Investigating the Proximity Effect in a Competitive Food Environment: A study protocol

Obesity and overweight levels are rising nationally, despite recent governmental advertising campaigns being implemented to tackle the prevalence rise at a population level. Therefore, alternative approaches should be investigated in an effort to reduce obesity prevalence rises. One such approach modifies the external cues and the environment where decisions about food are made, and it is commonly known as Choice Architecture (CA). The proximity effect is a strategy within CA that could reduce overall calorie consumption by placing healthier foods at relatively closer distances compared to unhealthy foods. Amongst studies examining the proximity effect, only one so far has explored the simultaneous presentation of healthy and unhealthy foods, referred to as a competitive food environment. As unhealthy foods are often preferred over healthy foods, the current study aims to investigate whether food choice can be overridden by varying degrees of proximity effect and whether key factors such as visual salience, perceived effort, BMI, age, food preference, and executive function moderate this effect. A sample of 48 undergraduate students will participate in a laboratory experiment, believing they are taking part in a relaxation study. Participants will be simultaneously presented with two bowls of food: A healthier fruit selection and an unhealthier chocolate option, each varying according to proximity (either 20cm or 70cm). The participants will be asked to complete a questionnaire measuring multiple factors that may influence food consumption, such as perceived effort and hunger level. The primary outcome of the study is the amount of each food consumed (in grams) depending on relative proximity, with the secondary outcome exploring whether the effect of the latter is influenced by the key moderators. The proposed study explores the proximity effect in a competitive food environment, an area rarely explored in research but high in real-world applicability. If a greater amount of the most proximal food is consumed in each condition, regardless of food healthiness, the intervention can be scaled up to a novel field experiment to further evaluate the effectiveness of the proximity effect in reducing calorie intake.