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.