Partner Weight Loss and Diet Outcomes at 24 Months in a Randomized Controlled Trial of a Dyadic Versus Individual Weight Management Intervention

ABSTRACT Background Including romantic partners as supports in behavioral weight management programs targeting index participants could yield spillover effects, but few studies have explored the effects on partners. Methods Dyads included an index participant with BMI ≥ 27 kg/m 2 and a cohabitating partner with BMI ≥ 18 kg/m 2 randomized to a participant‐only ( N = 116) or partner‐assisted ( N = 115) intervention. All index participants received an evidence‐based group weight management program. Partners in the partner‐assisted group attended half of the sessions but were not required to make behavioral changes/lose weight. Linear mixed models compared changes in partner weight and self‐reported caloric intake between groups at 24 months. Results Most partners identified as male (63%) and White (88%). Mean baseline weight and BMI were 98 kg (SD 28.1) and 32 kg/m 2 (SD 7.8), respectively. At 24 months, partners in the partner‐assisted versus participant‐only group lost more weight (−2.5 kg vs. −0.4 kg; estimated mean difference: −2.0 kg [95% CI −3.5, −0.6]). There were no differences in caloric change (partner‐assisted: −367 kcal, participant‐only: −196 kcal; estimated mean difference: −171 kcal [95% CI −358, 17]). Conclusions Involving romantic partners is an efficient weight management approach that generates meaningful long‐term weight loss for cohabitating partners despite them not being the direct targets for weight loss. Trial Registration Clinicaltrials.gov NCT03801174