The Zone

What It Is

What is The Zone? Besides being the title of a mega-seller diet book, the Zone is a place where we find ourselves "feeling alert, refreshed, and full of energy," according to author Barry Sears, PhD. Sears, a former researcher in bio technology at the Massachusetts Institute of Technology, and the book's co-author Bill Lawren maintain that life in the Zone is what wellness is all about.

Like other popular diet books, The Zone offers more than just weight-loss claims. By retooling your metabolism with a diet that is 30% protein, 30% fat, and 40% carbohydrates, The Zone contends that you can expect to turn back encroaching heart disease, high blood pressure, and diabetes. Another much-touted advantage is better athletic performance. Sears doesn't come right out and claim he has found the cure for heart disease or diabetes, or how to win athletic competitions, but instead he provides glowing anecdotes from people who have taken The Zone to heart.

What The Zone does boldly claim is that much of the current thinking about good nutrition -- a diet high in carbohydrates, low in protein, and fats -- is "dead wrong." What's more, Sears contends, that type of diet has contributed to our risk of contracting serious, even life-threatening ailments such as heart disease, diabetes, and possibly cancer.

As a former scientist, Sears devotes considerable time to discussion of the science on which he based his theory. Put simply, the Zone is a "metabolic state in which the body works at peak efficiency," and that state is created by eating a set ratio of carbohydrates, protein, and fat.

What You Can Eat

The Zone does not recommend that you eat fewer calories than you're currently consuming, just different ones. Although the book has a more complicated and exacting measurement of what to eat, it can be simplified as:

A small amount of protein at every meal (approximately the size of your palm or one small chicken breast) and at every snack (one in the late afternoon, one in the late evening) "Favorable" carbohydrates twice the size of the protein portion -- these include most vegetables and lentils, beans, whole grains, and most fruits A smaller amount of carbohydrates if you have chosen "unfavorable" ones -- these include brown rice, pasta, papaya, mango, banana, dry breakfast cereal, bread, bagel, tortilla, carrots, and all fruit juices. Dairy products are not verboten, but The Zone devotes little time to them, except to explain how quickly they release glucose. Sears prefers egg whites and egg substitutes to whole eggs, and low-fat or no-fat cheeses and milk.

The diet keeps saturated fats to a minimum but includes olive, canola, macadamia nuts, and avocados. Certain unfavorable carbohydrates are restricted because they release glucose quickly: grains, breads, pasta, rice, and other similar starches, a deviation from conventional definitions of a good diet. Overall, the diet is higher in protein and fat than traditional diets, which would have us eat nearly three-quarters of all calories as carbohydrates.

Sears is fairly rigid about the amount of protein/fat/carbohydrate each of us needs, and takes the reader through a short course in determining our protein need, based on size, age, and activity, which then determines the amount of fats and carbohydrates we should be eating.

Happily for those of us who would be depressed at the thought of forgoing deserts for the rest of our lives, his list of allowable foods includes, among others, high-fat ice cream. Why high-fat? Because the fat retards the rate of absorption of carbohydrate into the body, according to Sears. Alas, the recommended portion is a mere half-cup.

How It Works

The Zone's eating plan is a combination of a small amount of low-fat protein at every meal, fats, and carbohydrates in the form of fiber-rich vegetables and fruits. The plan establishes a ratio for which Sears contends the body is genetically programmed (that 40-30-30 figure). And yes, we'll be thinner to boot.

Sears claims that the diet is based on his 15 years of research in bio nutrition. Although the book is full of success stories, including those of elite athletes, research that validates his specific claims isn't there. That doesn't mean that Sears' theories are wrong; it's just that no scientific evidence has proven that his program works.

Sears bases his theory on using diet to control the body's production of the hormone insulin. Among insulin's many roles, it helps regulate storage of excess energy as fat. The goal is to keep a balance between fat-storing insulin and the hormone glucagon, insulin's opposite, whose job it is to release the stored glucose from the liver when it is needed. Maintaining the correct balance between the two is accomplished by watching the size and specific content of your meals. In other words, you must be mindful of what you put on your plate. Sears suggests that we think of food not as "a source of calories but as a control system for hormones."

What the Experts Say

The Zone draws mixed reviews from nutrition experts. Researchers at the Center for Science in the Public Interest, which rated several fad diets, recently put it on their acceptable list, unlike Dr. Atkins' New Diet Revolution, Sugar Busters!, The Carbohydrate Addict's Diet, and Protein Power. "If you ignore the scientific rhetoric, the diet isn't bad," says Bonnie Liebman, MS, nutrition director for the center's publication, Nutrition Action Healthletter. As a caveat, she points out the diet restricts carbohydrates more than necessary. "You are getting carbohydrates from fruit and vegetables on the diet, but a lot of the science is bunk," she says. What she likes is that the diet is relatively easy to follow: "You have a piece of protein the size of your palm, and you fill the rest of your plate up with fruits and vegetables."


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Susan Roberts, PhD, head of the Weight Regulation Program at Tufts University and a professor of medicine and psychiatry there, also gives The Zone a qualified thumbs up. "Like most fad diet books, The Zone takes one of the several known controllers of energy, blood glucose, and blows it up into a whole book," she says. "It downplays the other factors that also determine how hungry we get and how much we eat, such as fiber and the caloric density of the food."

Roberts also finds fault with some of The Zone's food recommendations, such as that high-fat ice cream. Sears says it's OK, because it won't raise your blood sugar precipitously, but it's not OK for other reasons, Roberts notes, such as the fact that the cream in the ice cream is saturated fat, which isn't good for your overall cholesterol. (To be fair to the diet, Sears only allows a half-cup and certainly doesn't suggest you make it a habit.) Yet Roberts likes the amount of vegetables and legumes recommended, and so, she says, "My personal rating for The Zone would be three stars out of five."

Other nutritional experts, including some of Sears' former colleagues, are critical of his conclusions from the scientific evidence, contending that he has distorted or exaggerated the meaning of much of the basic research. They point out that no direct studies to verify his conclusions have been performed.

Food for Thought

The 40-30-30 ratio applies to all meals all the time, and a broad range of foods are allowed, so there are no confusing schedules or conditions that need to be memorized. Though dieters should find it easy to follow, nutritionists give the diet mixed reviews.

Reviewed By Charlotte E. Grayson, MD February 2004.

SOURCES: Sears, B. The Zone, 1995, Regan Books. Bonnie Liebman, MS, nutrition director, The Center for Science in the Public Interest. Susan Roberts, PhD, director of the Weight Regulation Program, Tufts University. Boston.

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Last Editorial Review: 5/25/2005