Zone Diet Validation Studies

Review published literature to see how the Zone Diet and findings from Dr. Barry Sears stack up in various areas of nutritional research, including weight loss, reduction of cellular inflammation, heart disease, diabetes, and ease of use. 

Weight Loss

Any diet that restricts calories will result in equivalent weight loss. However, the same doesn’t hold true as to what the source of that weight loss is. Weight loss from either dehydration (such as ketogenic diets) or cannibalization of muscle and organ mass (such as low-protein diets) has no health benefits. Only when the weight loss source is from stored fat do you gain any health benefits. Here the Zone diet has been shown to be superior to all other diets in burning fat faster (1-4). It has been demonstrated that if a person has a high initial insulin response to a glucose challenge, then the Zone diet is also superior in weight loss (5,6). A recent study from the New England Journal of Medicine indicates that a diet composition similar to the Zone diet is superior to other compositions in preventing the regain of lost weight (7). This is probably caused by the increased satiety induced by the Zone diet compared to other diets (1,8,9).

Reduction of cellular inflammation

There is total agreement in the research literature that the Zone diet is superior in reducing cellular inflammation (10-12). Since cellular inflammation is the driving force for chronic disease, then this should be the ultimate goal of any diet. Call me crazy for thinking otherwise.

Heart disease

It is ironic that the Ornish diet is still considered one of the best diets for heart disease, since the published data indicates that twice as many people had fatal heart attacks on the Ornish diet compared to a control diet (13). This is definitely the case of don’t confuse me with the facts. On the other hand, diets with the same balance of protein, carbohydrate and fat as the Zone diet has have been shown to be superior in reducing cardiovascular risk factors, such as cholesterol and fasting insulin (14,15).

Diabetes

The first publication validating the benefits of the Zone diet in treating diabetes appeared in 1998 (16). Since that time there have been several other studies indicating the superiority of the Zone diet composition for reducing blood glucose levels (17-20). In 2005, the Joslin Diabetes Research Center at Harvard Medical School announced its new dietary guidelines for treating obesity and diabetes. These dietary guidelines were essentially identical to the Zone diet. Studies done at the Joslin Diabetes Research Center following those dietary guidelines confirm the efficacy of the Zone diet to reduce diabetic risk factors (21). If the Zone diet isn’t recommended for individuals with diabetes, then someone should tell Harvard.

Ease of use

The Zone diet simply requires balancing one-third of your plate with low-fat protein with the other two-thirds coming from fruits and vegetables (i.e. colorful carbohydrates). Then you add a dash (that’s a small amount) of heart-healthy monounsaturated fats. The Zone diet is based on a bell-shaped curve balancing low-fat protein and low-glycemic-index carbohydrates, not a particular magic number. If you balance the plate as described above using your hand and your eye, it will approximate 40 percent of the calories as carbohydrates, 30 percent of calories as protein, and 30 percent of the calories as fat. Furthermore, it was found in a recent Stanford University study that the Zone diet provided greater amounts of micronutrients on a calorie-restricted program than any other diet (22).

Eventually all dietary theories have to be analyzed in the crucible of experimentation to determine their validity. So far in the past 13 years since I wrote my first book, my concepts of anti-inflammatory nutrition still seem to be at the cutting edge.

References:

