DIETFITS Study (Diet Intervention Examining the Factors Interacting With Treatment Success
Condition: Obesity; Insulin Resistance
MeSH terms: Insulin Resistance
Study type: Interventional

Summary: 
      Genomics research is advancing rapidly, and links between genes and obesity continue to be
      discovered and better defined. A growing number of single nucleotide polymorphisms (SNPs) in
      multiple genes have been shown to alter an individual's response to dietary macronutrient
      composition. Based on prior genetic studies evaluating the body's physiological responses to
      dietary carbohydrates or fats, the investigators identified multi-locus genotype patterns
      with SNPs from three genes (FABP2, PPARG, and ADRB2): a low carbohydrate-responsive genotype
      (LCG) and a low fat-responsive genotype (LFG). In a preliminary, retrospective study (using
      the A TO Z weight loss study data), the investigators observed a 3-fold difference in
      12-month weight loss for initially overweight women who were determined to have been
      appropriately matched vs. mismatched to a low carbohydrate (Low Carb) or low fat (Low Fat)
      diet based on their multi-locus genotype pattern. The primary objective of this study is to
      confirm and expand on the preliminary results and determine if weight loss success can be
      increased if the dietary approach (Low Carb vs. Low Fat) is appropriately matched to an
      individual' s genetic predisposition (Low Carb Genotype vs. Low Fat Genotype) toward those
      diets.
    

Detailed description: 
      If the intriguing preliminary retrospective results are confirmed in this full scale study,
      the results will demonstrate that inexpensive DNA testing could help dieters predict whether
      they will have greater weight loss success on a Low Carb or a Low Fat diet. Commensurate with
      increasing scientific interest in personalized medicine approaches to intervention
      development, this would provide an example of the potentially substantial health impacts that
      could be obtained through understanding specific gene-environment interactions that have been
      anticipated from the unraveling of the human genome.

      Mobile App Sub-Study-For the purpose of augmenting adherence to high vegetable consumption in
      both diet groups, we will develop a theory-based mobile app to increase vegetable consumption
      through goal-setting, self-monitoring, and social comparison. Participants from both diet
      groups with iPhones will be re-randomized to receive the app at either months 4-5 or months
      7-8. The first phase during months 4-7 will be used to compare the effect of a mobile app
      (intervention) vs. no mobile app (waiting-list control). The a priori hypothesis is that
      vegetable consumption will increase among those who receive the app in both diet arms. The
      investigator and outcomes assessor will be blinded to group assignment. Intention-to-treat
      analysis will be used.
    

Intervention name(s): Low-Carbohydrate Diet; Low-Fat Diet; Mobile App
Intervention type(s): Behavioral; Behavioral; Behavioral
Intervention description(s): Counseling/instruction on how to follow a low-carbohydrate diet.; Counseling/instruction on how to follow a low-fat diet.; Mobile app to increase vegetable consumption. Participants with iPhones will be re-randomized to receive a mobile app beginning at either months 4-5 or months 7-8. The first phase during months 4-7 will be used to compare the effect of a mobile app (intervention) vs. no mobile app (waiting-list control). The a priori hypothesis is that vegetable consumption will increase among those who receive the app in both diet groups.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Investigator, Outcomes Assessor)
Primary purpose: Treatment