A randomized clinical trial of a standard versus vegetarian diet for weight loss: the impact of treatment preference.
BACKGROUND
With obesity rampant, methods to achieve sustained weight loss remain elusive.


OBJECTIVE
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.


METHODS
A randomized clinical trial was conducted with 176 adults who were sedentary and overweight (mean body mass index, 34.0 kg/m(2)). 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.


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


RESULTS
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.


CONCLUSIONS
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.
Burke
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Department of Health and Community Systems and the Graduate School of Public Health, Department of Epidemiology, University of Pittsburgh School of Nursing, Pittsburgh, PA, USA. lbu100@pitt.edu
Warziski
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Styn
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Music
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Hudson
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Sereika
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D000005:Abdomen / Q000033:anatomy & histology; D000293:Adolescent; D000328:Adult; D015992:Body Mass Index; D001835:Body Weight / Q000502:physiology; D002784:Cholesterol / Q000097:blood; D018752:Diet, Fat-Restricted; D004038:Diet, Reducing; D014676:Diet, Vegetarian; D006801:Humans; D008875:Middle Aged; D050177:Overweight / Q000097:blood / Q000178:diet therapy*; D014280:Triglycerides / Q000097:blood; D015431:Weight Loss / Q000502:physiology*
D014280:Triglycerides; D002784:Cholesterol