Considering Patient Diet Preferences to Optimize Weight Loss (DietChoice)

Obesity is increasingly common and can lead to decreased quality of life, increased medical and psychiatric illness, high health care costs, and early mortality. The problem of obesity is as great in veterans as it is in the general public. Adherence to dietary therapy for obesity is often inadequate, possibly because patients' food preferences are not considered during dietary counseling. Allowing patients to choose a diet based on their food preferences may increase their motivation to adhere to diet counseling. This, in turn, could enhance their weight loss success and, ultimately, reduce the many health complications and costs of obesity. The proposed study will examine whether assessing a person's food preferences, and then allowing the person to choose from two commonly prescribed diets, results in greater weight loss success.

The prevalence of obesity (body mass index [BMI] 30 kg/m2) in US adults has skyrocketed over the past 30 years, and is currently as high or higher in veterans as it is in non-veterans. 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. Yet, 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. It is widely felt, but not empirically shown, that targeting the diet to an individual's food preferences will enhance adherence, thereby improving weight loss outcomes. This study will test the commonly proposed assumption that helping patients choose a diet based on their dietary preferences will increase weight loss success relative to assigning or recommending one diet. 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 from two of the most widely studied diets for weight loss, either a low-carbohydrate, calorie-unrestricted diet (LCD) or a low-fat, reduced-calorie diet (LFD). This choice will be informed by results from a validated food preference questionnaire and a discussion of available diet options with trained personnel. As may occur in the clinical setting, 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. The Choice intervention is designed to enhance the three psychological needs of a person according to self-determination theory (SDT): competence, relatedness, and, in particular, autonomy. This should maximize intrinsic motivation, thereby improving adherence to diet recommendations and increasing weight loss. 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 SDT constructs of autonomy orientation, competence, and relatedness. If assisting patients to choose their diet enhances adherence and increases weight loss, the results will support the provision of diet options to veterans and non-veterans alike, and bring us one step closer to remediating the obesity epidemic faced by the VA and other healthcare systems.

obesity, diet, low carbohydrate, diet, fat-restricted, food preferences, quality of life, patient compliance

Participants are allowed to choose between a low-carbohydrate or a low-fat diet for weight loss after receiving information about these diets and their food preferences (Choice arm). Then they receive counseling on their chosen diet in a small group format. The low-carbohydrate diet limits carbohydrate intake to 20-40 grams/day initially. The low-fat diet restricts saturated fat to below 30% of daily calories and has a 500-1000 calorie deficit. Group sessions are every 2 weeks for 24 weeks then alternate with telephone calls every 2 weeks for 24 weeks. Phone calls focus on goal setting to maximize weight loss. Participants also receive counseling on behavioral techniques and physical activity. Participants in this arm have the option to switch diets at 12 weeks.

Participants are randomly assigned to (rather than getting to choose, as in the experimental arm) a low-carbohydrate or a low-fat diet for weight loss (Control arm). Then they receive counseling on their chosen diet in a small group format. The low-carbohydrate diet limits carbohydrate intake to 20-40 grams/day initially. The low-fat diet restricts saturated fat to below 30% of daily calories and has a 500-1000 calorie deficit. Group sessions are every 2 weeks for 24 weeks then alternate with telephone calls every 2 weeks for 24 weeks. Phone calls focus on goal setting to maximize weight loss. Participants also receive counseling on behavioral techniques and physical activity. Participants in this arm do not have the option to switch diets at 12 weeks.

Participants are allowed to choose between a low-carbohydrate or a low-fat diet for weight loss after receiving information about these diets and their food preferences (Choice arm). Then they receive counseling on their chosen diet in a small group format. The low-carbohydrate diet limits carbohydrate intake to 20-40 grams/day initially. The low-fat diet restricts saturated fat to below 30% of daily calories and has a 500-1000 calorie deficit. Group sessions are every 2 weeks for 24 weeks then alternate with telephone calls every 2 weeks for 24 weeks. Phone calls focus on goal setting to maximize weight loss. Participants also receive counseling on behavioral techniques and physical activity. Participants in this arm have the option to switch diets at 12 weeks.

Participants are randomly assigned to (rather than getting to choose, as in the experimental arm) a low-carbohydrate or a low-fat diet for weight loss (Control arm). Then they receive counseling on their chosen diet in a small group format. The low-carbohydrate diet limits carbohydrate intake to 20-40 grams/day initially. The low-fat diet restricts saturated fat to below 30% of daily calories and has a 500-1000 calorie deficit. Group sessions are every 2 weeks for 24 weeks then alternate with telephone calls every 2 weeks for 24 weeks. Phone calls focus on goal setting to maximize weight loss. Participants also receive counseling on behavioral techniques and physical activity. Participants in this arm do not have the option to switch diets at 12 weeks.

Diet Adherence as Measured by Block Food-frequency Questionnaire (Absolute Percentage Deviation From the Goal Macronutrient Intake--<30% Fat for Low-fat Diet or <10% Carbohydrate for Low-carbohydrate Diet)

Change in Obesity-specific Health-related Quality of Life as Measured by Impact Of Weight On Quality Of Life-Lite (IWQOL-Lite) Questionnaire From Baseline to 48 Weeks

change in obesity-specific health-related quality of life as measured by Impact Of Weight On Quality Of Life-Lite (IWQOL-Lite) Questionnaire total score from baseline to 48 weeks Minimum 0 Maximum 100 Higher score means better

Inclusion Criteria: Body mass index 30 or greater Stable health Desire to lose weight Agrees to attend regular visits Access to telephone and reliable transportation Has a Veterans Affairs Medical Center (VAMC) provider Exclusion Criteria: Certain chronic or unstable disease (kidney or liver disease, type 1 diabetes, hemoglobin A1c 12% or more, insulin use, unstable heart disease, transplant recipient, blood pressure 160/100 or greater, fasting blood triglycerides 600 or greater, LDL cholesterol 190 or greater) Pregnancy, breastfeeding, lack of birth control Active dementia, psychiatric illness, or substance abuse (past year) Weight loss therapy in previous month Pacemaker or defibrillator Enrolled in another study that might affect measurements Previously in study of low-carbohydrate or low-fat diet for weight loss Unable to complete all study measures

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