Minimizing Random Error in Dietary Intakes Assessed by 24-h Recall, in Overweight and Obese Adults

Objective: To determine the minimum number of days of dietary intake interviews required to reduce the effects of random error (day-to-day variability in dietary intake) when using the multiple-pass, multiple-day, 24-h recall method. Design: Cross-sectional study. Setting: University research department. Subjects: A total of 50 healthy non-smoking overweight and obese (body mass index=26–40 kg/m2) adult men and women aged 39–45 years completed the study. Participants were randomly selected from volunteers for a larger unrelated study. Interventions: Each participant completed 10, multiple-pass, 24-h recall interviews on randomly chosen days over 4 weeks. The minimum number of record days was determined for each macronutrient (carbohydrate, fat, protein) and energy, for each gender, to obtain a 'true' (unobservable) representative intake from reported (observed) dietary intakes. Results: The greatest number of days required to obtain a 'true' representative intake was 8 days. Carbohydrate intakes required the greatest number of days of dietary record among males (7 days), whereas protein required the greatest number of days among females (8 days) in this cohort. Sunday was the day of the week that showed greatest variability in macronutrient intakes. Protein (P<0.05) and fat (P