Abstract
In this thesis the application of the transtheoretical model (Prochaska and DiClemente 1992) to dietary change is investigated. Four studies were conducted examining the core constructs of the model these are (a) stages of change, (b) processes of change, (c) concepts of change. An exploratory cross sectional study found that process and concept use differed significantly between precontemplaters and post action stages. With self efficacy however the main differences were between preparation and other stages. Semi-structured interviews with then conducted with 20 participants in the process of improving their dietary behaviour. Results showed that strategies similar to those outlined in the transtheoretical model social support and consciousness raising were strongly emphasised, regarding decisional balance more benefits than disadvantages were associated with dietary change. Following this a 6-month longitudinal study tested the effectiveness of stage matched and general pamphlets for clients with type two diabetes. 955 participants completed questionnaires with 327 participants receiving stage matched interventions, 309 receiving general interventions and 319 participants being allocated to a control group, intervention copies were distributed at 3 months and a second questionnaire at six months. Significant differences were found between the pre action and post action stages with low fat dietary behaviour. Precontemplaters scored significantly lower than other stages with all processes and with the pros and cons of decisional balance and contemplaters scored lower than post action stages with several processes. Maintainers scored highest in self efficacy. The use of processes and concepts did not match fully that outlined in the transtheoretical model. Interestingly when participants were classified on the basis of low, medium and high fat behaviour, process and concept use followed a broadly linear pattern. At follow up detailed analysis was made problematic by high subject attrition. However, higher scores in consciousness raising were associated with forward stage movement and low scores in social support with retrograde movement. There was no significant difference in effectiveness of stage matched and general pamphlets. There is, however, weak evidence that interventions in general improve low fat dietary behaviour. The stage classification may however give insights not available with standard classifications. Indicating advantages in combining stage and traditional classifications. Suggestions for future studies to investigate the model more thoroughly are also discussed.