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  • Original Article
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A randomized clinical trial of a standard versus vegetarian diet for weight loss: the impact of treatment preference



With obesity rampant, methods to achieve sustained weight loss remain elusive.


To compare the long-term weight-loss efficacy of 2 cal and fat-restricted diets, standard (omnivorous) versus lacto–ovo–vegetarian, and to determine the effect of a chosen diet versus an assigned diet.

Design, subjects:

A randomized clinical trial was conducted with 176 adults who were sedentary and overweight (mean body mass index, 34.0 kg/m2). Participants were first randomly assigned to either receive their preferred diet or be assigned to a diet group and second, were given their diet of preference or randomly assigned to a standard weight-loss diet or a lacto–ovo–vegetarian diet. Participants underwent a university-based weight-control program consisting of daily dietary and exercise goals plus 12 months of behavioral counseling followed by a 6-month maintenance phase.


Percentage change in body weight, body mass index, waist circumference, low- and high-density lipoprotein, glucose, insulin and macronutrient intake.


The program was completed by 132 (75%) of the participants. At 18 months, mean percentage weight loss was greater (P=0.01) in the two groups that were assigned a diet (standard, 8.0% (s.d., 7.8%); vegetarian, 7.9% (s.d., 8.1%)) than in those provided the diet of their choice (standard, 3.9% (s.d., 6.1%); vegetarian, 5.3% (s.d., 6.2%)). No difference was observed in weight loss between the two types of diet. Over the 18-month program, all groups showed significant weight loss.


Participants assigned to their dietary preference did not have enhanced treatment outcomes. However, all groups lost weight with losses ranging from 4 to 8% at 18 months.

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  1. Ogden C, Carroll M, Curtin L, McDowell M, Tabak C, Flegal K . Prevalence of overweight and obesity in the United States, 1999–2004. JAMA 2006; 295/13: 1549–1555.

    Article  Google Scholar 

  2. Wing RR . Behavioral interventions for obesity: Recognizing our progress and future challenges. Obes Res 2003; 11 (Supp): 3S–5S.

    Article  PubMed  Google Scholar 

  3. Wadden TA, Butryn ML, Byrne KJ . Efficacy of lifestyle modification for long-term weight control. Obes Res 2004; 12 (Suppl): 151S–162S.

    Article  PubMed  Google Scholar 

  4. Wing RR . Behavioral approaches to the treatment of obesity. In: Bray GA, Bourchard C, James WPT (eds). Handbook of Obesity: Clinical Applications. Marcel Dekker: NY, USA, 2004; 147–167.

    Google Scholar 

  5. Janelle KC, Barr SI . Nutrient intakes and eating behavior scores of vegetarian and nonvegetarian women. J Am Diet Assoc 1995; 95/2: 180–189.

    Article  Google Scholar 

  6. White RF, Seymour J, Frank E . Vegetarianism among US women physicians. J Am Diet Assoc 1999; 99/5: 595–598.

    Article  Google Scholar 

  7. Smith C, Burke LE, Wing R . Vegetarian and weight loss diets among young adults. Obes Res 2000; 8/2: 123–129.

    Article  Google Scholar 

  8. Ornish D . Avoiding revascularization with lifestyle changes: The Multicenter Lifestyle Demonstration Project. Am J Cardio 1998; 82: 72T–76T.

    Article  CAS  Google Scholar 

  9. Ornish D, Scherwitz LW, Billings JH, Gould L, Merritt TA, Sparler S et al. Intensive lifestyle changes for reversal of coronary heart disease. JAMA 1998; 280: 2001–2007.

    Article  CAS  PubMed  Google Scholar 

  10. Newby PK, Tucker KL, Wolk A . Risk of overweight and obesity among semivegitarian, lactovegitarian, and vegan women. Am J Clin Nutr 2005; 81: 1267–1274.

    Article  CAS  PubMed  Google Scholar 

  11. Burke LE, Smith CF, Wing RR . Efficacy of a vegetarian diet for weight loss. Obes Res 1999; 7 (Suppl 1): 18S.

    Google Scholar 

  12. Phillips F, Hackett A, Stratton G, Billington D . Effect of changing to a self-selected vegetarian diet on antropometric measurements in UK adults. J Hum Nutr Diet 2004; 17: 249–255.

    Article  CAS  PubMed  Google Scholar 

  13. Rosell M, Appleby P, Spencer E, Key T . Weight gain over 5 years in 21 966 meat-eating, fish-eating, vegetarian, and vegan men and woman in EPIC-Oxford. Int J Obes Relat Metab Disord 2006; 1–8.

  14. Barnard ND, Scialli AR, Turner-McGrievy G, Lanou AJ . Acceptability of a low-fat vegan diet compares favorably to a step II Diet in a randomized controlled trial. J Cardiopulm Rehabil 2004; 24: 229–235.

    Article  PubMed  Google Scholar 

  15. Barnard N, Scialli A, Turner-McGrievy G, Lanou A, Glass J . The effect of low-fat, plant-based dietary intervention on body weight, metabolism, and insulin sensitivity. Am J Med 2005; 118: 991–997.

