A clinical trial to selectively change dietary fat and/or energy intake in women: the Women's Diet Study.

Dietary fat and energy intake have been implicated in breast cancer etiology. To examine the relative importance of these dietary factors on markers of cancer risk in women, we designed an intervention trial to selectively decrease fat and/or energy intake in free-living, premenopausal women who were somewhat overweight. The study used a 2 x 2 factorial design to evaluate the independent and interactive effects of dietary fat and energy. The diets were nonintervention, low fat (15% of energy from fat, maintenance of energy intake), low energy (25% energy reduction), and combination low fat and low energy. We utilized an individualized counseling approach with self-selection of foods. Women on the low-fat and combination diets were asked to meet given daily goals for fat grams and food group exchanges, while women on the low-energy diet used only food group exchanges. Of the 113 premenopausal women randomized who were eligible for analysis, 43% were African-American. A total of 88 women completed the 12-week program, and adherence to the dietary goals was similar in both racial groups. Women on the low-fat diet were able to reduce dietary fat intake to 19% of energy by 4 weeks and to 17% by 12 weeks with a slight decrease in energy intake. Women on the low-energy diet met their energy reduction goals by four weeks while maintaining percentage of energy from fat. Women on the combination diet largely met their goals by four weeks as well. These data indicate that it is possible to selectively manipulate dietary fat and energy intake in women over a short period of time, which makes clinical studies on the relative effects of these two dietary variables on cancer risk biomarkers readily feasible.