Figure 1.

Timeline of the dietary assessment activity in the Lifestyle Validation Study, embedded in the Nurses’ Health Study and Nurses’ Health Study II, United States, 2010–2012. This figure shows the timeline for group 1 participants. Groups 2 and 4 were assigned similar data collection timeline as group 1, except groups 2 and 4 participants were asked to complete the 7-day dietary record (7DDR) in phases II and IV instead. Group 3 went through the same data collection timeline as group 1. Within the same phase, 7DDRs and automated self-administered 24-hour dietary recalls (ASA24s) were completed 2–5 weeks apart (to avoid artificially high correlations). For groups 1 and 3, the ASA24 was completed first, followed by the 7DDR in phase I, but this order was reversed in phase III. For groups 2 and 4, the 7DDR was completed first followed by the ASA24 in phase II, but this order was reversed in phase IV. Additionally, groups 1 and 3 completed the web-based version of the food frequency questionnaire (WebFFQ), which was enhanced by the use of branched questions, approximately 2 weeks before completion of the paper semiquantitative food frequency questionnaire (SFFQ) (the final SFFQ, conducted at the end of the follow-up period), and groups 2 and 4 completed it approximately 2 weeks after completion of the final SFFQ. To minimize alteration in eating behavior, the participants were not told in advance the day that they would be asked to complete the ASA24; days were randomly selected and may or may not have included a weekend day.