The nutritional implications of the consumption of reduced-fat and reduced-sugar foods were assessed in nonobese, free-living female consumers in a 10-wk intervention trial. Subjects in control (C; n = 13), reduced-fat (RF; n = 17), and reduced-sugar (RS; n = 19) groups, all initially nonusers of reduced-fat and reduced-sugar products, kept 4-d food-intake records to establish energy and macronutrient intakes at baseline and at 2,4,7, and 10 wk. Groups RF and RS were instructed to use reduced-fat and reduced-sugar foods, respectively, ad libitum in place of habitually consumed foods with traditional composition, whereas group C was to maintain their usual diet. All foods were purchased by subjects in normal retail outlets and consumed at home. Analyses revealed no main or interactive effect of group on reported energy intake. RF subjects reduced their reported fat intake during the study (P = 0.017) compared with RS and C subjects, and RS subjects reduced their reported sucrose intake compared with RF and C subjects (P = 0.049). Group differences in total sugar intake were not significantly different. All groups reported a small but significant increase in reported protein intake during the study, whereas there were no significant effects on percentage energy from total carbohydrate. Body weights did not change significantly in any group over the study period. These results indicate that, as a single dietary strategy, casual use of macronutrient-substituted foods by consumers under normal eating conditions can significantly influence the macronutrient composition of the diet, but has little net effect on total energy intake or body weight status.