Psychosocial constructs were not mediators of intervention effects for dietary and physical activity outcomes in a church-based,lifestyle intervention: Delta Body and Soul III

Authors: Thomson, Jessica; TUSSING-HUMPHREYS, LISA - University Of Illinois; ZOELLNER, JAMIE - Virginia Tech; Goodman, Melissa

Submitted to: Public Health Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2015
Publication Date: 1/22/2016
Publication URL: http://handle.nal.usda.gov/10113/61919
Citation: Thomson, J.L., Tussing-Humphreys, L.M., Zoellner, J.M., Goodman, M.H. 2016. Psychosocial constructs were not mediators of intervention effects for dietary and physical activity outcomes in a church-based,lifestyle intervention: Delta Body and Soul III. Public Health Nutrition. 19(11):2060-9. doi: 10.1017/S1368980015003602.

Interpretive Summary: Given the well-known health disparities present in minority populations, particularly African American adult populations, logical first steps to resolving these inequities include improving the diet of African American adults as well as increasing their physical activity levels. In general, the most successful diet and physical activity interventions have been those that are based on health behavior theory. However, while the efficacy of such interventions are tested, an evaluation of the theoretical basis of the intervention is less often reported. Hence the purpose of this study was to determine if effects from a theory-based, multicomponent educational intervention were mediated by changes in the psychosocial constructs – decisional balance (weighing of good and bad aspects of a behavior), self-efficacy (skill and confidence building), and social support (physical or emotional comfort given by family and friends). Delta Body and Soul III, conducted in 2011 and 2012, was a 6-month, church-based, diet and supervised physical activity intervention designed to improve diet quality and increase physical activity in rural, Southern, primarily African American adults. Churches were recruited from 4 counties in the Lower Mississippi Delta region of the United States. Primary outcomes included diet quality and physical activity. Mediation analyses were conducted to determine if significant indirect effects of the intervention were present via the 3 psychosocial constructs. Results from the mediation models indicated that there was no evidence that intervention treatment indirectly influenced changes in diet quality or physical activity through its effects on decisional balance, self-efficacy, and social support. Hence, despite using a theory-based design, the psychosocial constructs targeted and measured in Delta Body and Soul III did not appear to be the mechanisms by which this intervention influenced changes in diet quality and physical activity. This study highlights the importance of moving beyond simply establishing the success of an intervention to determining the characteristics of an intervention that contributed to the behavior changes observed.

Technical Abstract: Background: While using theory-based methods when designing and implementing behavioral health interventions is essential, it also has become increasingly important to evaluate an intervention’s theoretical basis. Such evaluations can be accomplished through the use of mediation analysis which can inform design modifications and improvements to produce more effective interventions. Hence the purpose of this study was to determine if effects from a multicomponent educational intervention were mediated by changes in the psychosocial constructs – decisional balance, self-efficacy, and social support. Methods: Guided by the Transtheoretical Model of Behavior Change and the construct of social support, Delta Body and Soul III, conducted from August 2011 to May 2012, was a 6-month, church-based, diet and supervised physical activity intervention designed to improve diet quality and increase physical activity in rural, Southern, primarily African American adults. Churches (5 intervention and 3 control) were recruited from 4 counties in the Lower Mississippi Delta region of the United States. Primary outcomes, diet quality and aerobic and strength/flexibility physical activity, as well as psychosocial constructs, were assessed via self-report, interviewer administered surveys at baseline and at 6 months post intervention. Mediation analyses were conducted using ordinary least squares (continuous outcomes) and maximum likelihood logistic (dichotomous outcomes) regression path analysis. Results: Retention rates for the intervention and control groups were 76% (219/287) and 84% (102/122), respectively. Based upon results from the multiple mediation models, there was no evidence that treatment (intervention vs. control) indirectly influenced changes in diet quality or physical activity through its effects on decisional balance, self-efficacy, and social support. However, there was evidence for direct effects of social support for exercise on physical activity and self-efficacy for sugar-sweetened beverages on diet quality. Conclusions: Results from this study do not support the hypothesis that the psychosocial constructs – decisional balance, self-efficacy, and social support – were the theoretical mechanisms by which the Delta Body and Soul III intervention influenced changes in diet quality and physical activity. This study highlights the importance of moving beyond simply establishing an intervention’s efficacy to determining the aspects of an intervention that contributed to the behavior changes observed.