Zone diet
The Zone diet is a diet popularized in books by Barry Sears. It advocates balancing protein and carbohydrate in 3:4 ratios. It is not primarily a weight-loss "diet", though it can be used quite successfully for that purpose .

# 'The Zone'
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 the PBS documentary show Scientific American Frontiers) have shown that it can produce weight loss at reasonable rates. The Scientific American Frontiers study compared the effectiveness of several popular 'diet' regimes including the Zone; somewhat to the surprise of the show's staff, the participants on the Zone experienced the greatest fat loss while simultaneously gaining muscle mass. Participants also reported the Zone as the easiest regime to adjust to, i.e. having the fewest adverse affects such as fatigue or hunger.
"The Zone" is Sears' term for proper hormone balance. When insulin levels are neither too high nor too low, and glucagon levels are not too high, then specific anti-inflammatory chemicals (types of eicosanoids) are released, which have similar effects to aspirin, but without downsides such as gastric bleeding. Sears claims that a 30:40 ratio of protein to carbohydrates triggers this effect, and this is called 'The Zone.' Sears claims that these natural anti-inflammatories are heart and health friendly.
Additionally, the human body in caloric balance is more efficient and does not have to store excess calories as fat. The human body cannot store fat and burn fat at the same time, and Sears believes 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.
Another key feature of the Zone diet, introduced in his later books, is an intake of the proper ratio of Omega-3 to Omega-6 fatty acids. Dr. Sears is believed to have popularized the taking of pharmaceutical grade Omega 3 fish oils.

# Hormonal paradoxes
Sears emphasizes a hormonal paradox of which "low-fat" advocates were unaware, 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.
Additionally, Sears describes fat consumption as essential for "burning" fat. Monounsaturated fats in a meal contribute to a feeling of fullness and decreases the rate at which carbohydrates are absorbed into the bloodstream.  Slower carbohydrate absorption means lower insulin levels which means less stored fat and a faster transition to fat burning.  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.  This occurs because the brain runs on glucose and high insulin levels deplete blood glucose levels. Such condition, rebound hypoglycemia causes sweet cravings (which just starts the high-insulin cycle all over again).
Sears describes a Zone meal as follows: Eat as much protein as the palm of your hand, as much nonstarchy raw vegetables as you can stand for the vitamins, enough carbohydrates to maintain mental clarity because the brain runs on glucose, and enough monounsaturated oils to keep feelings of hunger away.

# The Zone and low-carb diets
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.

# The Zone in Italy
The introduction of the Zone in Italy began in 1997 by a physician, Aronne Romano M.D. who applied this nutritional style to patients and athletes. Since the 2nd edition of the book "Come Raggiungere la Zona" (The Zone), in 1999, the Chef Memo Romano and his brother Aronne modified the original recipes and menu to suit the local food and habits.  The diffusion of the Zone continues with the efforts of many people including Paolo Perucci, Gigliola Braga, Simone Masci and Daniela Morandi.

# Famous obesity case
Possibly the most famous case of someone using the diet effectively has been Mexican Manuel Uribe. After weighing in at around 560 kg (1234 lbs or over 88 stone) but within a year had lost about 180 kg..

# Criticism
The American Heart Association does not recommend the Zone Diet due to high-protein, lack of essential nutrients and little information on long-term effects. It should be noted that AMA's  characterization of the Zone diet as 'high-protein' is false, or at least a serious exaggeration, given that 70% of the calories in the Zone diet come from non-protein sources(i.e. carbohydrates, 40%, and fats 30%). The Zone does not emphasize an increase of protein intake in the standard American diet, but rather, a reduction in the intake of unhealthy carbohydrates (i.e. refined breads, starches, sugars, etc.) and an increase in healthy carbohydrates from high-fiber vegetables and fruits and healthy monounsaturated fats.
A vegetarian diet, according to Sears, is as far as you can get from The Zone. Individuals who promote a vegetarian diet are critical of Zone and similar diets.

# "Zone" books by Sears
(Partial list)
- Sears, Barry (1995). The Zone: A Dietary Road Map. HarperCollins Publishers. ISBN 0060987065..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"\"""\"""'""'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{display:none;font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em} Sears's initial book on the Zone diet.
- Sears, Barry (1997). Mastering the Zone. HarperCollins Publishers. ISBN 006101124X. Sears urges substitution of raw vegetables for pastas, breads and refined sugars. More diagrams and flowcharts than in The Zone.
- Sears, Barry (1999). The Anti-Aging Zone. Regan Books. ISBN 0060392436. Information on meditation, relaxation and exercise in addition to diet.
- Sears, Barry (2000). A Week in the Zone: A Quick Course in the Healthiest Diet for You. Regan Books. ISBN 0060741902. Unknown parameter |coauthors= ignored (help)
- Sears, Barry (2000). The Soy Zone. Regan Books. ISBN 0060393106. Discusses Sears preference for soy protein as part of his balanced eating program. "The longest-living people in the world" living in Okinawa, Japan consume much greater amounts of soy protein and eat smaller meals than most other people.
- Sears, Barry (2002). The Omega Rx Zone: The Miracle of the New High-Dose Fish Oil. Regan Books. ISBN 0060393130. Discusses "high-dose fish oil;" a newly introduced invented pharmaceutical grade fish oil that Sears touts as a medical miracle that will put the eicasonids in balance and reduce inflammation. Extra virgin olive oil is also promoted for its phytochemicals.
- Sears, Barry (2005). The Anti-Inflammation Zone: Reversing the Silent Epidemic That's Destroying Our Health. Regan Books. ISBN 0060834145.