Computer-Delivered Intervention for Individuals With Obesity and Elevated Anxiety Sensitivity
Phase: NA
Conditions: Obesity, Anxiety Sensitivity, Eating, Physical Activity
Sponsor: University of Houston

Computer-Delivered Intervention for Individuals with Obesity and Elevated Anxiety 
Sensitivity 
Study Protocol and Statistical Analysis Plan 
NCT03917901 
IRB Approval Date: 02/19/2019 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Study Protocol 
Recruitment. Participants were recruited nationwide through advertisements and physician 
referrals. Recruitment techniques included electronic media (university listservs, Facebook, etc.) 
and flyers in community-based organizations (university settings, community health centers). 
 
Procedures. Interested participants were directed to an online survey which included 
demographic and selected eligibility screening questions (e.g., height/weight to calculate BMI 
and ASI-3) that took approximately 10 minutes to complete. Individuals who were eligible at the 
pre-screen and willing to participate in the study were contacted and emailed an online baseline 
assessment, wherein full eligibility was assessed. During the baseline assessment, informed 
consent was obtained. The participant then completed an approximately 45-minute pre-
intervention online survey that further evaluated eligibility criteria (i.e., re-evaluated 
height/weight and ASI-3) as well as assessed psychological and health-related constructs of 
interests. Participants who did not meet eligibility criteria were provided with referrals and 
compensated $10 in the form of an electronic gift card. Participants who met eligibility criteria 
were randomly assigned to complete either the (a) Anxiety sensitivity (AS) reduction program 
(AS Training [AST]) or (b) Health Information Control (HC); both took approximately 30 
minutes to complete. Following the completion of the randomly assigned program, participants 
were redirected to a 5-minute post-intervention survey and asked to provide qualitative 
information regarding what they learned from the intervention. Participants were then 
compensated $20 in the form of an electronic gift card upon completing the baseline surveys and 
randomly assigned program. Participants were then emailed an online assessment to complete 1-
week, 2-weeks, and 1-month post-intervention to assess relevant psychological and health-
related constructs of interest. The post-intervention online assessments took approximately 45 
minutes (each) to complete. Participants were compensated with $20 in electronic gift cards for 
completing each of the follow-up assessments for up to $80 in electronic gift cards for 
completing the entirety of the study.    
 
Interventions: 
AST. The AS training was adapted from Schmidt et al. (2007). The intervention provided 
descriptions on AS and the effects of AS on the body as well as obesity-related health behavior 
correlates. The intervention included both audio and visual aspects to portray the relevant 
information. The intervention first provided psychoeducational information on AS For example, 
participants were provided explanations as to what AS is and how it may manifest among 
individuals through a number of different scenarios. Participants were then provided 
psychoeducational information regarding relations between AS and obesity-related health 
behavior correlates (e.g., how AS influences eating behaviors and exercise avoidance). To 
illustrate, participants were provided information regarding how eating in response to AS may 
reinforce the belief that eating is an effective affect-regulatory strategy, further perpetuating this 
maladaptive behavior. As a result, this may lead to greater calories consumed and subsequent 
weight gain. Finally, concrete evidenced-based strategies to facilitate motivation and action steps 
for changing AS taken from previous work (i.e., interoceptive exposure; Schmidt et al., 2007; 
Schmidt & Trakowski, 2004) were incorporated into the intervention. Specifically, participants 
engaged in rapid breathing techniques (i.e., hyperventilating) in session and were encouraged to 

practice multiple times and track their levels of distress. Participants were also provided 
information regarding additional interoceptive exposures they could practice outside of the 
intervention on their own time. 
 
Control PFI. Participants assigned to the control group received a computer-delivered 
intervention for general health care that adapted materials from previous control conditions 
utilized in AS reduction trials (Marcus et al., 1999; Marcus et al., 2005; Smits et al., 2016). 
Specifically, the control condition received information on health-related care including, but not 
limited to, outdoor safety (e.g., wearing sunscreen, staying hydrated), improving communication 
with medical care providers, and regular attendance to doctor appointments. However, 
participants did not receive any recommendations or education on mood, dietary, or physical 
habits (e.g., exercise, physical activity). 
 
Statistical Analysis Plan 
 
The equivalence of the random assignment of groups regarding key baseline 
characteristics (e.g., demographics, baseline mental and physical health) and retention at each 
follow-up (i.e., 1-week, 2-week, 1-month; 0 = missed and 1 = completed) were assessed. 
Differences between key baseline characteristics were assessed for participants who completed 
all follow-ups (coded 0) versus participants who missed at least one follow-up (coded 1). Next, 
zero-order correlations among study variables were examined. Latent growth curve (LGC) 
analyses were conducted using Mplus version 8.2 using robust maximum likelihood. Multiple 
imputation using 1,000 imputed datasets calculated in Mplus were used to handle missing data. 
LGC modeling was used to evaluate the overall trajectories across time of: (1) AS, (2) emotional 
eating, (3) expectancies of eating to manage negative affect, and (4) exercise self-efficacy. A 
conditional model was then specified to examine the impact of treatment (0 = HC, 1 = AST) on 
the slope factor for each of the stated outcome variables.  
 
For all analyses, shape factors were set for the slope to be centered at the baseline 
assessment and the 1-month follow-up was fixed at 1.0. The 1-week and 2-week follow-up were 
freely estimated. The variances of the intercept and slope factors were also freely estimated. 
LGC analysis model fit was evaluated with the following fit indices: root-mean-square (RMSEA; 
Steiger, 1990) and standardized root-mean-square residual (SRMR; Jöreskog & Sörbom, 1996) 
with values below .08 indicating acceptable fit (Little, 2013), Tucker-Lewis index (TLI; Tucker 
& Lewis, 1973) and comparative fit index (CFI; Bentler, 1990) with values at .90 or above 
indicating acceptable fit (Little, 2013).