Evaluating energy intake measurement in free-living subjects: when to record and for how long?

Objective: To nutritionally analyse mean energy intake (EI) from different 3d intervals within a 7d recording Period and to evaluate the seasonal effect on energy and nutrient intake.

Design: Cross-sectional study of dietary intake collected with 7d food diaries.

Subjects: Participants from two long-term trials were pooled. These trials, investigating genetic and environmental influences on body weight, were the Genotyping And Phenotyping (GAP) study and a cohort observational study, Rowett Assessment of Childhood Appetite and metabolism (RASCAL). There were 260 Caucasian adults, BMI range 16.7-49.3 kg/m(2), age range 21-64 years.

Results: Mean EI for Wednesday, Friday and Saturday had the closest approximation to the 7d mean (0.1 % overestimate). A gender x season interaction (p = 0.019) with a different intake pattern for females and males was observed. For females, lower mean (SE) EI was recorded in summer (8117 (610) kJ) and autumn (7941 (699) kJ) compared with spring (8929 (979) kJ) and winter (8132 (1041) kJ). For males, higher mean (SE) EI was recorded in summer (10420 (736) kJ) and autumn (10490 (1041) kJ) compared with spring (9319 (1441) kJ) and winter ((9103 (1505) kJ).

Conclusions: The study results indicate that 3d weighted intakes recorded from Wednesday, Friday and Saturday are most representative of 7d habitual intake in free-living subjects. They also indicate that seasonality has a limited effect on EI and no effect no macronutrient intake.