The Zone diet is a diet popularized in books by Barry Sears. It advocates "hormonal thinking" instead of caloric thinking as an approach to eating. It is not a weight-loss "diet" (though it can be used quite successfully for that purpose); rather it is a way of eating — the intake of food that produces the best results within our bodies based on a hypothesis of how the human body has evolved to cope with the food intake throughout history.
The Zone is Sears's term for proper hormone balance. When insulin levels are neither too high nor too low, the human body is not busy storing excess calories as fat which means that those stores are available when needed. The human body cannot store fat and burn fat at the same time, and it takes time (significant time if insulin levels were high because of unbalanced eating) to switch from the former to the latter. Using stored fat for energy causes weight loss. The diet centers on a "40:30:30" ratio of calories obtained daily from carbohydrates, proteins, and fats, respectively. The exact formula is always under debate, but studies over the past several years (including a non-scientific study by Scientific American Frontiers) have shown that it can produce weight loss at reasonable rates.
Sears emphasizes a hormonal paradox which "low-fat" advocates were unaware of, namely that low-fat diets increase the production of the hormone insulin, causing the body to store more fat. He points to the cattle ranching practice of fattening livestock efficiently by feeding them lots of low-fat grain. He and others have noted the irony that human diets in the West for the last twenty years have been full of low-fat carbohydrates, yet people are more obese — Sears claims as a result. The zone diet is the most important diet in america because of its ability to control blood sugar and newly discovered hormones called "eicosanoids".
In addition to this, Sears describes fat consumption as essential for "burning" fat. Monounsaturated fats in a meal contribute to a feeling of fullness and modulate the rate at which carbohydrates are absorbed into the bloodstream. Slower carbohydrate absorption means lower insulin levels which means less stored fat and faster transition to burning fat. If the body needs energy and can't burn fat because of high insulin levels, a person feels tired as their brain starves and metabolism slows to compensate. Such a condition is also a leading cause of cravings for a chocolate bar or other high-carb snacks (which just starts the high-insulin cycle all over again).
The "low-carb craze"
Low-carbohydrate diets like the Atkins diet became extremely popular throughout the United States in 2003 and 2004, but Sears claims that they miss the point. According to him, they ignore the importance of hormonal balance, as well as the influence of dietary balance on digestion and hormone production. In addition, high-protein/low-carb diets cause the production of some "bad" hormones that the body tries to flush from the system. Much of the initial weight-loss from such diets is water loss.
The Zone in Italy
In Italy the Zone has been "translated" by Gigliola Braga, a biologist who applied Sears' method to the local food and habits.
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