The Zone diet is a diet popularized in books by biochemist Barry Sears. It advocates consuming calories from carbohydrates and protein in a balanced ratio. There is no evidence that it makes people more healthy.
The diet teaches followers to eat five times a day, 3 meals and 2 snacks, with proteins, favorable carbohydrates, and fats in a ratio of 30-40-30. The hand is used as mnemonic tool; five fingers for five times a day, and no more than five hours between meals; the size and thickness of the palm to measure protein; and two big fists worth of favorable carbohydrates or one fist of unfavorable carbohydrates. There is a more complex scheme of "Zone blocks" and "miniblocks" that followers of the diet can use to determine ratios of macronutrients to eat. Favorable carbohydrates have a lower glycemic index. Monounsaturated fats are encouraged. Followers are encourage to exercise daily.
Like other low-carb diets, one of the ideas on which the diet is based, is constructing meals carefully to cause a sense of satiety so that followers of the diet do not overeat. Also like other low-carb diets, the idea of a 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 retention of insulin sensitivity.
The Zone diet proposes that the precise ratio betweens proteins and carbohydrates is essential to "reduce 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.
As of 2013, there were "no cross sectional or longitudinal studies examining the potential health merit of adopting a Zone Diet per se, 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."
- DeBruyne L, Pinna K, Whitney E (2011). "Chapter 7: Nutrition in practice — Fad Diets". [http://books.google.com/books?id=GaEKAAAAQBAJ&pg=PT20 9 Nutrition and Diet Therapy]. Nutrition and Diet Therapy (Cengage Learning). p. 209. ISBN 1-133-71550-8.
"a fad diet by any other name would still be a fad diet." And the names are legion: the Atkins Diet, the Cheater's Diet, the South Beach Diet, the Zone Diet. Year after year, "new and improved" diets appear ...
- Baron M. Fighting obesity Part 1: Review of popular low-carb diets. Health Care Food Nutr Focus. 2004 Oct;21(10):1, 3-6, 11. Review. PMID 15493377
- Baron M. The Zone Diet. Health Care Food Nutr Focus. 2004 Oct;21(10):8-9, 11. PMID 15493380
- Lara-Castro C, Garvey WT. Diet, insulin resistance, and obesity: zoning in on data for Atkins dieters living in South Beach. J Clin Endocrinol Metab. 2004 Sep;89(9):4197-205. PMID 15356006
- Cheuvront SN The Zone Diet phenomenon: a closer look at the science behind the claims. J Am Coll Nutr. 2003 Feb;22(1):9-17. PMID 12569110