Effect of snack-food proximity on intake in general population samples with higher and lower cognitive resource

Jennifer A Hunter,Gareth J Hollands,Dominique-Laurent Couturier,Theresa M Marteau

doi:10.1016/j.appet.2017.11.101

Abstract

ObjectivePlacing snack-food further away from people consistently decreases its consumption (“proximity effect”). However, given diet-related health inequalities, it is important to know whether interventions that alter food proximity have potential to change behaviour regardless of cognitive resource (capacity for self-control). This is often lower in those in lower socio-economic positions, who also tend to have less healthy diet-related behaviours. Study 1 aims to replicate the proximity effect in a general population sample and estimate whether trait-level cognitive resource moderates the effect. In a stronger test, Study 2 investigates whether the effect is similar regardless of manipulated state-level cognitive resource. MethodParticipants were recruited into two laboratory studies (Study 1: n = 159; Study 2: n = 246). A bowl of an unhealthy snack was positioned near (20 cm) or far (70 cm) from the participant, as randomised. In Study 2, participants were further randomised to a cognitive load intervention. The pre-specified primary outcome was the proportion of participants taking any of the snack. ResultsSignificantly fewer participants took the snack when far compared with near in Study 2 (57.7% vs 70.7%, β = −1.63, p = 0.020), but not in Study 1 (53.8% vs 63.3%, X2 = 1.12, p = 0.289). Removing participants who moved the bowl (i.e. who did not adhere to protocol), increased the effect-sizes: Study 1: 39.3% vs 63.9%, X2 = 6.43, p = 0.011; Study 2: 56.0% vs 73.9%, β = -2.46, p = 0.003. Effects were not moderated by cognitive resource. ConclusionsThese studies provide the most robust evidence to date that placing food further away reduces likelihood of consumption in general population samples, an effect unlikely to be moderated by cognitive resource. This indicates potential for interventions altering food proximity to contribute to addressing health inequalities, but requires testing in real-world settings. Trial registrationBoth studies were registered with ISRCTN (Study 1 reference no.: ISRCTN46995850, Study 2 reference no.: ISRCTN14239872).

Highlights

Populations of lower, compared with higher, socio-economic position (SEP) consume more energy-dense foods
Given the cognitive effort required to translate health information into sustained behaviour change, differences in cognitive resource by SEP could explain the evidence that information-based interventions may contribute to diet-related health inequalities
The current studies build on existing literature: first, by estimating the magnitude of the proximity effect in larger general population samples, including those with lower education level, by replicating and extending an existing study conducted in a smaller university student sample (Maas et al, 2012), and second, by providing preliminary evidence for whether the proximity effect is moderated by cognitive resource

Summary

Introduction

Populations of lower, compared with higher, socio-economic position (SEP) consume more energy-dense foods SEP negatively impacts state-level cognitive resource, with people from lower income groups showing poorer impulse control (Mani, Mullainathan, Shafir, & Zhao, 2013) and greater vulnerability to unhealthy food advertising when under temporary cognitive load (Zimmerman & Shimoga, 2014). Lower cognitive resource, such as EF, is associated with overeating and higher BMI in young people (Groppe & Elsner, 2015; Reinert, Po'e, & Barkin, 2013) and lower quality food choice in adulthood (Cohen, Yates, Duong, & Convit, 2011; Hall, 2012). If interventions that alter environmental cues do not rely on cognitive resource for their impact, they may be less likely to widen existing inequalities and may even reduce them if more effective in those with lower cognitive resource

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