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The zone diet explained
by Barry Sears
One of the problems of being an innovator is that you are often misunderstood-even by those who portend to imitate your work. Nowhere is this more true than with the Zone Diet. I developed the Zone Diet to treat cardiovascular patients by keeping the levels of the hormone insulin in a tight zone: not too high, not too low. The magic elixir to achieve this hormonal goal: food.
Although developed for cardiovascular patients, I did much of the early testing of the Zone Diet with elite athletes, in particular with elite swimmers at Stanford University. Why? Because athletic performance is also enhanced by keeping insulin in a tight zone. The early results of that work were reported in SWIM Magazine (title, date) and Swimming World (title, date) nearly four years ago-the first national magazines to offer a serious discussion of my work. Since that time, Stanford University has won eight of the last 10 NCAA Championships [note: update to include 1997 results] and swimmers that I have personally worked with have won 17 gold medals in the past two Olympics. Coincidence? Perhaps, but then you can always ask the Stanford coaches how important is the role that diet plays in their programs.
The key to understanding the Zone Diet is to think hormonally, not calorically. By this I mean that the hormonal effect of a calorie of carbohydrate is different than the hormonal effect of a calorie of protein, which is still different than the hormonal effect of a calorie of fat. It's the complex interplay of these hormonal responses that controls your human physiology.
Caloric thinking tries to describe the number of calories you need and what the "ideal" percentage of calories coming from carbohydrate is to make you perform better. This is why I cringe when I hear the Zone Diet described as a "40-30-30" diet: 40% carbohydrate, 30% protein and 30% fat. The Zone Diet has nothing to do with the percentages of calories. It has everything to do with the absolute amount of protein you eat (see Table 1), and therefore the carbohydrate and fat required at every meal to get the best "hormonal bang for the buck." In fact, for many elite athletes, the largest percentage of their calories will actually come from fat, not carbohydrate.
Many critics of the Zone Diet also have never grasped the basic concepts of hormonal control inherent in the program. Yet I am still waiting for the first study to show eating a high carbohydrate diet for more than seven days will improve athletic performance in any athlete. Why am I waiting? Because no such studies exist1-3. In fact, for elite swimmers, one study demonstrated that eating a high-carbohydrate diet for more than seven days only increases their levels of lactic acid build-up during workouts1. Hardly a ringing endorsement for the high carbohydrate conventional wisdom. In addition, when elite athletes are fed a higher fat, lower carbohydrate diet, performance improves dramatically.
Furthermore, statements that "a calorie is calorie" are hard to understand in light of recently published research that shows that when elite runners eat up to 1000 extra calories of fat per day, it has no effect on their weight or their percent body fat. Did these extra fat calories simply disappear, or did this happen because fat has no effect on insulin? However, this massive amount of extra fat did have a favorable effect on their blood lipid profiles5. As stated by the authors of this study, a "low-fat diet partially reduces the beneficial effect endurance training confers.5" Isn't this a good description of many of the readers of this magazine?
What are we to make of published research that says eating a high-carbohydrate diet doesn't improve athletic performance, or that eating a low-fat diet may have dangerous cardiovascular implications for active athletes? I think it means we had better start thinking of food in a different way if you want better athletic performance or better health. I personally believe we should be thinking of food hormonally, not calorically. There are no good diets or bad diets, only hormonally correct diets. What is a hormonally correct diet? One that keeps insulin in a tight zone; not too high, not too low. It's a matter of balance. What I have tried to present in my books, The Zone and Mastering the Zone is such a hormonal perspective.
How can you tell if your diet is hormonally correct? If you are losing excess body fat, you maintain peak mental acuity throughout the day, and you are rarely hungry, then your diet is hormonically correct. But in the final analysis, your blood will tell you. Your blood has no political agenda, your blood tells you whether you're naughty or nice. Measure your fasting blood insulin levels, your ratio of triglycerides to HDL cholesterol and your glycosylated hemoglobin (all of these are standard tests), and then check them every three months. If the levels are continually decreasing, then your diet is hormonally correct. If they are rising, then your diet is hormonally incorrect. And if your diet is hormonally incorrect, then make some simple adjustments in the ratio of protein to carbohydrate in your diet (like adjusting a carburetor of a car), until your blood (and your daily performance in and out of the pool) tells you your diet is hormonally correct.
There is no question that athletic activity like swimming will not only improve the quality of your life, but the extent of your life6. What I argue for is to make your diet work with your exercise program, not against it. And since hormones are the most powerful drugs known to medical science, it only makes sense to use the most powerful drug we have-food-to alter and control their levels. That is the basis of the Zone Diet. But you have to know the hormonal rules about food, which are very different than the caloric rules. You have to eat: just eat wisely.
In the final analysis, the Zone Diet is what your grandmother told you to eat. What did she say? Eat small meals throughout the day, always have some protein at every meal, always eat your fruits and vegetables, and take your cod liver oil. Laugh as you may, she was right on target hormonally. The Zone Diet is simply explaining what your grandmother knew intuitively was correct, and putting in terms of 21st century biotechnology.
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