An ad libitum, very low-fat diet results in weight loss and changes in nutrient intakes in postmenopausal women

Objectives To determine whether a very low-fat diet (<15% of energy intake) consumed ad libitum during an 8-month period can achieve weight loss of 5% to 10% of initial body weight while still providing adequate intakes of other essential nutrients. Design Longitudinal, 8-month, ad libitum, free living, very low-fat diet trial. Subjects Fifty-four of the sixty-four healthy postmenopausal women recruited completed the entire study (age 59 +/- 8 years, BMI = 29.6 +/- 6.3). Twenty-four of these women used hormone replacement therapy, thirty women did not. Intervention Weekly sessions aimed at teaching and reinforcing a very low-fat intake diet for eight months. Main outcome measures Body weight, percent body fat, waist-to-hip ratio, resting energy expenditure, respiratory quotient, and nutrient intakes derived from 7-day food records at the beginning and at 2, 4, 6, and 8 months of the study. Statistical analysis performed Repeated measures analysis of variance and Tukey post hoc analysis were used to analyze significant differences in mean data (P<.05). Results Fat intake decreased from 33.2 +/- 7.5% to 11 +/- 4% over the 8-month intervention period (P<.00001). Weight loss was 6.0 kg +/- 4.2 kg (P<.000038), an 8% weight change, and decrease in percent body fat of 2.7% +/- 0.2% (Pless than or equal to.000046). Weight correlated better with the self-reported fat intake (r=0.321, P<.01) than the energy intake (r=0.263, P<.05) at baseline. Fiber intake increased from 16 g +/- 0.6 g to 23 g +/- 0.2 g (P<.0005). All micronutrient intakes remained at or above preintervention ranges, except for a decrease in vitamin E intake from 8.1 mg +/- 4.0 mg to 3.7 mg +/- 1.1 mg (P<.0005) on the very low-fat diet and linoleic acid from 6.3% +/- 1.5% to 2.5% +/- 0.7% (P<.000001) with no significant reduction in linolenic acid. Hormone replacement was not associated with the amount of weight loss. Applications This study demonstrates that adherence to a very low-fat diet consumed ad libitum causes weight loss in the 5% to 10% range and a reduction of body fat. These reductions, along with the observed decreases in fat intake, are associated with improved health outcomes. Because of the decreased vitamin E and n-3 fatty acid intake, emphasis on foods high in these nutrients may need to be encouraged for those consuming a very low-fat diet.