Study design for a clinical trial to examine food price elasticity among participants in federal food assistance programs: A laboratory-based grocery store study

We present a protocol for a study investigating the effect of food price changes on purchasing decisions among individuals participating in federal food assistance programs and among those not participating in these programs. We use a laboratory-based grocery store design, which provides greater control over factors influencing food purchasing than in situ experiments in actual grocery stores. We focus primarily, but not exclusively, on eggs because they are highly nutritious, easy to prepare, can be included in many different dishes, and are a part of a wide range of cultural food menus. The primary aim of this study is to compare the own-and cross-price elasticity of eggs between individuals participating in federal food assistance programs and those not participating in these programs. Our secondary aims are to 1) compare the own- and cross-price elasticity of eggs between overweight/obese individuals and non-overweight/obese individuals, 2) examine whether delay discounting moderates the effect of income on own- and cross-price elasticity, 3) examine whether subjective social status moderates the effect of participation in federal food assistance programs on the purchase of high nutrient-dense foods, and 4) examine whether usual psychological stress level moderates the effect of subjective social status on the purchase of high-nutrient dense foods. The results of this study will provide information about the drivers of food demand among low-income adults. A better understanding of these drivers is needed to develop effective nutrition interventions for this large population.