Naming Matters: Prompting Smaller Portions in an Online RCT

Abstract

Introduction: Large portions, which can lead people to eat more, are becoming increasingly common in U.S. restaurants. This study tested whether portion-size descriptions on menus and different pricing strategies influence the selection of smaller portion sizes.

Study design: This was a 4 × 2 between-subjects online randomized controlled experiment.

Setting/participants: This was an online simulated menu-ordering study conducted in 2021 among 2,205 U.S. adults.

Intervention: Adults viewed a fast-casual and full-service menu with entrées available in 2 sizes and ordered an entrée from each. Participants were randomized to view 1 of 4 portion-size descriptors (smaller/larger portion): (1) no descriptor/large (control), (2) standard/large, (3) just right/large, and (4) no descriptor/hearty. Participants were also randomized to either linear (i.e., reduced price=50% larger portion's price) or nonlinear pricing (i.e., reduced price=70% larger portion's price) (4 × 2 factorial design).

Main outcome measures: In 2022, logistic regression models were used to analyze whether the interventions increased the likelihood of choosing a reduced portion.

Results: Regardless of pricing scheme, participants in the standard/large condition selected reduced portions by 10 (95% CI=0.04, 0.16) and 13 (95% CI=0.07, 0.18) percentage points more than those in the control condition (fast-casual and full-service menus, respectively). Selection of reduced portions in the just right/large condition increased by 9 (95% CI=0.04, 0.15) and 8 (95% CI=0.02, 0.14) percentage points. For the fast-casual menu, keeping portion-size descriptors constant, participants ordered a reduced portion by 5 percentage points more with nonlinear pricing than with linear pricing.

Conclusions: Portion-size descriptions on restaurant menus, even with nonlinear pricing, are a low-cost strategy to promote the selection of lower-calorie, smaller portions without restricting choice.