Prior to the publication of THE ZONE, Americans (and so that part of the world paying attention) were in the grip of the advice first given by Nathan Pritikin and later enshrined by the USDA food charts.

Eat lots of grains, vegetables and fruit. Only a little meat and dairy products. Fear fat. Fear cholesterol.

Fat made you fat/ And cholesterol stuck to the walls of your arteries and gave you heart attacks.

The "No Cholesterol" label was used to sell bread, even though bread never contained any cholesterol.

Dr. Sears' major finding was that food is not just a container for vitamins, minerals and calories -- as important as those are -- but a powerful "drug" which affects the balance of our important hormones, especially insulin and glucagon.

The effects of this drug on our bodies is determined by the macronutrients -- carbohydrates, protein and fat.

We need all three, but in the proper balance. When we eat too much or too little of one or more of them, it creates a hormonal response that greatly affects whether our bodies store or burn fat.

When Nathan Pritikin, Dean Ornish and the United States Department of Agriculture put the fear of saturated fat and cholesterol into Americans, they drove millions to eat more grains-based foods.

Whole grain breads and pasta became hip. After all, Americans don't want to eat fruit and vegetables. If you can't have a good steak, spaghetti tastes good.

Dr. Sears was not the first to point out the dangers of this overconsumption of carbohydrates. Dr. Atkins did that years before. However, the Atkins "solution" was to give up all carbohydrates. Our bodies need carbohydrates. We're not built to live on meat, eggs and cheese alone. Therefore, while people can and do lose weight on the Atkins diet, few people can stay on it in the long run.

Although the Zone diet is often lumped together with the Atkins diet by people who don't honestly compare them, Barry Sears is just as critical of overconsuming protein.

He agrees that saturated fats are not healthy, and advocates eating monosaturated fats whenever possible. (Found in avocados, olive oil and nuts, especially macadamia).

The "Zone" is when your body's hormones, and therefore its metabolism and overall health, are in their proper ranges.

Using scientific research and studies done on the diet of primitive people (past and present), he determined that our bodies our genetically programmed to thrive on a balance of 30% protein, 30% fat and 40% carbohydrates.

This make intuitive sense when you remember that, except for the past 10,000 years since agriculture was discovered, the human species ate primarily: lean meat from wild animals, insects, bird eggs, leaves, roots, and fruit (in season).

Dr. Sears took the basic elements of this paleolithic diet and adapted it for modern Americans facing food choices our ancestors could not have dreamed of: hamburgers, pizzas, bread, rice, soft drinks and candy.

Most of THE ZONE is taken up with explaining the scientific basis for how and why this modernized form of the prehistoric diet can help us lose weight and regain optimum health.

In fact, this book was often criticized as too technical and scientific. Dr. Sears now says it was intended to explain the Zone diet to doctors. He didn't realize it would be read by so many average layman.

He's written many books since then. They focus on popularising the Zone by explaining it in less technical language, updating it with new scientific findings, and putting new spins on the concept so that each new book is worth reading and finds a new audience.

Therefore, everyone who has learned about the Zone from later books should also grab hold of a copy of this book. Unless you're a doctor or medical researcher you won't understand it all, but reading it will reinforce Dr. Sears' credibility.

More than any other "diet" author, it's obvious he knows his stuff.