A METHOD TO ACHIEVE CONTROL OF DIETARY MACRONUTRIENT COMPOSITION IN AD-LIBITUM DIETS CONSUMED BY FREE-LIVING SUBJECTS

Objective: To validate a shop system in controlling macronutrient comp osition during ad libitum dietary intervention. Design: Six months ran domized intervention trial. Setting: A shop at the department from whi ch all foods were collected free of charge and registered by a purpose -designed computer system. Subjects: Sixty-five free-living obese subj ects (25 kg/m(2) < BMI < 34 kg/m(2)) recruited through advertisement a nd from a waiting list at the Department. Total drop-out rate was 8%. Interventions: Ad libitum low-fat diets (30 energy-% (E%) fat): (1) Hi gh-protein (25 E% protein, HP) or (2) Low-protein, (12 E% protein, LP) or habitual diet (controls, C). Main outcome measures: Compliance was assessed by 24 h urinary nitrogen excretion (24 h UN). Results: After one month of dietary intervention 24 h UN increased significantly in the HP group and decreased significantly in the LP group (Group differ ence 95% CI):6.8 g (5.0-8.7 g), P < 0.0001). This group difference rem ained throughout the trial. There was good agreement between protein i ntake as estimated by the shop computer and as estimated from 24 h UN in both first (r = 0.86) and second half of the intervention (r = 0.80 ). Conclusion: The high dietary compliance demonstrates the potential of this method to control macronutrient composition in ad libitum diet ary intervention studies in free-living subjects.