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.