Changes in self-efficacy and dietary adherence: the impact on weight loss in the PREFER study.

Findings from studies examining self-efficacy and its relationship to weight loss have been inconsistent. We examined self-efficacy specific to changing eating behaviors in the PREFER trial, an 18-month behavioral weight-loss study, to determine if self-efficacy and dietary adherence were associated with weight change, and what impact self-efficacy had on weight change after controlling for adherence. Measurements included the weight efficacy lifestyle (WEL) questionnaire, body weight, self-reported fat gram intake, kilocalorie intake, and adherence to kilocalorie and fat gram goals at baseline, 6, 12, and 18 months. The sample (N = 170) was 88.2% female and 70.0% Caucasian; the mean age was 44.1 years (SD = 8.8). Mean weight loss at 18 months was 4.64% (SD = 6.24) of baseline body weight and the mean increase in self-efficacy was 11.70% (SD = 38.61). Self-efficacy improved significantly over time (p = 0.04) and was associated with weight loss (p = 0.02). Adherence to the fat gram goal was associated with weight loss (p = 0.0003), and self-efficacy remained associated with weight loss after controlling for fat gram adherence (p = 0.0001). Consistent with self-efficacy theory, improvement in self-efficacy over time supported greater weight loss. Adherence to the fat gram goal also influenced weight loss.

Effects of a vegetarian diet and treatment preference on biochemical and dietary variables in overweight and obese adults: a randomized clinical trial.

BACKGROUND: A vegetarian diet may lead to numerous health benefits, including weight loss. OBJECTIVE: 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. DESIGN: 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. RESULTS: 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. CONCLUSIONS: 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 www.clinicaltrials.gov as NCT00330629.