Zone diet
Trials that tested Zone by name found weight loss similar to or below other popular diets, 1.6 to 3.2 kg at a year. In insulin-resistant women it lowered weight and triglycerides more than a high-carbohydrate diet. A 1-week study in 8 athletes found shorter time to exhaustion. Micronutrient adequacy improved in one trial, and dropout was high.
- Status
- A named diet program, not a regulated product.
- Also called
- The Zone, Zone, 40-30-30 diet
- Followed for
- weight loss, heart health, blood sugar, inflammation, athletic performance
Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on
Shown to help2
What people follow it for, and what was found
Shown to help2
Weight loss
Shown to produce weight loss similar to Atkins, Weight Watchers and Ornish in one trial, and less than Atkins in another 1-year trial.
Compared with the Atkins, LEARN and Ornish diets [1]; the Atkins, Weight Watchers and Ornish diets [2]; the Atkins diet and other named diet programs, in a network meta-analysis against no diet [3]; a conventional high-carbohydrate, high-fibre diet and the high-fat Atkins diet [4]; a low-carbohydrate high-protein ketogenic diet and a conventional hypocaloric diabetic exchange diet [5]
The numbers and sources
- Effect
- At 12 months, women lost 1.6 kg on Zone (95% CI 0.4 to 2.8) against 4.7 kg on Atkins, a significant difference, and 2.6 kg on LEARN and 2.2 kg on Ornish [1]. In another 1-year trial, mean loss was 3.2 kg on Zone, 2.1 kg on Atkins, 3.0 kg on Weight Watchers and 3.3 kg on Ornish, and loss tracked adherence, not diet type [2]. In a network meta-analysis, Atkins produced 1.71 kg more loss than Zone at 6 months, and differences between named diets were minimal [3]. In insulin-resistant women, Zone produced 2.7 kg more loss than a high-carbohydrate diet [4]. In a 12-week trial, weight, fat and lean mass loss did not differ between Zone, a ketogenic diet and a conventional diet [5].
- Population
- 311 premenopausal women with overweight or obesity [1]; 160 adults with cardiac risk factors [2]; 7,286 adults in 48 trials [3]; 96 insulin-resistant women [4]; adults in a 3-arm trial with DXA body composition [5].
- Sources
- [1], [2], [3], [4], [5]
- Caveats
- Adherence was low in one trial and attrition high in another [2][5]. Most trials ran 12 months or less.
Inflammation markers
One small trial found Zone added to the drop in the blood arachidonic acid to EPA ratio produced by omega-3 supplements.
Compared with the diet suggested by the Italian National Research Institute for Nutrition and Foods, each with omega-3 or placebo [6]
The numbers and sources
- Effect
- Omega-3 supplements strongly lowered the arachidonic acid to EPA ratio, with an additional effect of diet, particularly Zone. Zone also lowered skinfold thickness and body fat percentage against an Italian national institute diet [6].
- Population
- 33 people without known disease over 70 days [6].
- Sources
- [6]
- Caveats
- One small trial in which diet was open-label. The ratio is a blood marker, and the abstract does not give its size [6].
Mixed results1
Heart and metabolic markers
Small trials found Zone lowered triglycerides more than a high-carbohydrate diet in one, and heart risk factors changed similarly across four diets in another.
Compared with the Atkins, Ornish and Weight Watchers diets [2]; a conventional high-carbohydrate, high-fibre diet and the high-fat Atkins diet [4]
The numbers and sources
- Effect
- Against a high-carbohydrate diet, triglycerides fell 0.22 mmol/L more and waist 2.7 cm more. LDL fell, and ended 0.28 mmol/L lower than on Atkins (95% CI 0.04 to 0.52). LDL rose more than 10% in 3% on Zone, 13% on the high-carbohydrate diet and 25% on Atkins. Insulin fell on all three diets [4]. In another trial, each of four diets lowered the LDL to HDL ratio by about 10%, with no significant change in blood pressure or glucose at 1 year [2].
- Population
- 96 insulin-resistant women without diabetes [4]; 160 adults with cardiac risk factors [2].
- Sources
- [2], [4]
- Caveats
- Small trials of blood markers, not heart attacks or strokes.
Not shown to help1
Athletic performance
One small study found time to exhaustion fell from 37.7 to 34.1 minutes after a week on Zone in 8 male endurance athletes.
