Background: Choosing a diet rather than being prescribed one could improve weight loss.
Objective: To examine whether offering choice of diet improves weight loss.
Design: Double-randomized preference trial of choice between 2 diets (choice) versus random assignment to a diet (comparator) over 48 weeks. (ClinicalTrials.gov: NCT01152359).
Setting: Outpatient clinic at a Veterans Affairs medical center.
Patients: Outpatients with a body mass index of at least 30 kg/m2.
Intervention: Choice participants received information about their food preferences and 2 diet options (low-carbohydrate diet [LCD] or low-fat diet [LFD]) before choosing and were allowed to switch diets at 12 weeks. Comparator participants were randomly assigned to 1 diet for 48 weeks. Both groups received group and telephone counseling for 48 weeks.
Measurements: The primary outcome was weight at 48 weeks.
Results: Of 105 choice participants, 61 (58%) chose the LCD and 44 (42%) chose the LFD; 5 (3 on the LCD and 2 on the LFD) switched diets at 12 weeks, and 87 (83%) completed measurements at 48 weeks. Of 102 comparator participants, 53 (52%) were randomly assigned to the LCD and 49 (48%) were assigned to the LFD; 88 (86%) completed measurements. At 48 weeks, estimated mean weight loss was 5.7 kg (95% CI, 4.3 to 7.0 kg) in the choice group and 6.7 kg (CI, 5.4 to 8.0 kg) in the comparator group (mean difference, -1.1 kg [CI, -2.9 to 0.8 kg]; P = 0.26). Secondary outcomes of dietary adherence, physical activity, and weight-related quality of life were similar between groups at 48 weeks.
Limitations: Only 2 diet options were provided. Results from this sample of older veterans might not be generalizable to other populations.
Conclusion: Contrary to expectations, the opportunity to choose a diet did not improve weight loss.