Considering Patient Diet Preferences to Optimize Weight Loss

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.

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