Effects of added-sugar warning labels on restaurant menus in the USA: an online randomised controlled trial

Added-sugar warning labels on restaurant menus have the potential to reduce population-level added-sugar intake. However, the efficacy of specific label designs and labelling thresholds remains unclear. The aim of this study was to test the extent to which two sugar warning labels and two policy-relevant labelling thresholds can influence consumer behaviour.

In an online randomised controlled trial, we recruited a national sample matched to US demographics. Eligible participants (US adults aged ≥18 years who had eaten restaurant food at least monthly in the past year) were randomly assigned (1:1:1:1:1) to a no-label control or one of four label conditions consisting of two factors: label design (a red icon-only label 150% of menu text height or a black icon-plus-text label 100% of text height with the words "SUGAR WARNING") and added-sugar labelling threshold (item contains ≥50% or ≥100% of the Daily Value of added sugar). Participants placed hypothetical orders from fast-food (dinner), full-service (dinner), and café (breakfast) menus. Primary outcomes were grams of added sugar ordered averaged across dinner orders, and for breakfast. This study was registered with ClinicalTrials.gov, NCT06666725, and is complete.

From Dec 23, 2024, to Feb 13, 2025, 15 977 individuals provided consent and were assessed for eligibility. 11 275 individuals met eligibility criteria and were assigned to one of the five study groups: control (n=2252); icon-only with 50% Daily Value threshold (n=2251); icon-only with 100% Daily Value threshold (n=2249); icon-plus-text with 50% Daily Value threshold (n=2252); or icon-plus-text with 100% Daily Value threshold (n=2271). After exclusions due to incomplete or duplicate surveys, failed attention checks, or implausibly quick response times, the analytical sample included 10 456 participants (5534 [52·9%] women and 4876 [46·6%] men). For dinner orders, both warning label designs reduced added sugar ordered compared with the control (icon-plus-text: 10·4 g [11%] reduction [95% CI -13·4 to -7·4], p<0·0001; icon-only: 6·6 g [7%] reduction [-9·6 to -3·6], p<0·0001). Icon-plus-text labels also led to a significantly greater average reduction in added sugar ordered for dinner than icon-only labels (3·7 g [4%] greater reduction; 95% CI 1·3 to 6·2, p=0·0028). For breakfast orders, both warning label designs reduced added sugar ordered compared with the control (icon-plus-text: 2·5 g [5%] reduction [-4·8 to -0·3], p=0·042; icon-only: 3·6 g [7%] reduction [-5·8 to -1·3], p=0·0055), and the label designs performed similarly. No significant differences were found between the labelling thresholds.

Mandating noticeable added-sugar warning labels for restaurant menus is a promising policy option for reducing added sugar ordered from restaurants.

The American Diabetes Association and Bloomberg Philanthropies.