Examination of the transtheoretical model (TTM) on fruit and vegetable intake.

摘要

Nutrition researchers are becoming increasingly interested in using the Transtheortical Model to study dietary change. This model has been popular in addictions research for 20 some years, with smoking cessation being most extensively researched. This two-phase dissertation project was designed to tackle some of the limitations discovered in a review of existing applications of the model in dietary change. Phase I was a longitudinal mail survey study with responses collected at baseline, one month, and six months. At baseline, 197 completed and returned the survey (response rate = 40%) while the number dropped to 107 and 77 at one month and six months, respectively. Measures included, two staging algorithms, a stages-of-change questionnaire, a decisional balance scale, a self-efficacy scale, a processes-of-change scale, and a food frequency questionnaire. The measures were adapted from previous research and data verifying their reliability and validity were reported. Major statistical methods used included factor analysis, cluster analysis, analysis of variance (ANOVA) with Scheffe's test, student and paired t-tests, and chi-square test. A three-stage schema (i.e., unconcerned, exploring, and action-oriented) with possible subgroupings was suggested for fruit and vegetable intake. Differences in decisional balance and the use of experiential processes of change appeared to differentiate the unconcerned and exploring stages, whereas the exploring and action-oriented stages differed more in self-efficacy, the use of behavioral processes of change, and the intake of fruits and vegetables. These findings warrant further validation. Phase II was an Internet-based intervention study, comparing a stage-tailored and a nontailored intervention as well as a no-intervention control. One hundred and ten eligible individuals were recruited at baseline (response rate = 51%) and randomly assigned to the study groups. Attrition occurred at the one-month and six-month follow-ups with no differentiations seen by study group. Measures validated in Phase I were adopted and data were examined using ANOVA with Scheffe's test and multivariate ANOVA with Bonferroni's correction. Unfortunately, few intervention effects were detected; strategies that could improve the intervention effectiveness were suggested.