Stages of change for reducing dietary fat intake over 18 months

Abstract

Objective: To describe the stages of change that take place over 18 months, using the criterion of fat intake < or = 30% of total energy to define effective action and to investigate the effect of a single dietary feedback report on dietary fat reduction.

Design: Subjects were randomly assigned to experimental or control conditions and assessed at 0, 6, 12, and 18 months for fat intake and stage of change. Subjects in the experiment group received 1 feedback report at baseline; all subjects received a report at 12 months.

Subjects: Potential subjects (n = 614) were recruited by mail from a random sample of nonsmoking adults (32% response rate). Subjects were excluded if consuming < or = 30% of energy from fat or if pregnant or lactating (n = 145). Although 83% of subjects (n = 389) completed the 18-month study, only 296 provided complete data for all time points. The study was restricted to these 296.

Intervention: Dietary feedback reports plus brief educational materials were provided following the experiment design.

Analyses: Repeated measures analysis of variance with fat intake (percent of energy from fat) as the dependent variable and baseline stage and condition as independent variables. In addition, t tests were used to compare groups at specific time points.

Results: There was a main effect for time (F3,286 = 39, P < .0001) and baseline stage (F3,286 = 24, P < .0001), but no effect of feedback. There was a time-by-feedback interaction (F4,286 = 4.7, P < .01). There was a short-term effect of feedback over 6 months (t = 3.8, P < .001), but this effect was not significant at other time points. About 9% to 12% of subjects in the precontemplation or contemplation stages, 24% of subjects in the preparation stage, and 40% of unclassified subjects at baseline progressed to the action stage by 18 months. Between 12 and 18 months, subjects progressing at least 1 stage reduced their fat intake to a greater extent than subjects who failed to progress (t = 5.1, P < .0001).

Implications: Interventions targeted to stage of change have the potential for accelerating the rate of change for dietary fat reduction, but reaching the goal of fat intake < or = 30% of total energy may require more intensive interventions than a single dietary feedback report.