Comparing two psychological interventions in reducing impulsive processes of eating behaviour: Effects on self-selected portion size

Abstract

Objective Palatable food, such as sweets, contains properties that automatically trigger the impulse to consume it even when people have goals or intentions to refrain from consuming such food. We compared the effectiveness of two interventions in reducing the portion size of palatable food that people select for themselves. Specifically, the use of dieting implementation intentions that reduce behaviour towards palatable food via top-down implementation of a dieting goal was pitted against a stop-signal training that changes the impulse-evoking quality of palatable food from bottom-up. Design We compared the two interventions using a 2x2 factorial design. Methods Participants completed a stop-signal training in which they learned to withhold a behavioural response upon presentation of tempting sweets (vs. control condition) and formed implementation intentions to diet (vs. control condition). Selected portion size was measured in a sweet-shop-like environment (Experiment 1) and through a computerized snack dispenser (Experiment 2). Results Both interventions reduced the amount of sweets selected in the sweet shop environment (Experiment 1) and the snack dispenser (Experiment 2). On average, participants receiving an intervention selected 36% (Experiment 1) and 51% (Experiment 2) fewer sweets than control participants. In both studies, combining the interventions did not lead to additive effects: Employing one of the interventions appears to successfully eliminate instrumental behaviour towards tempting food, making the other intervention redundant. Conclusions Both interventions reduce self-selected portion size, which is considered a major contributor to the current obesity epidemic.