Effectiveness Trial of a Dissonance-Based Obesity Prevention Program (Project Health)

• Body Fat Percentage [ Time Frame: Changes in body fat from baseline to 2-year follow up ] [ Designated as safety issue: No ]
  We will use air displacement plethysmography (ADP) via the Bod Pod S/T to assess % body fat. Two measures will be averaged. Body density, calculated as body mass divided by estimated body volume, is used to calculate age- and gender-adjusted body fat percentile scores, based on normative reference data (McCarthy et al., 2006). A pilot validity study (N = 30) revealed that direct DEXA measures of % body fat correlates much more strongly with ADP estimates of body fat (r = .88) than with BMI (r = .23). Change in age- and gender-adjusted body fat percentile over the 2-year follow-up will be the primary outcome. This assessment takes 3-5 minutes to complete.
  
  

• Eating Pathology [ Time Frame: Baseline and post intervention (6 weeks); 6/12/24 month follow-up ] [ Designated as safety issue: No ]
  The Eating Disorder Diagnostic Interview, a brief semi-structured interview, will assess eating disorder symptoms. It provides diagnoses for anorexia nervosa, bulimia nervosa, and binge eating disorder, which will allow us to exclude participants with these disorders. It also provides a continuous measure of overall eating disorder symptoms.
  
  
• Negative Affect [ Time Frame: Baseline and post intervention (6 weeks); 6/12/24 month follow-ups ] [ Designated as safety issue: No ]
  The 20-item Negative Affect subscale of the Positive and Negative Affect Schedule (PANAS: Watson et al., 1988) measures general negative affectivity and depressive symptoms. Using a Likert rating system, participants choose their degree of endorsement of negative affectivity items such as "disgusted with self" and "lonely" (response options: 1 = not at all; 5 = extremely).
  
  
• Food Craving/Liking [ Time Frame: Baseline, 6 weeks (post intervention), 6/12/24 month follow ups ] [ Designated as safety issue: No ]
  The 28-item Food Craving Inventory (FCI; White et al., 2002) assesses subjective cravings for individual foods (pasta, ice cream), asking: "Over the past month, how often have you experienced a craving for the food?"
  
  

• Weighing Habits [ Time Frame: Baseline and post intervention (6 weeks); 6/12/24 mo follow-ups ] [ Designated as safety issue: No ]
  Participants will be asked how often they weighed themselves "in the past two weeks" at each assessment.
  
  
• Physical Activity [ Time Frame: Baseline and post-intervention (6 weeks); 6/12/24 month follow-ups ] [ Designated as safety issue: No ]
  Accelerometers will give objective measures of physical activity from each participant at each wave assessment.
  
  

Aim 1 will test the hypothesis that Project Health significantly reduces increases in % body fat relative to the Healthy Weight intervention and video control condition during a 2-yr follow-up; secondary outcomes are BMI, depressive symptoms and eating disorder symptoms. The investigators will also compare Healthy Weight to video controls.

Aim 2 will test the hypothesis that Project Health participants will experience increased cognitive dissonance (an uncomfortable psychological state) regarding eating unhealthy foods and engaging in sedentary behaviors, and that changes in dissonance mediate the program's weight gain prevention effects. The investigators will also test whether reduced calorie intake and increased physical activity mediate the effects of Project Health on change in % body fat.

Aim 3 will test the hypothesis that intervention effects are amplified for participants with elevated body dissatisfaction (which should increase motivation change) and preference for consistency (which should maximize dissonance induction) and mitigated for participants who report emotional eating and substance use (because these factors increase risk for overeating).