Coaction in multiple behavior change interventions: consistency across multiple studies on weight management and obesity prevention.

Objective: Coaction refers to the extent to which taking action on one behavior increases the odds of taking action on a second behavior. This integrative study examines the generalization of coaction in three studies on weight-related behaviors.

Method: Data from three randomized trials of tailored interventions (n = 1,277, n = 1,800, and n = 6,000) were examined to determine if coaction of behavior change occurred differentially in treatment and control groups. In each analysis, the likelihood of progressing to the Action or Maintenance stages for the target behaviors was evaluated using logistic regression.

Results: Despite differences in populations, targeted behaviors, levels of tailoring in interventions, and timing of follow-up assessments, 17 out of 24 (70.8%) logistic regressions revealed significant coaction in the treatment group as opposed to only three out of 24 (12.5%) in the control condition. In 23/24 analyses, coaction of behavior change was larger on an absolute basis in the treatment group. Individuals in the treatment group progressing to Action/Maintenance for one behavior were 1.4-5 times more likely to make progress on another behavior compared to those in the treatment group who did not make such progress on the first behavior.

Conclusions: This study demonstrates that despite considerable variability in study design, coaction reliably occurs more in the presence of Transtheoretical-Model based multiple behavior change interventions. Additional studies are needed to replicate these results in other behavioral areas and to examine the predictors of differential coaction. The ability to consistently create coaction within multiple behavior interventions can increase the efficacy and cost-effectiveness of multiple behavior change interventions.