Zone diet
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The Zone diet is a fad diet emphasizing low-carbohydrate consumption.<ref name=Cheuvront /><ref name=fad>Template:Cite book</ref> It was created by Barry Sears, an American biochemist.<ref name=Bijlefeld>Template:Cite book</ref><ref name=Baron1>Template:Cite journal</ref><ref name=Baron2>Template:Cite journal</ref>
The ideas behind the diet are not supported by scientific evidence.<ref name=Cheuvront /><ref name="Cataldo">Cataldo, Corrine Balog; DeBruyne, Linda Kelly; Whitney, Eleanor Noss. (1999). Nutrition and Diet Therapy: Principles and Practice. West/Wadsworth. p. 214. Template:ISBN "Most fad diets, including the currently popular Zone Diet, advocate essentially the same high-protein, low- carbohydrate diet. Such diets may offer short-term weight- loss success to some who try them, but they fail to produce long-lasting results for most people. Furthermore, high protein, low-carbohydrate diets are often high in fat and low in fiber, vitamins, and some minerals. Long-term use of such diets may produce adverse side effects such as nausea, fatigue, constipation, and low blood pressure."</ref>
Approach
The diet is meant to promote weight loss via reduction in calories consumed and avoid spikes in insulin release, thus supporting the maintenance of insulin sensitivity.<ref name=Baron1 /><ref name=Lara /> It begins with the determination of the individual's protein requirement for daily replacement due to various loss mechanisms. The diet then adjusts carbohydrate and fat intake based on the person’s energy needs and weight loss goalsThe Zone diet proposes that a relatively narrow distribution in the ratio of proteins to carbohydrates, centered at 0.75, 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."<ref name="Cheuvront">Template:Cite journal</ref>
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 caloric ratio of 30%-40%-30% (fat-carb-pro). 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 measure 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.<ref name=Baron2 />
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.<ref name=Lara>Template:Cite journal</ref>
Effectiveness
Like other low-carb diets, the ideas underlying the Zone diet are unproven.<ref name=Cheuvront /><ref name=Baron1 /><ref name="Cataldo" />
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 ideas and arguments of popular low carbohydrate diet books like the Zone rely on poorly controlled, non-peer-reviewed studies, anecdotes and non-science rhetoric."<ref name=Cheuvront />