1. Introduction
obesity, cancer, PA behaviors, adiposity, reductions in dietary barriers, weight loss, 543 cancer, DUET
OBESITY, CANCER, SECONDARY, ADIPOSITY, REGRESSION
Mechanisms that explain behavior change within web-based lifestyle interventions are not well-studied. This secondary analysis explores whether the effects of the DUET web-based lifestyle intervention on diet, physical activity, and/or adiposity are mediated through changes in self-efficacy, social support, and perceived barriers (key constructs of social cognitive theory). Data on mediators, diet quality, caloric intake, moderate-to-vigorous physical activity (MVPA), weight, and waist circumference (WC) were analyzed from 112 cancer survivors and their partners enrolled in the DUET intervention. Mediation analyses were performed using Mplus to execute regression analyses and determine associations. Mediation analyses supported an effect of the intervention on caloric intake (−3.52, 95% CI [−8.08 to −0.84]), weight (−1.60, CI [−3.84 to −0.47]), and WC (−0.83, CI [−1.77 to −0.18]), interpreting these negative associations as intervention induced reductions in dietary barriers. Higher social support was significantly and positively associated with, but not a mediator for, improvements in self-reported and accelerometry-measured MVPA (b = 0.69, CI [0.19, 1.24]) and (b = 0.55, CI [0.15, 1.00]), respectively. Self-efficacy did not appear to mediate the intervention’s effects. Findings suggest that the effects of the DUET intervention on diet and adiposity stem from reducing perceived barriers to a healthful, low-calorie diet.More people are surviving cancer due to improvements in early cancer screening and advancements in reliable and effective treatments [As with the prevalence of cancer survivorship, obesity rates in the U.S., as well as among cancer survivors, are also growing [Over the past decade, many multi-behavioral interventions have been implemented among cancer survivors to improve diet and PA behaviors and target weight loss [For instance, the FRESH START trial, a personally-tailored mailed print diet and PA intervention conducted among 543 cancer survivors, was informed by the SCT and reported improvements in self-efficacy for diet as a key mediator for long-term increases in vegetable and fruit (V&F) consumption and decreases in fat intake at 2-year follow-up [The interest of cancer survivors is shifting towards online programs to gain health information [To date, very few studies have identified the SCT-mediating processes through which multi-behavior web-based interventions change health behavior among cancer survivors. Therefore, evaluating constructs that have been shown to be effective in improving diet and PA behaviors in previous, more traditionally delivered interventions is key to understanding behavior change using this newer technology. To address this gap, the current study explores whether the effects of the DUET web-based lifestyle intervention on diet, MVPA, and/or adiposity are mediated through SCT constructs (self-efficacy, social support, and perceived barriers to diet and exercise). We hypothesize that the previously reported [