Effect of restaurant menu labelling on consumer food choices: A randomised controlled trial in South India.

India implemented a menu labelling regulation for restaurants with at least ten outlets or a five-star certification in 2022. We conducted a parallel, four-arm, randomised controlled trial to evaluate the impact of menu labelling on consumers' food choices in two chain restaurants in an Indian metropolitan city. We recruited 2462 adult diners (40% female, mean age 36.6 years) exiting the restaurants. We randomised them to receive a control menu or one of three menus labelled with: quantitative nutrient information, interpretational guidance, or contextual guidance. Participants ordered first from the usual restaurant menu (pre-intervention) and then from the labelled menus (post-intervention). We compared the calories, fat, added sugar, and salt content of the post-intervention meal orders in each intervention arm with the control arm using ANCOVA-based gamma generalised linear models, adjusted for pre-intervention values. Since we observed heterogeneity in effects between restaurants for calories, we present the results stratified by restaurants. In Restaurant 2, all three labelling formats significantly reduced calories compared to control - interpretational guidance (ratio of means - 0.88, 95% CI 0.81-0.95), contextual guidance (0.89, 95% CI 0.82-0.96) and quantitative labels (0.90, 95% CI 0.83-0.97). Interpretational guidance reduced the fat (0.94, 95% CI 0.88-0.99) ordered. There was no observable effect on added salt and sugar. About 87% of participants reported that labels were understandable, and 63% reported that labelling influenced their food choices. Menu labelling, particularly interpretational guidance, reduces calories and fat ordered, though effects vary by settings. TRIAL REGISTRATION CLINICAL TRIALS REGISTRY: India: CTRI/2024/05/067074.