Applying the transtheoretical model to eating behaviour change: challengesand opportunities

This review provides a rigorous investigation of the question of whether th e transtheoretical model (TTM) (or stages of change model) is applicable to eating behaviour change. The TTM is currently the most popular of a number of stage theories being used to examine health behaviour change. Stage the ories specify an ordered set of 'stages of readiness to change' into which people can be classified and identify the factors that can facilitate movem ent from one stage to the next. If eating behaviour change follows a stage process, then nutritionists could identify the predominant stage or stages in a population and focus resources on those issues most likely to move peo ple to the next stage (e.g. from no intention of changing, to thinking abou t changing). In addressing this question, the review draws on the defining characteristics of stage theories as clarified by Weinstein et al. (1998), provides an in-depth coverage of methodological considerations, and a detai led summary table of dietary studies applying the TTM. Specific recommendat ions are made for improving the accuracy of dietary stage classifications. Among the key conclusions are: (1) dietary studies using the TTM have been hampered by a focus on nutritional outcomes such as dietary fat reduction, rather than clearly understood food behaviours (e.g. five servings of fruit and vegetables per day); (2) accurate stage classification systems are pos sible for food-based goals, but major misclassification problems occur with nutrient-based goals; (3) observation of an association between stage and dietary intake is not sufficient to demonstrate the validity of the model f or dietary behaviour; (4) there is a need for valid questionnaires to measu re all aspects of the TTM, and more research on the whole model, particular ly the 'processes of change', rather than on single constructs such as 'sta ge'; (5) cross-sectional studies generally support the predicted patterns o f between-stage differences in decisional balance, self-efficacy, and proce sses of change; (6) studies which test the key hypothesis that different fa ctors are important in distinguishing different stages are rare, as are pro spective studies and stage-matched interventions. Only such studies can con clusively determine whether the TTM is applicable to eating behaviour. Sinc e the ultimate test of the TTM will be the effectiveness of stage-matched d ietary interventions, the review ends by exploring the requirements for suc h studies.