A Randomized Clinical Trial Testing Treatment Preference and Two Dietary Options in Behavioral Weight Management: Preliminary Results of the Impact of Diet at 6 Months—PREFER Study*

School of Nursing, University of Pittsburgh, 3500 Victoria Street, 415 Victoria Building, Pittsburgh, PA 15261, USA.
Obesity (Impact Factor: 3.73). 11/2006; 14(11):2007-17. DOI: 10.1038/oby.2006.235
Source: PubMed


The PREFER study objectives were to examine potential differences in weight loss during a standard behavioral intervention between subjects assigned to one of two calorie- and fat-restricted diets [standard behavior treatment (SBT) and lacto-ovo-vegetarian ([SBT+LOV)], with or without regard to their preferred dietary treatment. This article reports the differences in outcomes between diet groups after the first 6 months of the intervention.
The study used a four-group design. Subjects (n = 182) were randomized to a treatment preference group and then to a dietary treatment group. For this report, preference groups were combined to permit comparisons by dietary treatment only (SBT, n = 98; SBT+LOV, n = 84). Additional analyses compared SBT+LOV subjects who were 100% adherent (did not consume any meat, fish, or poultry, n = 47) to those who were <100% adherent (n = 24).
Significant differences were seen in the baseline to 6-month change scores between the two groups for carbohydrate consumption (p = 0.013), protein consumption (p < 0.001), polyunsaturated-to-saturated fat ratio (p = 0.009), and low-density lipoprotein-cholesterol (LDL-C) level (p = 0.013). Among SBT+LOV subjects, those who were 100% adherent experienced greater reductions in weight (p < 0.001), total cholesterol (p = 0.026), LDL-C (p = 0.034), and glucose (p = 0.002) and consumed less fat (p = 0.030) compared with those who were <100% adherent.
Differences between dietary treatment groups at 6 months were minimal, most likely because one-third of the SBT+LOV group did not follow the vegetarian diet and because both groups had the same calorie and fat restrictions. SBT+LOV subjects who were 100% adherent were more successful at both weight loss and cholesterol reduction than those who were <100% adherent, suggesting that vegetarian diets are efficacious for weight and cholesterol control.

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    ABSTRACT: A vegetarian diet may lead to numerous health benefits, including weight loss. We examined the joint effects of personal preference of dietary treatment and a calorie-restricted, low-fat lactoovovegetarian diet (LOV-D) compared with a standard calorie-restricted, low-fat omnivorous diet (STD-D) on changes in weight, total cholesterol, ratio of LDL to HDL cholesterol (LDL:HDL cholesterol), triacylglycerols, insulin resistance, and macronutrient intake during an 18-mo study. This was a randomized clinical trial of 176 overweight and obese adults who were recruited and randomly assigned first to 1 of 2 preference conditions (yes or no). If assigned to Preference-No, they were randomly assigned to 1 of the 2 diet conditions (STD-D or LOV-D). If assigned to Preference-Yes, they were assigned to the diet they indicated as preferred at screening. The 12-mo intervention was followed by a 6-mo maintenance phase. Participants were mainly women (86.9%) and white (70.5%); 75% completed the 18-mo study. A significant interaction between preference and dietary treatment was not observed for any of the outcome variables. However, participants in the Preference-No groups significantly decreased their triacylglycerols (P = 0.04). The only effect observed for diet was a borderline significant decrease in LDL:HDL cholesterol for the LOV-D group (P = 0.06). Within the LOV-D groups, those who were 100% adherent to the LOV-D had significant and marginally significant reductions in monounsaturated fat (P = 0.02) and total fat (P = 0.05) intakes at 18 mo. Our findings suggest that neither prescribing a vegetarian diet nor allowing persons to choose their preferred diet had a significant effect on outcome measures. However, all participants had a significant reduction in total energy and fat intakes and an increase in energy expenditure, which was reflected in reduced body weight. This clinical trial was registered at as NCT00330629.
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    ABSTRACT: Overweight and obesity are widespread, global health problems due in part to the relapse and weight gain that often follows weight loss treatment. Moreover, racial minorities are disproportionately affected by this chronic disorder. Empirical evidence is needed to better address the problem of poor weight maintenance after loss. This ancillary, prospective study examined weight maintenance 18 months after a behavioral weight loss trial and explored possible differences between black and white participants in percent weight change and successful weight maintenance. The relationships of psychosocial variables - experiences following a low-fat diet, barriers to healthy eating, self-efficacy for resisting eating and for exercising, social support, and stress - with weight maintenance were investigated as well as whether race moderated these relationships. Additionally, the study examined the behavioral strategies used for weight maintenance and explored dietary intake and physical activity as potential mediators of the relationship between psychosocial variables and weight maintenance. Hierarchical linear and logistic regression models were used to examine the effect of race, as well as the effect of psychosocial variables, on percent weight change and successful weight maintenance (defined as ≤ 5% weight regain), after controlling for age, gender, education, income, and marital status. Descriptive statistics and group comparative statistics (t-tests or Mann Whitney U tests) were used to examine behavioral strategies utilized for weight maintenance. Path analysis investigated possible mediation effects of lifestyle variables on percent weight change. Fifty-seven percent of the 107 participants (58% of the 81 white participants and 54% of the 26 black participants) were successful weight maintainers. No difference was found in weight maintenance between racial groups; black and white individuals gained a similar amount of weight (M = 5.0%, SD = 6.6% and M = 4.4%, SD = 5.6%, respectively). An increase in barriers to healthy eating and the impact of a stressful life event on eating affected the percent weight gained and unsuccessful weight maintenance, ps < .04. Most behavioral strategies for weight maintenance were used less than half the time. Dietary intake and physical activity did not mediate the relationship between the examined psychosocial variables and weight maintenance.A difference in weight maintenance between black and white individuals was not supported by this study. Future research should further explore the weight control barriers that individuals experience and the impact of stress on weight maintenance.
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