A randomized controlled trial testing the effects of a positive front-of-pack label with or without a physical activity equivalent label on food purchases

Abstract

Background: Positive front-of-pack (FOP) labels, including Singapore's Healthier Choice Symbol (HCS), target a subset of healthier products whose consumption is to be encouraged. However, this may inadvertently lead to excess caloric intake, which could be addressed by including an additional label identifying calories per serving. We test this hypothesis by adding a Physical Activity Equivalent (PAE) label, an indicator of calorie content, to all products available in an on-line grocery store.

Methods: We conducted a randomized controlled trial using a 3 arm within-subject crossover design in adult Singapore residents recruited online. Participants shopped once in each condition in an experimental online grocery store in random order: 1) no FOP label (Control); 2) Select products displaying HCS labels (HCS-only); 3) Condition 2 with additional information displaying PAEs per serving on every product (HCS+PAE). 117 participants were recruited and data from 317 shops were analyzed. We used first-differenced regressions to assess the impact of the conditions on calories per serving (primary) and on other measures of diet quality.

Results: The HCS-only condition led to a statistically significant five-percentage point increase in the proportion of HCS products purchased (95% CI, 1%: 9%). However, neither the HCS-only (3.45; 95% CI, -12.52: 19.43) nor HCS + PAE (8.14; 95% CI, -5.25: 21.54) condition led to a change in the number of calories per serving purchased or changes in other measures of diet quality.

Conclusions: Positive labels, like the HCS, are likely to increase purchases of labelled products. However, these changes may not lead to improvements in diet quality or calorie intake. Combining positive labels with additional PAE information does not appear to address this concern.

Trial registration: ClinicalTrials.gov NCT04172337.

Keywords: Calories; Diet; Front-of-pack label; Nutrition label; Online grocery store; Physical activity equivalent.