Weight Loss Articles

The concept of “the Zone” is that food should be treated like a prescription drug that is designed to promote the desired hormonal response throughout the day. The hormones in question are insulin, glucagon, and eicosanoids. Insulin and glucagon are well-known hormones, and their functions are described accurately.

The goal of Zone dieting is to eat the correct balance of carbohydrates and protein so that glucagon is produced instead of insulin because glucagon promotes the formation of “good” eicosanoids while insulin promotes the formation of “bad” eicosanoids that cause all sorts of diseases.

To reach the Zone, one must consume foods in a protein-to-carbohydrate ratio of 0.75, which is 3 grams of protein for every 4 grams of carbohydrate, at every meal and snack, and without allowing more than 5 hours between meals or snacks. The author converts grams into blocks of protein and carbohydrate and provides food lists and meal plans for these.

Protein requirements in the Zone are based on lean body mass and level of physical activity (the same method that is used in Protein Power). The lean body mass is calculated using standardized charts that use height, hip, and abdomen measurements in women and weight, wrist, and waist measurements in men.

The calculated protein requirement is not to be exceeded and is to be spread throughout the day, to avoid increased insulin levels caused by protein digestion. Therefore, a person would end up with a calorie limit on their total daily intake, since protein has a maximum value, and carbohydrate and fat intake are measured by protein intake. Zone dieting claims to improve numerous health conditions, primarily based on eicosanoid activities.

Scientific Analysis

The entire design of the Zone diet lacks scientific evidence to support it. The concept is correct that providing higher levels of carbohydrates would avoid ketosis, which is a condition that may be hazardous over the long term. However, because of a restriction on the intake of protein, carbohydrates, and fat, it is likely that insufficient calories and carbohydrates will be available for most people to avoid ketosis. In other words, the ketosis that results from starvation – getting too few calories to meet basic needs – can easily occur in many persons based on their calculations for daily intakes. There may also not be enough protein in the diet to prevent loss of muscle mass.

Dieticians’ research on protein requirements didn’t indicate valid evidence for using activity level as a basis for protein intake. In the absence of glucose, the muscles use fat for energy and do not need more or less protein for activity. When protein is “broken down” to provide fuel, the actual molecules are conserved while the bonds between them are broken. To restore the protein molecules only energy is required to reform the chemical bonds.

An additional consideration is that a person’s protein requirements depend on what other nutrients are consumed as energy sources. When carbohydrates are restricted in the diet, more protein is needed to be converted to glucose as fuel for the brain. If the protein requirement is increased and allowed consumption above the minimum level, then the ratio of carbohydrate to protein would be too high for many persons to avoid excess insulin production. Excess protein in any meal can cause excess insulin and cause the protein to be stored as fat is without scientific evidence.

There are scientific errors in the Zone that it becomes very complicated to describe them all – but then again the Zone formula is extremely complicated.

1) Scientific evidence shows that the total amount of protein should not be restricted, which the Zone does.

2) The Zone’s calculation of protein intake is based on lean body mass and activity level which is scientifically invalid and will restrict protein intake too much for almost everyone who is limiting carbohydrate in the diet.

3) Carbohydrate intake is tied to protein intake, so it varies for different people in the Zone diet. There is no scientific basis for this since all persons have the same baseline glucose requirement of approximately 120 grams daily for brain activity. With the Zone calculations, persons who have low protein calculations will likely not get enough carbohydrates to inhibit ketosis, while those with high protein calculations may get more than the ideal amount.

4) Fat intake is based on the protein intake calculation and restricted to that amount. If this calculation is low, it removes the body’s natural appetite control system that is stimulated by fat. According to scientific evidence, fat should not be restricted in the diet.

Here are some examples to illustrate:

A 150-pound woman who is sedentary and overweight calculates her body fat at 33%. Her Zone protein requirement comes out to 60 grams. Her Zone carbohydrate portion is 80 grams daily, which may be too low to inhibit ketosis. Her fat portion is 13 grams. Her total daily calorie intake is 677 calories, which is extremely low. If we even consider that her protein foods will include about 1/3 fat and add another 180 calories, she is still getting only 857 calories daily. Not only will she have to be in ketosis to supply her baseline energy needs, but she will also lose muscle mass due to low protein intake.

When compared to a 150-pound world-class athlete who has 21% body fat and is extremely active. Even though her weight is the same, her body fat and activity level give her a protein portion of 186 grams daily, 3 times that of the sedentary woman! She also will get 153 grams of carbohydrate, which she will probably “burn” as fuel, and 26 grams of fat. With an additional 1/3 of her protein foods considered as fat, she gets 1682 calories daily. On days she is extremely active, she probably will experience ketosis for many hours of the day despite the high protein intake, because her total calories are restricted. She may even lose muscle mass since her intake of fat for fuel is restricted. On days when she is less active, she will probably have to dispose of a large portion of her protein and will experience moderate insulin levels due to the high carbohydrate intake.

It is easy to see why the Zone diet has worked in athletes because they are probably getting close to their protein and energy needs.

One issue not brought up by the Zone diet is that of cholesterol levels. All of the low carb diet plans should improve cholesterol levels, except possibly for this one. Scientific evidence shows us why consuming fewer carbohydrates should cause LDL or “bad” cholesterol to decrease. In the Zone, the level of carbohydrates consumed may not be low enough to achieve this, especially for someone who has a large lean body mass and, therefore, a high calculated carbohydrate intake. Additionally, fat in the diet has been shown to increase HDL or “good” cholesterol, and saturated fat promotes the greatest increase. The Zone diet not only limits fat intake but also advises against the use of saturated fat.

As for eicosanoids, whether or not the control of eicosanoid production by specific nutrient intake provides all the effects he claims is not at all scientifically proven. In fact, if the protein intake were unlimited, as it should be, using the Zone ratio of carbohydrate to protein at each meal would probably stimulate insulin and “bad” eicosanoids in most persons.