbohydrate from the liver you maintain adequate blood sugar

levels for optimal brain function.

Obviously, you can only access stored body fat for so long until you

reach your optimal per cent body fat. Once a person reaches that point,

they will need to start adding more monounsaturated fat (which has no

effect on insulin) to their diet as a caloric ballast to maintain their

body fat in a desired zone.

The Zone Diet is designed to allow you to tap into hormonal control

systems that have been invariant for the past 40 million years.

Controlling the incoming balance of protein, carbohydrate, and fat

allows a person to achieve hormonal balance. Calories don't count, but

hormonal balance does.

Now let me discuss eicosanoids. To the best of my knowledge, the 1982

Noble Prize in Medicine which was awarded for understanding the

importance of eicosanoids, has not been rescinded. Ms. Liebman quotes

Dr. Reaven stating that "I am unaware of any evidence that changes in

insulin have an effect on eicosanoids." Although Dr. Reaven is a leading

authority on insulin resistance and the medical consequences of

hyperinsulinemia, he is undoubtedly unaware of a large body of data that

demonstrates that elevated levels of insulin increase the production of

arachidonic acid, the building block of "bad" eicosanoids 7,8. And for

the opinion that eicosanoids have no effect on a variety of disease

states, I refer Ms. Liebman to a 22-volume set of books entitled

Advances in Prostaglandin, Thromboxane, and Leukotriene Research

published by Raven Press.

It is also difficult for me to understand Ms. Liebman's statement that

no evidence exists "that eating equal amounts of protein and

carbohydrate at every meal lowers insulin levels" when she quoted a

study by Reaven that shows that the protein-to-carbohydrate ratio does

have a major effect on insulin levels 9. That study published in the

American Journal of Clinical Nutrition studied the effects of an

isocaloric diet when each meal was controlled with the same

macronutrient ratio in overweight, hyperinsulinemic individuals. A ratio

of protein-to- carbohydrate of 2.13 lowered insulin levels by 46% in six

weeks whereas a protein-to-carbohydrate ratio of 0.63 lowered insulin

levels by 8% in six weeks. The Zone Diet strives to keep the

protein-to-carbohydrate ratio near 0.75. Therefore based on Dr. Reaven's

own published studies, one would expect insulin levels to be lowered

between 8 and 46% on the Zone Diet. I suggest that Ms. Liebman actually

read the articles that she quotes in her criticism.

I am likewise surprised by Dr. Reaven's quote that "no one has ever

studied" the effect of the protein-to-carbohydrate ratio on insulin

levels when he was a co-author of such a published study 10.

Another article quoted by Ms. Liebman demonstrated that high insulin

levels poses a risk for developing cardiovascular disease. That same

study showed that lowering insulin levels by 18% is sufficient to

prevent the development of coronary artery disease 11. Since Dr.

Reaven's published research has demonstrated that controlling the

protein-to- carbohydrate ratio can lower insulin 12, I am sure that he

would recommend an insulin-lowering diet for preventing cardiovascular

disease development. That is exactly what the Zone Diet is.

In fact, other studies published by Dr. Reaven have shown in Type II

diabetics (who are characterized by producing too much insulin) that

their condition can be remarkably improved by decreasing carbohydrate

and replacing it with monounsaturated fat 13,14. Again that sounds very

close to the Zone Diet.

In summary, Ms. Liebman has done a great disservice to your readers by

not understanding the contents of my book, in addition to having not

carefully read the papers she so eagerly quotes to "justify" her

preconceived notions about what constitutes a "healthy" diet. The Zone

Diet is based upon thinking of the hormonal consequences of food, which

is very different than thinking about the caloric effects of food. Ms.

Liebman has failed to grasp that basic concept.

Sincerely yours,

<Picture>

Barry Sears, Ph.D.

President

Eicotech Corporation

------------------------------------------------------------------------

References

1Alfred JB. "Too much of a good thing." J Am Dietetic Assoc 95: 417-420

(1995)

2USDA. Research News. January 16, 1996

3Golay A, Allaz A-F, Morel Y, de Tonnac N, Tankova S, and Reaven G.

"Similar weight loss with low- or high-carbohydrate diets." Am J Clin

Nutr 63: 174-178 (1996)

4Kekwick A and Pawan GLS. "Calorie intake in relation to body-weight

changes in the obese." Lancet ii: 155-161 (1956)

5"Interview with Dr. Gerald Reaven" Townsend Letter Doctors.

August/September pp. 128--129 (1995)

6Depres J-P, Lamarche B, Mauriege P, Cantin B, Dagenais GR, Moorjani S,

and Lujpien P-J. "Hyperinsulinemia as an independent risk factor for

ischemic heart disease." N Engl J Med 334: 952-957 (1996)

7Brenner RR. "Nutritional and hormonal factors influencing desaturation

of essential fatty acids." Prog Lipid Res 20: 41-47 (1982)

8Pelikanova T, Kohout M, Base J, Stefka Z, Kovar J, Kazdova L, and Valek

J. "Effect of acute hyperinsulinemia on fatty acid composition of serum

lipids in non-insulin-dependent diabetics and health men." Clinica

Chimica Acta 203: 329-338 (1991)

9Golay et al. 174-178.

10Golay et al. 174-178.

11Depres et al. 952-957.

12Golay A et al. 174-178.

13Garg A, Bantle JP, Henry RR, Coulston AM, Griver KA, Raatz SK,

Brinkley L, Chen YD, Grundy SM, Huet BA, and Reaven GM. "Effects of

varying carbohydrate content of diet in patients with non-insulin

dependent diabetes mellitus." JAMA 271: 1421-1428 (1994)

14Chen YI, Coulston AM, Zhou M, Hollenbeck CB, and Reaven GM. "Why do

low-fat high-carbohydrate diets accentuate postprandial lipemia in

patients with NIDDM?" Diabetes Care 18: 10-16 (1995)