Living together-does it help or hinder the pursuit of a healthful diet, physical activity, and weight loss among cancer survivors and their chosen partners?

Purpose: Parental or spousal cohabitating relationships are often targeted in behavioral interventions, but the contribution of cohabitation is poorly understood. This study explored whether cohabitation status moderated the impact of social cognitive theory constructs on adiposity, diet, and exercise in a dyadic, web-based weight loss intervention among cancer survivors and their chosen partners.

Methods: The 24-week weight loss intervention was conducted among 56 dyads, comprised of a cancer survivor and their chosen partner (n = 112). Baseline and 6-month data on social cognitive theory constructs (self-efficacy, social support, and perceived barriers), and study outcomes of adiposity (weight and waist circumference), diet (calories and diet quality), and moderate-to-vigorous physical activity (MVPA) were used to perform moderated-mediation analyses among cohabitating (n = 25) versus non-cohabitating (n = 31) dyads.

Results: The intervention was positively associated with dietary social support (path a: 0.36, 95% CI [0.083, 0.659]) and inversely associated with perceived dietary barriers (path a: - 10.57, 95% CI [- 19.109, - 3.091]) and perceived exercise barriers (path a: - 11.29, 95% CI [- 22.098, - 3.500]) among those who did not cohabitate (effects not observed among cohabitating pairs). The intervention's mediating effects through perceived barriers on weight (indirect effect (ab): - 2.21, 95% CI [- 4.794, - 0.548]), waist circumference (ab: - 1.13, 95% CI [- 2.452, - 0.171]), caloric intake (ab: - 5.09 (2.86), 95% CI [- 12.602, - 0.709]), and self-reported MVPA (ab: 0.29 (0.18), 95% CI [0.019, 0.754]) also were stronger among non-cohabitating pairs.

Conclusions: These findings suggest that social support partners outside the home substantially enhance intervention impact, though relationship quality and gender dynamics warrant further exploration.

Trial Registration: ClinicalTrials.gov Identifier: NCT04132219.