Do dose, fidelity, and quality of implementation predict participant outcomes? A process evaluation of the PROACTIVE trial
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The systematic evaluation of effective health behavior interventions is critical for addressing overweight and obesity. Process evaluation assesses whether critical intervention components are delivered as intended and can enhance our understanding of program effects by linking participant program exposure to outcomes. The purpose of this study was to conduct a process evaluation of PROACTIVE, an intervention program to prevent and reduce obesity in clinical settings, and to explore associations between measures of dose, fidelity, and session quality with participant outcomes in an effort to explain gender differences in PROACTIVE program response observed at 24 months. Overweight and obese men (n = 74) and women (n = 175) were randomized into the 24-month health behavior counselling intervention. Outcomes of waist circumference (WC) and physical activity (PA; 7-Day PA Recall) were measured at 12 and 24 months. Process outcomes were distilled from Session Summary Forms completed by Health Educators after each session. Dose was a significant predictor of WC (β = -.12, p < .01) and PA (β = -.16, p < .05) at 24 months. Fidelity predicted 12 month WC (β = -.11, p < .05) and PA (β = .21, p < .05). Quality was significantly associated with 12 month (WC: β = .07, p < .05; PA: β = -.18, p < .01) and 24-month outcomes (WC: β = .10, p < .01; PA: β = -.15, p < .05). No gender differences were found for complete program adherence (dose; p = .51) or treatment implemented (fidelity; p = .06). Men and women were exposed to a similar amount of PROACTIVE session content and maintained similar levels of adherence throughout the 24-month intervention, therefore the difference in program success between men and women could not be attributed to unequal program exposure between the two groups. Insight yielded into the relationship between program exposure and participant outcomes via this process evaluation can help guide and refine future program implementation along with providing areas for future research.