Background: Although increased consumption of dietary fiber and grain products is widely recommended to maintain healthy body weight, little is known about the relation of whole grains to body weight and long-term weight changes.

Objective: We examined the associations between the intakes of dietary fiber and whole- or refined-grain products and weight gain over time.

Design: In a prospective cohort study, 74,091 US female nurses, aged 38-63 y in 1984 and free of known cardiovascular disease, cancer, and diabetes at baseline, were followed from 1984 to 1996; their dietary habits were assessed in 1984, 1986, 1990, and 1994 with validated food-frequency questionnaires. Using multiple models to adjust for covariates, we calculated average weight, body mass index (BMI; in kg/m(2)), long-term weight changes, and the odds ratio of developing obesity (BMI > or = 30) according to change in dietary intake.

Results: Women who consumed more whole grains consistently weighed less than did women who consumed less whole grains (P for trend < 0.0001). Over 12 y, those with the greatest increase in intake of dietary fiber gained an average of 1.52 kg less than did those with the smallest increase in intake of dietary fiber (P for trend < 0.0001) independent of body weight at baseline, age, and changes in covariate status. Women in the highest quintile of dietary fiber intake had a 49% lower risk of major weight gain than did women in the highest quintile (OR = 0.51; 95% CI: 0.39, 0.67; P < 0.0001 for trend).

Conclusion: Weight gain was inversely associated with the intake of high-fiber, whole-grain foods but positively related to the intake of refined-grain foods, which indicated the importance of distinguishing whole-grain products from refined-grain products to aid in weight control.