The Zone diet is a high-fat, low carbohydrate fad diet devised by biochemist Barry Sears. It specifies the consumption of calories from carbohydrates and protein in a specified ratio, recommending eating five times a day to create a sense of satiety that discourages overeating. Like other low-carbohydrate diets, the theories behind this diet are unproven and there is insufficient scientific evidence to determine if it is safe or effective.
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Approach
One of the ideas on which the diet is based is that meals constructed to create a sense of satiety will discourage overeating. Also, like other low-carb diets, the glycemic index is used to classify carbohydrates. Both ideas are meant to promote weight loss via reduction in calories consumed, and avoid spikes in insulin release, thus supporting the maintenance of insulin sensitivity.
The Zone diet proposes that relatively narrow bell-shaped curve centered at 0.75 ratio between proteins and carbohydrates is essential to "balance the insulin to glucagon ratio, which purportedly affects eicosanoid metabolism and ultimately produces a cascade of biological events leading to a reduction in chronic disease risk, enhanced immunity, maximal physical and mental performance, increased longevity and permanent weight loss."
The Zone Diet is a fad diet in the low-carbohydrate diet school that was created by Barry Sears, a biochemist.
The diet advocates eating five times a day, with 3 meals and 2 snacks, and includes eating proteins, carbohydrates - those with a lower glycemic index are considered more favorable, and fats (monounsaturated fats are considered healthier) in a ratio of 30%-40%-30%. The hand is used as the mnemonic tool; five fingers for five times a day, with no more than five hours between meals. The size and thickness of the palm are used to measure protein while two big fists measures favorable carbohydrates and one fist unfavorable carbohydrates. There is a more complex scheme of "Zone blocks" and "mini blocks" that followers of the diet can use to determine the ratios of macronutrients consumed. Daily exercise is encouraged.
The diet falls about midway in the continuum between the USDA-recommended food pyramid which advocates eating grains, vegetables, and fruit and reducing fat, and the high-fat Atkins Diet.
Effectiveness
Like other low-carb diets, the theories underlying the Zone diet are unproven.
As of 2013, there were "no cross sectional or longitudinal studies examining the potential health merit of adopting a Zone Diet per se, [and] closely related peer-reviewed findings from scientific research cast strong doubt over the purported benefits of this diet. When properly evaluated, the theories and arguments of popular low carbohydrate diet books like the Zone rely on poorly controlled, non-peer-reviewed studies, anecdotes and non-science rhetoric."