Validation of the 2 x 24 Hour Recall method and a 7-day Web-based food diary against doubly labeled water in Danish adults

The European Food Safety Authority has suggested that EU countries implement the 2x24-hour diet recall (2x24hDR) method and physical activity (PA) measurements for national dietary surveys. Since 2000, Denmark has used 7-day Food Diaries (7dFD) with PA questionnaires and measurements. The accuracy of the two diet and PA methods was evaluated by comparing reported energy intakes (EI), and pedometer-determined step counts, and self-reported time spent in moderate-to-vigorous PA (MVPA) during leisure with total energy expenditure measured by the Doubly Labelled Water technique (TEE_DLW), and with PA energy expenditure (PAEE), respectively. 52 male and 68 female volunteers aged 18-60 years were dosed with DLW on the first day of a 4-week study period. They were randomly assigned to start with either the 24hDR or the web-based 7dFD, wore a pedometer for the first 7 days, and filled in a step diary. The mean TEE_DLW (11.5MJ/d) was greater than the mean reported EI for the 7dFD (9.5 MJ/d (P<0.01) but the same as the 2x24hDR (11.5MJ/d). The mean under-reported EI was -16% (7dFD) and 0% (2x24hDR) and the proportion of under-reporters was either 34% (7dFD) or 4% (2x24hDR). Most participants evaluated the 7dDR as more flexible and comprehensive, despite altering participants eating habits. Pearson’s correlation between steps corrected for cycling and PAEE was r=0.44 P<0.01. Spearman’s correlation for self-reported hours spent in MVPA and PAEE was r=0.58 P<0.01. The 2x24hDR perform better than the existing 7dFD method. Pedometer-determined steps and self-reported MVPA can be considered good predictors of PAEE in adult Danes.