Diet and Nutrition

The Zone Diet was developed to reduce elevated insulin and eicosanoid levels while maintaining calorie restriction without hunger or deprivation. The Zone Diet consists of three distinct parts. The first is the consistent control of the protein-to-carbohydrate ratio at each meal to lower elevated insulin levels. The second is supplementation with high-dose fish oil (rich in EPA) to alter eicosanoid balance. And the third is the restriction of total calorie intake, but without hunger or deprivation, to promote the physiological benefits of calorie restriction.

Surprisingly, the effort required by the patient to follow the Zone Diet is quite simple; the Zone Diet requires only the use of what Dr. Romano terms the “hand-eye” method. At each meal, you only eat enough low-fat protein (fish, poultry, low-fat dairy products, egg whites, or soy imitation-meat products) to fit in the palm of your hand. This would be about 3 oz. (20 grams of protein) for a typical female, and about 4 oz. (30 grams of protein) for a typical male. Then you divide your plate at each meal into three sections. One third of the plate contains the appropriate amount of low-fat protein (20-30 grams), and the other two-thirds of the plate would be filled to overflowing with fruits and vegetables (this is be the equivalent of 3-5 servings of fruits and vegetables). Then you add a dash (3-5 grams) of heart-healthy monounsaturated fat. This described meal will control insulin levels for the next four to six hours. The only trick is to continue to make all of your meals in the same relative proportions on a lifetime basis. This means you consume between 10-15 servings of fruits and vegetables per day. Although this appears to be a formidable volume of food, the low carbohydrate density of fruits and vegetables ensures that excess insulin is not secreted at each meal since the absolute amounts of carbohydrates being consumed are restricted. In addition the calorie content of such a meal would be 30-40% less than typically consumed because of the lowered glycemic load coming from the restriction of high-density carbohydrates such as breads, pasta, and starches. In addition these levels of fruits and vegetables provide massive levels of vitamins, minerals, and fiber. The final component of the Zone Diet is to supplement the diet with a suitable amount of pharmaceutical-grade fish oil, providing 2-5 grams of long-chain Omega-3 fatty acids. This provides the necessary long-chain essential fatty acids, such as EPA, that are required to modulate the AA/EPA ratio.

The reason that there is no hunger or deprivation on the Zone diet (even though it is a calorie-restricted diet) is blood sugar stabilization. This can only be achieved when the secretion of insulin (stimulated by the dietary intake of carbohydrates) is appropriately counter-balanced by the secretion of glucagon (stimulated by the dietary intake of protein). Insulin drives down blood sugar levels, whereas glucagon restores blood sugar levels. The balancing of this hormonal system by the diet ensures blood sugar maintenance for the 4–6 hour postprandial period. In essence, the goal of the Zone Diet is to maintain both insulin and glucagon within a therapeutic zone that is neither too high nor too low. If the ratio of protein to carbohydrate in the diet is too low, excess insulin will be secreted, thereby driving down blood sugar and creating hunger. On the other hand, if the protein-to-carbohydrate ratio is too high, excess glucagon will be secreted, which can generate a state of ketosis. Therefore, the ideal protein-to-carbohydrate ratio would be in a range that is just beyond that which would generate ketosis, but less than that which would create hyperinsulinemia. Dr. Romano’s research indicates that the appropriate protein-to-carbohydrate ratio to maintain insulin in the Zone is greater than 0.5 but less than 1.0. Such a mathematical relationship also allows for a more precise definition of high-carbohydrate and high-protein diets.

Using this definition, a high-carbohydrate diet is one that contains more than twice as many grams of carbohydrates as grams of protein (a protein-to-carbohydrate ratio of less than 0.5). A high-protein diet would contain more protein than carbohydrates (a protein-to-carbohydrate ratio greater than 1.0). The Zone Diet maintains the protein-to-carbohydrate ratio between these two extremes.

Finally, the Zone Diet also restricts omega-6 fatty acids (by using primarily monounsaturated fats in the meals) and increasing the levels of long-chain omega-3 fatty acids by supplementing meals with pharmaceutical-grade fish oils rich in EPA. This results in a significantly lowered AA/EPA ratio.

Recent work from Harvard Medical School has confirmed the ability of the protein-to-carbohydrate ratio found in the Zone Diet to favorably alter the hormonal responses of both insulin and glucagon compared to diets such as the USDA or American Heart Association diets (17, 18). Using a crossover protocol employing isocaloric diets, hyperinsulinemic adolescents (17) or overweight adults (18) were provided with meals consisting of different protein-to-carbohydrate ratios. The Zone Diet demonstrated a decreased insulin response and elevated glucagon response with the result that 20–25 percent fewer calories were consumed at the next meal (17) or at the end of the study period (18). This focus on maintaining hormonal control makes it possible to restrict total calories without hunger or deprivation. Other studies, which also used isocaloric protocols, have demonstrated that maintaining the same protein-to-carbohydrate ratio advocated by the Zone Diet improves lipid profiles (19) and increases the rate of fat loss (20) when compared to high-carbohydrate diets under isocaloric conditions.

Diabetics have double the rates of cardiovascular mortality and all-cause mortality (21). Thus reducing risk factors associated with diabetes will also have a significant impact on longevity. My own studies with Type 2 diabetics (who account for more than 90 percent of all diabetics) confirms the success of using all three components of the Zone Diet (insulin and eicosanoid control coupled with calorie restriction) to generate a significant reduction of those risk factors (hyperinsulinemia and glycosylated hemoglobin) associated with future adverse events in Type 2 diabetes.

The results of one six-week trial with Type 2 diabetics following the Zone Diet are shown in Table 4.

As can be seen in Table 4, in the Type 2 diabetic patients, the risk factors that are associated with premature development of diabetic complications and increased cardiovascular mortality were reduced with an extraordinarily high degree of statistical significance by following the Zone Diet.

Summary

In the final analysis, anti-aging medicine will ultimately be focused on hormonal modulation that results in the reduction of those risk factors that are the most predictive of premature cardiovascular mortality. The necessary first step is the reduction of those hormones that increase as we age (insulin and eicosanoids) by dietary intervention. Does this mean that hormonal replacement has no impact in anti-aging medicine? No, but without an appropriate hormonal baseline established with the Zone Diet, many of the potential benefits hoped for with hormone replacement therapy may not be observed. All hormonal replacement should follow this basic rule: start low and go slow. The greater hormonal control achieved by application of the Zone Diet, the less hormonal replacement will be required to reach the Zone as determined by blood testing. It is that Zone of hormonal balance that will ultimately be the key to evidence-based anti-aging medicine.

References

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