Extent of reporting of external validity elements in childhood obesity prevention interventions: A literature review

Background: Available evidence does not support effective approaches to preventing childhood obesity, despite its increasing prevalence. Enhancing the amount of external validity information in research reports could improve our understanding of the potential generalizability and relevance of intervention results and aid future evidence-based reviews. To assess the extent to which these issues are reported in the childhood obesity prevention literature, we reviewed recent intervention reports and evaluated whether external validity dimensions were included. Methods: Controlled, long-term (> 1 yr) childhood obesity prevention trials, published between 1980 and 2004 and that included a behavioral target of physical activity and/or healthy eating along with body mass index or body fat changes were identified. External validity criteria developed by Green and Glasgow (2006) were applied to this review. Nineteen studies met screening criteria and were evaluated (1 family-based intervention, 18 school-based programs). Results: Generalizability and dissemination elements were generally lacking in these studies. Most infrequent were reports of setting-level selection criteria (11%) and representativeness characteristics (0%), implementation of intervention content (26%), program costs (0%), and whether the program was sustained long-term (0%). By contrast, many elements more related to internal validity were frequently included such as selection criteria and participant attrition. Conclusions: Enhancing the reporting of contextual and generalizability elements can improve the future evidence base to support the translation and dissemination of childhood obesity prevention intervention research. Discussion will include practical hurdles that need to be addressed to improve the design and reporting of these external validity elements.