Objective: Weight gain occurs during marriage, yet obesity treatment is focused on individuals. Outcomes may be improved by targeting joint weight loss and the interpersonal milieu that fosters spousal interdependence. Self-determination theory (SDT) posits that autonomy-supportive environments (e.g., promote meaningful choice, minimize control) produce better health outcomes. This trial tested an SDT-informed weight-loss intervention intended to facilitate autonomy support in couples.
Method: Sixty-four couples were randomized to standard behavioral weight loss (BWL) that couples attended together or to a SDT-informed weight-loss intervention (SDT-WL) that aimed to bolster autonomy support (AS). Groups met weekly for 6 months with assessments at 0, 3, 6, and 12 months.
Results: Percent weight loss at 6 and 12 months was 10.4% ± 6.5% and 9.2% ± 8.2%. No differences were observed between the BWL and SDT-WL conditions in percent weight loss or changes in AS. Across conditions, higher baseline AS predicted greater weight loss at 6 and 12 months (ps <.001). Increases in AS over time predicted greater weight loss at 6 and 12 months (ps ≤ .02). Post hoc moderation analysis indicated that only participants with low (but not high) baseline AS achieved greater gains in AS at 12 months in SDT-WL than in the BWL conditions (p < .02).
Conclusions: Although no differences were found between conditions on weight loss or changes in autonomy support behavior, autonomy support from one's spouse predicted weight loss in both couples-based weight-loss approaches. For couples with low levels of AS, an SDT-informed approach was effective at increasing this desirable interpersonal behavior. (PsycINFO Database Record (c) 2020 APA, all rights reserved).