HSR&D Home » Research » IIR 09-381 – HSR&D Study
Considering Patient Diet Preference to Optimize Weight Loss
William S Yancy, MD MHS
Durham VA Medical Center, Durham, NC
Funding Period: October 2010 - September 2013
The prevalence of obesity (body mass index [BMI] 30 kg/m2) in US adults has skyrocketed over the past 30 years, affecting approximately 33% in the VA nationally in 2000 and approximately 36% at the Durham VAMC currently. Thus, identifying effective strategies for treating obesity is both a public health and a VA priority. A variety of diet approaches have proven successful in achieving moderate weight loss in many individuals. Most diet interventions fail to achieve meaningful weight loss in more than a few individuals. This failure likely results from inadequate adherence to the diet.
The proposed study will test the commonly proposed assumption that helping patients to choose a diet based on their dietary preferences will increase weight loss success relative to assigning or recommending a single diet. The objectives of this study are to: (a) examine the difference in weight loss at 48 weeks among participants randomized to the Choice arm versus participants randomized to the Control arm; (b) examine the difference in diet adherence at 48 weeks among participants randomized to the Choice arm versus participants randomized to the Control arm; and (c) examine the difference in obesity-specific health-related quality of life (HRQOL) at 48 weeks among participants randomized to the Choice arm versus participants randomized to the Control arm.
The proposed study is a 2-arm randomized controlled trial involving 216 outpatients from Durham VA Medical Center. Participants must be obese (BMI 30 kg/m) VAMC outpatients without unstable health issues. Participants in the experimental arm (Choice) will select either a low-carbohydrate, calorie-unrestricted diet (LCD) or a low-fat, reduced-calorie diet (LFD) after being informed by results from a validated food preference questionnaire and a discussion of available diet options with trained personnel. The Choice participants will also have the opportunity to switch to the other diet after 3 months if unsuccessful or dissatisfied with their primary selection. Participants in the Control arm will be randomly assigned to follow one of the two diets for the duration of follow-up. All participants will receive diet-appropriate counseling in small group meetings every 2 weeks for 24 weeks, then monthly for another 24 weeks. All participants will also receive brief telephone counseling involving individual goal setting and problem solving halfway through each month in the latter 24 weeks.
The primary outcome is weight change from baseline to 48 weeks. Secondary outcomes include adherence to diet by food frequency questionnaire and obesity-specific health-related quality of life. Exploratory analyses will examine whether the impact of choice versus lack of choice on weight loss is moderated by individual differences in the constructs of autonomy orientation, competence, and relatedness.
A total of 207 participants were enrolled. Mean age was 54 (SD=11) years, 27% were women, 51% were White, 43% were Black, 22% had diabetes. Mean weight at baseline was 109 (SD=21) kg and mean BMI 36 (SD=6) kg/m2. Of enrolled participants, 105 randomized to the Choice arm, 102 to the Control arm. In the Choice arm, 61 (58%) chose the low-carbohydrate diet and 44 (42%) chose the low-fat diet. Only three low-carbohydrate and two low-fat diet participants switched diets at 12 weeks. Final measurements were collected in 175 (85%) participants, 87 (83%) in the Choice arm and 88 (86%) in the Control arm. For the primary outcome, mean weight loss at 48 weeks was -4.2% of original weight in the Choice participants and -5.3% in Control participants (difference 1.1, 95% CI 0.0 - 2.2, p=0.06). For the secondary outcome, adherence to diet, preliminary descriptive analyses showed that adherence was quite similar between the Choice and Control arms, with mean percent deviation from goal ranging from 7-10% at the 4 time points (12, 24, 36, 48 weeks) in both arms and differing by only 0.6% (10.7 vs 10.1% deviation, respectively) at week 48. Mean IWQOL-Lite total score was similar in both groups at week 48 (Choice 81.7, Control 82.9, difference -1.3, 95% CI -4.5 - 2.0, p=0.4).
The commonly held notion that we should allow patients to choose a diet approach to follow, because multiple diet approaches are effective for weight loss and choosing would enhance adherence, did not bear true in a randomized trial. Future research should consider targeting diet to patient based on metabolic, genetic or other characteristics that might predict improved outcomes.
External Links for this Project
NIH ReporterGrant Number: I01HX000263-01A1
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DRA: Other Conditions
DRE: Treatment - Comparative Effectiveness
MeSH Terms: none