    Article  CAS  PubMed  Google Scholar 

  16. Murray DC . Preferred versus nonpreferred treatment, and self-control training versus determination raising as treatments of obesity: a pilot study. Psychol Rep 1976; 38: 191–198.

    Article  CAS  PubMed  Google Scholar 

  17. Mendonca PJ, Brehm SS . Effects of choice on behavioral treatment of overweight children. J Soc Clin Psychol 1983; 1/4: 343–358.

    Article  Google Scholar 

  18. Renjilian DA, Perri MG, Nezu AM, McKelvey WF, Shermer RL, Anton SD . Individual versus group therapy for obesity: Effects of matching participants to their treatment preferences. J Consult Clin Psychol 2001; 69/4: 717–721.

    Article  Google Scholar 

  19. King M, Nazareth I, Lampe F, Bower P, Chandler M, Morou M et al. Impact of participant and physician intervention preferences on randomized trials: a systematic review. JAMA 2005; 293/9: 1089–1099.

    Article  Google Scholar 

  20. Epstein LH . Role of behavior theory in behavioral medicine. J Consult Clin Psychol 1992; 60/4: 493–498.

    Article  Google Scholar 

  21. Burke LE, Choo J, Music E, Warziski M, Styn MA, Kim Y et al. PREFER study: a randomized clinical trial testing treatment preference and two dietary options in behavioral weight management—rationale, design and baseline characteristics. Contemp Clin Trials 2006; 27/1: 34–48.

    Article  Google Scholar 

  22. Pocock SJ, Simon RM . Sequential treatment assignment with balancing for prognostic factors in the controlled clinical trials. Biometrics 1975; 31: 103–115.

    Article  CAS  PubMed  Google Scholar 

  23. Wing RR . Behavioral approaches to the treatment of obesity. In: Bray GA, Bourchard C, James WPT (eds). Handbook of Obesity. Marcel Dekker: NY, USA, 1998 pp 855–877.

    Google Scholar 

  24. Friedewald WT, Levy RI, Fredickson DA . Estimation of the concentration of low-density cholesterol in plasma without the use of the preparative ultracentrifuge. Clin Chem 1972; 18: 499–502.

    CAS  PubMed  Google Scholar 

  25. Jakicic J, Winters C, Lang W, Wing R . Effects of intermittent exercise and use of home exercise equipment on adherence, weight loss, and fitness in overweight women: a randomized trial. JAMA 1999; 282/16: 1554–1560.

    Article  Google Scholar 

  26. Daby R . Expressed preference for, and assignment to one of two weight loss programs: effects on weight loss and weight loss maintenance. Psychology 1988. Tennessee, Vanderbilt 113.

  27. Fuller TC . The role of patient preferences for treatment type in the modification of weight loss behavior. Unpublished Dissertation 1988; Michigan State University.

  28. Osterberg L, Blaschke TF . Adherence to medication. N Engl J Med 2005; 353/5: 487–497.

    Article  Google Scholar 

  29. Golin CE, DiMatteo MR, Gelberg L . The role of patient participation in the doctor visit: implications for adherence to diabetes care. Diabetes Care 1996; 19/10: 1153–1164.

    Article  Google Scholar 

  30. Feldman R, Bacher M, Campbell N, Drover A, Chockalingam A . Adherence to pharmacologic management of hypertension. Can J Public Health 1998; 89/5: I16–I18.

    Google Scholar 

  31. Smith CF, Burke LE, Wing RR . Young adults remain on vegetarian diets longer than on weight loss diets. Ann Behav Med 1999; 21 (Supp): 90.

    Google Scholar 

  32. Tate DF, Jackvony EH, Wing RR . Effects of internet behavioral counseling on weight loss in adults at risk for type 2 diabetes: a randomized trial. JAMA 2003; 289/14: 1833–1836.

    Article  Google Scholar 

  33. Bish CL, Blanck HM, Serdula MK, Marcus M, Kohl III HW, Khan LK . Diet and physical activity behaviors among Americans trying to lose weight: 2000 Behavioral risk factor surveillance system. Obes Res 2005; 13/3: 596–607.

    Article  Google Scholar 

  34. Weiss EC, Galuska DA, Khan LK, Serdula MK . Weight-control practices among US adults, 2001–2002. Am J Prev Med 2006; 31/1: 18–24.

    Article  Google Scholar 

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This study was supported by National Institutes of Health grants NIH, NIDDK, no. RO1-DK58631. The conduct of the study was also supported by the Data Management Core of the Center for Research in Chronic Disorders NIH-NINR no. P30-NR03924, the Obesity and Nutrition Research Center NIH-NIDDK no. DK-046204, the Heinz Nutrition Laboratory and the General Clinical Research Center, NIH-NCRR-GCRC no. 5MO1-RR00056 at the University of Pittsburgh. We thank the study participants who graciously shared their time and information with us.

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Correspondence to L E Burke.

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Burke, L., Warziski, M., Styn, M. et al. A randomized clinical trial of a standard versus vegetarian diet for weight loss: the impact of treatment preference. Int J Obes 32, 166–176 (2008).

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