Predictors of dietary change and maintenance in the Women's Health Initiative Dietary Modification Trial.

Objective: To identify predictors of dietary change to and maintenance of a low-fat eating pattern (<20% energy from fat, > or = 5 servings fruits/vegetables daily, and > or = 6 servings grains daily) among a cohort of postmenopausal women. Candidate predictors included intrapersonal, interpersonal, intervention program characteristics, and clinical center.

Design: Longitudinal study within the Women's Health Initiative Dietary Modification Trial. Dietary change was evaluated after 1 year of participation in the Women's Health Initiative Dietary Modification Trial, and dietary maintenance after 3 years.

Subjects: Postmenopausal women aged 50 to 79 years at baseline who were randomized to the intervention arm of the Women's Health Initiative Dietary Modification Trial (n=19,541).

Statistical Analysis: Univariate and multivariate linear regression analysis was performed and associations evaluated between candidate predictors and each of the three dietary goals: percent energy from fat, fruit/vegetable servings, and grain servings.

Results: Year 1 (change) predictors of percent energy from fat (P<0.005) included being younger (beta=2.12; 70 to 79 years vs 50 to 59 years), more educated (beta=-.69; college vs high school), more optimistic (beta=-.07), attending more sessions (beta=-.69), and submitting more self-monitoring records (beta=-.74). At year 3 (maintenance), the predictors of percent energy from fat (P<0.005) included attending more sessions (beta=-.65) and submitting more self-monitoring scores (beta=-.71). The analytic model predicted 22% of the variance in fat intake at year 1 and 27% at year 3 (P<0.01).

Conclusions: The strongest predictors of dietary change and maintenance were attending intervention sessions and self-monitoring dietary intake. Novel was the finding that optimism predicted dietary change.