Impact of increasing vegetarian availability on meal selection and sales in cafeterias.

Abstract

Shifting people in higher-income countries towards more plant-based diets would protect the natural environment and improve population health. Research in other domains suggests altering the physical environments in which people make decisions (“nudging”) holds promise for achieving socially desirable behaviour change. Here we examine the impact of attempting to nudge meal selection by increasing the proportion of vegetarian meals offered in a year-long large-scale series of observational and experimental field studies. Anonymised individual-level data from 94,644 meals purchased in 2017 were collected from three cafeterias at an English university. Doubling the proportion of vegetarian meals available from 25% to 50% - e.g. from 1 in 4 to 2 in 4 options - increased vegetarian meal sales (and decreased meat meal sales) by 14.9 and 14.5 percentage points in the observational study (two cafeterias) and by 7.8 percentage points in the experimental study (one cafeteria), equivalent to proportional increases in vegetarian meal sales of 61.8%, 78.8% and 40.8% respectively. Linking sales data to participants’ previous meal purchases revealed that the largest effects were found in the quartile of diners with the lowest prior levels of vegetarian meal selection. Moreover serving more vegetarian options had little impact on overall sales and did not lead to detectable rebound effects: vegetarian sales were not lower at other mealtimes. These results provide novel and robust evidence to support the potential for simple changes to catering practices to make an important contribution to achieving more sustainable diets at the population level.