1. Skov AR, Toubro S, Ronn B, Holm L, and Astrup A. “Randomized trial on protein vs carbohydrate in ad libitum fat reduced diet for the treatment of obesity.” Int J Obes Relat Metab Disord 23: 528-536 (1999).
2. Layman DK, Boileau RA, Erickson DJ, Painter JE, Shiue H, Sather C, and Christou DD. “A reduced ratio of dietary carbohydrate to protein improves body composition and blood lipid profiles during weight loss in adult women.” J Nutr 133: 411-417 (2003).
3. Fontani G, Corradeschi F, Felici A, Alfatti F, Bugarini R, Fiaschi AI, Cerretani D, Montorfano G, Rizzo AM, and Berra B. “Blood profiles, body fat and mood state in healthy subjects on different diets supplemented with omega-3 polyunsaturated fatty acids.” Eur J Clin Invest 35: 499-507 (2005).
4. Layman DK, Evans EM, Erickson D, Seyler J, Weber J, Bagshaw D, Griel A, Psota T, and Kris-Etherton P. “A moderate-protein diet produces sustained weight loss and long-term changes in body composition and blood lipids in obese adults.” J Nutr 139: 514-521 (2009).
5. Ebbeling CB, Leidig MM, Feldman HA, Lovesky MM, and Ludwig DS. “Effects of a low-glycemic-load vs low-fat diet in obese young adults: a randomized trial.” JAMA 297: 2092-2102 (2007).
6. Pittas AG, Das SK, Hajduk CL, Golden J, Saltzman E, Stark PC, Greenberg AS, and Roberts SB. "A low-glycemic-load diet facilitates greater weight loss in overweight adults with high insulin secretion but not in overweight adults with low insulin secretion in the CALERIE Trial." Diabetes Care 28: 2939-2941 (2005).
7. Larsen TM, Dalskov SM, van Baak M, Jebb SA, Papadaki A, Pfeiffer AF, Martinez JA, Handjieva-Darlenska T, Kunesova M, Pihlsgard M, Stender S, Holst C, Saris WH, and Astrup A. “Diets with high or low protein content and glycemic index for weight-loss maintenance.” N Engl J Med 363: 2102-2113 (2010).
8. Ludwig DS, Majzoub JA, Al-Zahrani A, Dallal GE, Blanco I, Roberts SB, Agus MS, Swain JF, Larson CL, and Eckert EA. “Dietary high-glycemic-index foods, overeating, and obesity.” Pediatrics 103: E26 (1999).
9. Agus MS, Swain JF, Larson CL, Eckert EA, and Ludwig DS. “Dietary composition and physiologic adaptations to energy restriction.” Am J Clin Nutr 71: 901-907 (2000).
10. Pereira MA, Swain J, Goldfine AB, Rifai N, and Ludwig DS. “Effects of a low-glycemic-load diet on resting energy expenditure and heart disease risk factors during weight loss.” JAMA 292: 2482-2490 (2004).
11. Pittas AG, Roberts SB, Das SK, Gilhooly CH, Saltzman E, Golden J, Stark PC, and Greenberg AS. “The effects of the dietary glycemic load on type 2 diabetes risk factors during weight loss.” Obesity 14: 2200-2209 (2006).
12. Johnston CS, Tjonn SL, Swan PD, White A, Hutchins H, and Sears B. “Ketogenic low-carbohydrate diets have no metabolic advantage over nonketogenic low-carbohydrate diets.” Am J Clin Nutr 83: 1055-1061 (2006).
13. Ornish D, Scherwitz LW, Billings JH, Brown SE, Gould KL, Merritt TA, Sparler S, Armstrong WT, Ports TA, Kirkeeide RL, Hogeboom C, and Brand RJ, “Intensive lifestyle changes for reversal of coronary heart disease.” JAMA 280: 2001-2007 (1998).
14. Wolfe BM and Piche LA. “Replacement of carbohydrate by protein in a conventional-fat diet reduces cholesterol and triglyceride concentrations in healthy normolipidemic subjects.” Clin Invest Med 22: 140-1488 (1999).
15. Dumesnil JG, Turgeon J, Tremblay A, Poirier P, Gilbert M, Gagnon L, St-Pierre S, Garneau C, Lemieux I, Pascot A, Bergeron J, and Despres JP. “Effect of a low-glycaemic index, low-fat, high-protein diet on the atherogenic metabolic risk profile of abdominally obese men.” Br J Nutr 86:557-568 (2001).
16. Markovic TP, Campbell LV, Balasubramanian S, Jenkins AB, Fleury AC, Simons LA, and Chisholm DJ. “Beneficial effect on average lipid levels from energy restriction and fat loss in obese individuals with or without type 2 diabetes.” Diabetes Care 21: 695-700 (1998).
17. Layman DK, Shiue H, Sather C, Erickson DJ, and Baum J. “Increased dietary protein modifies glucose and insulin homeostasis in adult women during weight loss.” J Nutr 133: 405-410 (2003).
18. Gannon MC, Nuttall FQ, Saeed A, Jordan K, and Hoover H. “An increase in dietary protein improves the blood glucose response in persons with type 2 diabetes.” Am J Clin Nutr 78: 734-741 (2003).
19. Nuttall FQ, Gannon MC, Saeed A, Jordan K, and Hoover H. “The metabolic response of subjects with type 2 diabetes to a high-protein, weight-maintenance diet.” J Clin Endocrinol Metab 2003 88: 3577-3583 (2003).
20. Gannon MC and Nuttall FQ. “Control of blood glucose in type 2 diabetes without weight loss by modification of diet composition.” Nutr Metab (Lond) 3: 16 (2006).
21. Hamdy O and Carver C. “The Why WAIT program: improving clinical outcomes through weight management in type 2 diabetes.” Curr Diab Rep 8: 413-420 (2008).
22. Gardner CD, Kim S, Bersamin A, Dopler-Nelson M, Otten J, Oelrich B, and Cherin R. “Micronutrient quality of weight-loss diets that focus on macronutrients: results from the A TO Z study.” Am J Clin Nutr 92: 304-312 (2010).