Using a descriptive social norm to increase vegetable selection in workplace restaurant settings

Objective: Recent work has shown that exposure to social norm based messages may enhance the consumption of vegetables. However, the majority of this work has been conducted in laboratories, often with student populations. Little is known about whether this approach can be successfully used in other contexts. In this study, a poster featuring a message based on social norms was tested to examine whether it could increase and maintain the purchase of meals with vegetables in workplace restaurants. Methods: A pretest-posttest design with three phases was used in three workplace restaurants in the United Kingdom. The first two weeks formed the pre-intervention phase, the second two weeks the intervention phase, and the last two weeks the post-intervention phase. During the intervention phase only, posters containing a social norm message relaying information about vegetable purchases of other diners were placed in each restaurant. The main outcome measure was the percentage of meals purchased with vegetables, which was analysed using Pearson’s chi-squared test. Results: Participants were judged to be: male (57%), not overweight (75%) and under the age of 60 (98%). The intervention was positively associated with the percentage of meals purchased with vegetables: baseline vs. intervention (60% vs. 64% of meals purchased with vegetables; p < 0.01); intervention vs. post-intervention (64% vs. 67% of meals purchased with vegetables; p < 0.01); and baseline vs. post-intervention (60% vs. 67% of meals purchased with vegetables; p < 0.001). Conclusions: Social norm messages may increase the purchase of vegetables in a workplace setting.