Participants
From September 2018 to April 2021, study participants were recruited on a rolling basis from two Foodtown, two Super Foodtown and two Brooklyn Harvest supermarkets in Manhattan, Brooklyn, and Queens, all associated with Allegiance Retail Services and carrying the same food items. Shoppers were recruited in the stores by research assistants standing next to posters and by advertisements posted in the store and on store receipts. Study participants were compensated $55.50 for the initial medical screening visit, which included $5.50 to cover a round trip Metropolitan Transit Authority (MTA) fare, and $90.50 for subsequent visits, which also included a round trip MTA fare.Of the 255 shoppers screened for eligibility, 134 participants were enrolled and randomized into one of the intervention groups. The other 121 participants either did not meet the inclusion criteria, dropped out of the study prior to randomization, or were withdrawn from the study. Of the randomized participants, 7 dropped out or were withdrawn prior to receiving the intervention and 38 after receiving the intervention. The attrition rate up to the study midpoint was 34% (45/134). Dropouts and withdrawals were largely due to the COVID-19 pandemic and included: moving from the area, a 7-month institutional study pause due to the pandemic, discomfort with returning to the hospital after the hiatus, and a change in shopping behavior resulting in noncompliance. Those who dropped out did not differ significantly in sex, age, or assigned intervention group from the others. Twenty-two participants were excluded from the analysis due to noncompliance or missing data. The final number of participants included in this interim analysis was 64, including 19 in the control group, 25 in the 15% discount group, and 20 in the 30% discount group (