Effects of reduced-fat diets consumed ad libitum on intake of nutrients, particularly antioxidant vitamins

Objectives To determine whether a reduced-fat diet consumed ad libitum can achieve the recommended intakes of other macronutrients, fiber, and cholest erol and whether such a diet affects intake of other important micronutrien ts such as fat-soluble vitamins. Design Twelve-month, randomized, controlled trial of a reduced-fat, ad Libi tum diet vs usual diet. Subjects One hundred ten adults older than 40 years with glucose intoleranc e (2-hour blood glucose concentration=7.0 to 11.0 mmol/L) who were selected from a previous workforce survey. Intervention Monthly small-group meetings aimed at identifying sources of d ietary fat and ways to reduce fat consumption. Main outcome measures Nutrient intakes derived from 3-day food diaries at t he beginning and end of the study. Blood levels of retinol, cr-tocopherol, and beta carotene at the end of the study. Statistical analyses performed Unpaired t tests for determining changes in nutrient intake and antioxidant vitamin concentrations. Separate analyses w ere conducted with users of mineral and vitamin supplements and people who changed smoking status to reduce potential confounding. Results Fat intake decreased from 35% to 26% of energy in the reduced-fat d iet group compared with a 2% decrease in the control group (P<.0001). Total energy intake also decreased in the 2 groups (-362 vs -59 kcal/day, P<.02) . Those changes were reflected in a 3.1+/-4.7 kg (mean+/- standard deviatio n) weight loss in the intervention group compared with a 0.4+/-3.0 kg weigh t gain in the control group (P<.0001). There were no differences between gr oups in the changes in micronutrient intakes, except for an energy-adjusted increase in beta carotene intake in the reduced-fat diet group. Serum reti nol and a-tocopherol concentrations were not different between the groups, but the reduced-fat diet group had higher beta carotene concentrations (P=. 009). Applications A reduced-fat, ad libitum diet can be prescribed to improve ov erall macronutrient intake and achieve modest weight loss without sacrifici ng micronutrient intakes.