Socioeconomic position and the influence of food portion size on daily energy intake in adult females: two randomized controlled trials

Abstract

Background: Reducing portion sizes of commercially available foods could be an effective public health strategy to reduce population energy intake, but recent research suggests that the effect portion size has on energy intake may differ based on socioeconomic position (SEP). Objective: We tested whether the effect of reducing food portion sizes on daily energy intake differed based on SEP. Methods: Participants were served either smaller or larger portions of food at lunch and evening meals (N = 50; Study 1) and breakfast, lunch and evening meals (N = 46; Study 2) in the laboratory on two separate days, in repeated-measures designs. The primary outcome was total daily energy intake (kcal). Participant recruitment was stratified by primary indicators of SEP; highest educational qualification (Study 1) and subjective social status (Study 2), and randomisation to the order portion sizes were served was stratified by SEP. Secondary indicators of SEP in both studies included household income, self-reported childhood financial hardship and a measure accounting for total years in education. Results: In both studies, smaller (vs larger) meal portions led to a reduction in daily energy intake (ps