Compared with before the diet, in the same runners, on their normal diet [7]
The numbers and sources
- Effect
- After 7 days, energy intake fell from 2,314 to 1,994 kcal, body mass from 70.7 to 69.8 kg, and running time to exhaustion at 80% of VO2 max from 37.68 to 34.11 minutes [7].
- Population
- 8 recreational male endurance athletes, mean age 26 [7].
- Sources
- [7]
- Caveats
- Very small and only 1 week. Before-and-after design against each runner's normal diet [7].
How trials defined it
One trial defined Zone as about 40% of calories from carbohydrate, against under 10% on a ketogenic diet and 50% on a conventional diet [5]. Another described it as macronutrient balance, with 2 months of maximum effort before people chose their own adherence [2]. In insulin-resistant women, Zone was the high-protein arm, taught as food choice advice without an energy target [4]. Trials ran from 7 days [7] to 12 months [1][2].
Risks
Reported risks1
Dropout
Limited evidence: 60% dropped out of Zone in one 12-week trial and 35% in a 1-year trial, similar to or more than other diets.
The numbers and sources
- Effect
- Attrition was 60% on Zone, 43% on a ketogenic diet and 36% on a conventional diet over 12 weeks [5]. Over 1 year, 26 of 40 completed Zone, the same as Weight Watchers, against 21 on Atkins and 20 on Ornish [2].
- Population
- Adults in a 3-arm trial [5]; 160 adults with cardiac risk factors [2].
- Sources
- [2], [5]
- Caveats
- Two small trials.
Checked, no increase found1
Micronutrient intake
One trial found no rise in risk of inadequate micronutrient intake on Zone after 8 weeks, and lower risk for vitamins A, C, E and K.
The numbers and sources
- Effect
- After 8 weeks, risk of inadequacy fell for vitamins A, E, K and C on Zone, with no significant increase for other micronutrients. On Atkins, Ornish and LEARN, some micronutrients moved toward inadequacy [8].
- Population
- 73 women with overweight or obesity on Zone, among 291 in four diet arms [8].
- Sources
- [8]
- Caveats
- Intake from 24-hour recalls, not blood levels [8].
Claims tested and not found
- That Zone improves endurance performance. Time to exhaustion fell after a week on the diet, and the authors found the claim of better performance not shown [7].
- That Zone produces more weight loss than other popular diets. At 12 months, loss on Zone was the smallest of four diets in one trial [1], and differences between named diets were minimal in a network meta-analysis [3].
Sources
- Gardner CD, Kiazand A, Alhassan S, et al. Comparison of the Atkins, Zone, Ornish, and LEARN diets for change in weight and related risk factors among overweight premenopausal women: the A TO Z Weight Loss Study: a randomized trial. JAMA. 2007. https://doi.org/10.1001/jama.297.9.969
- Dansinger ML, Gleason JA, Griffith JL, et al. Comparison of the Atkins, Ornish, Weight Watchers, and Zone diets for weight loss and heart disease risk reduction: a randomized trial. JAMA. 2005. https://doi.org/10.1001/jama.293.1.43
- Johnston BC, Kanters S, Bandayrel K, et al. Comparison of weight loss among named diet programs in overweight and obese adults: a meta-analysis. JAMA. 2014. https://doi.org/10.1001/jama.2014.10397
- McAuley KA, Hopkins CM, Smith KJ, et al. Comparison of high-fat and high-protein diets with a high-carbohydrate diet in insulin-resistant obese women. Diabetologia. 2005. https://doi.org/10.1007/s00125-004-1603-4
- Landers P, Wolfe MM, Glore S, et al. Effect of weight loss plans on body composition and diet duration. The Journal of the Oklahoma State Medical Association. 2002. https://pubmed.ncbi.nlm.nih.gov/12043107/
- Fontani G, Corradeschi F, Felici A, et al. Blood profiles, body fat and mood state in healthy subjects on different diets supplemented with Omega-3 polyunsaturated fatty acids. European Journal of Clinical Investigation. 2005. https://doi.org/10.1111/j.1365-2362.2005.01540.x
- Jarvis M, McNaughton L, Seddon A, et al. The acute 1-week effects of the Zone diet on body composition, blood lipid levels, and performance in recreational endurance athletes. Journal of Strength and Conditioning Research. 2002. https://doi.org/10.1519/1533-4287(2002)016<0050:taweot>2.0.co;2
- Gardner CD, Kim S, Bersamin A, et al. Micronutrient quality of weight-loss diets that focus on macronutrients: results from the A TO Z study. The American Journal of Clinical Nutrition. 2010. https://doi.org/10.3945/ajcn.2010.29468