Transtheoretical model-based nutritional interventions in adolescents: a systematic review.

Background: Literature has shown a tendency of inadequate dietary intake among youth, consequently, nutritional interventions are required. The transtheoretical model (TTM) classifies individuals based on their readiness to change. This model is widely used for health education interventions with proven efficacy.

Purpose: This review aimed to weigh the strength of evidence about the TTM usage in nutritional interventions for adolescents and its effectiveness regarding dietary intake.

Methods: This study followed the PRISMA guidelines. Eligible studies were input into Mendeley software. The Adolec, Google Scholar, LILACS, PsycINFO, PubMed, Science Direct and Web of Science databases were searched. Only full original articles written in English, Spanish or Portuguese on randomized controlled trials and quasi-experimental designs that applied the TTM in the design of nutritional interventions targeting adolescents were included, with no restrictions on publication date. The quality and risk of bias was evaluated with the Effective Public Health Practice Project Quality Assessment Tool for Quantitative Studies.

Results: The initial search yielded 3779 results. Three studies were rated as strong, six as moderate and five as weak. The final sample of 14 articles included adolescents that were mostly recruited from schools, with interventions ranging from one month to three years. The TTM was used alone or combined with other behavior-change theories and most of the interventions involved digital technology. The nutritional topics covered included fruit and vegetable consumption, low-fat diet, and cooking skills. Four studies presented improvement in fruit and vegetable consumption and four progressed through stages of change. Participants from two interventions reduced fat intake. At the end of one intervention, all the participants were in action and maintenance stages.

Conclusion: The TTM seems to be a successful strategy for nutritional intervention aiming at improving dietary intake in adolescents. Its application in different contexts shows that the TTM is flexible and possible to be implemented in many settings. The use of the model is shown to be restricted to the stage of change' construct. Further studies should use all constructs of the TTM in the design and compare the TTM with other behavior-change theories to better understand its effectiveness.