Point-of-sale sugar-sweetened beverage warning posters v . control posters were associated with reductions in school store sugar-sweetened beverage purchases made by Guatemalan adolescents

OBJECTIVE: We examined whether point-of-sale warning posters, compared with control posters, reduced Guatemalan adolescents' purchases of sugar-sweetened beverages (SSB) at school stores. DESIGN: We used a difference-in-differences approach (4-week baseline and 4-week treatment). Our primary analysis compared two schools assigned to an intervention warning poster to one school that displayed a control poster. Based on purchase transaction data, the outcomes were volume of SSB, beverage kcal and sugar purchased per transaction. SETTING: Three private schools in Guatemala City, Guatemala. PARTICIPANTS: Students between 12 and 18 years of age. RESULTS: Our primary analysis found that the warning poster decreased the overall volume of SSB (in ounces) that adolescents purchased in the warning poster intervention schools (-2·27 oz. 95 % CI = (-2·70, -1·85)) compared with the control school. This reduction was driven by a decrease in SSB purchases (OR = 0·64, 95 % CI = (0·49, 0·86)). The warning posters were associated with a significant reduction in likelihood of purchasing a beverage with kilocalories (calories) (OR = 0·68, 95 % CI = (0·49, 0·92)). These changes were associated with a significant overall decrease in sugar purchased (-5·54 g 95 % CI = (-6·69, -4·39)). The posters were associated with a significant increase in non-SSB purchases in the intervention schools compared with the control school (OR = 1·53, 95 % CI = (1·16, 2·02)). CONCLUSION: Our results suggest that messages that warn adolescents about the high-sugar content in SSB may be an effective, low-cost way to modestly reduce purchases of these drinks. These findings provide evidence to support national front-of-package labelling, currently being considered in Guatemala.