Habit Formation in a Couples-Based Weight Loss Intervention

Background: Weight trajectories mirror each other in couples, and weight-regulating habits may also be interdependent. This study explored 1) interdependence in habit automaticity of self-weighing and exercise in spouses participating in a couples-based weight loss (WL) program and 2) if own or partner habit automaticity predicted WL outcomes. Methods: Participants (n=64 dyads, 50% female, BMI 33.5±5.4 kg/m2, 92.2% White) in a couples-focused WL trial completed the Self-Reported Habit Index Automaticity Subscale and provided objective weight at baseline, 3, 6, and 12 months. Empty dyadic multilevel models with correlated residuals were estimated to examine interdependence in automaticity; then, dyadic models controlling for baseline weight, condition, and baseline habit automaticity were estimated to test whether automaticity predicted weight. Results: 97 participants from 50 dyads provided complete data. Selfweighing and exercise habit automaticity were not correlated within couples at baseline or 6 months but were correlated at 3 months (exercise, p=.02, and a trend for self-weighing, p=.08). Controlling for baseline habit automaticity, own or partner baseline habit automaticity did not predict 3-month WL; however, greater partner self-weighing automaticity at 3 months predicted more WL at 6 months (p=.01). Greater own self-weighing automaticity at 6 months predicted 12-month WL (p=.02). Weight loss was interdependent within couples at all timepoints. Conclusions: This study provides mixed evidence regarding the dyadic nature of habit automaticity in couples attending behavioral WL treatment, yet weight change was interdependent among spouses. More research is needed to understand the behavioral underpinnings of weight co-regulation in couples.