Health Promotion and Healthier Products Increase Vending Purchases: A Randomized Factorial Trial.

BACKGROUND: The current food environment has a high prevalence of nutrient-sparse foods and beverages, most starkly seen in vending machine offerings. There are currently few studies that explore different interventions that might lead to healthier vending machine purchases.

OBJECTIVE: To examine how healthier product availability, price reductions, and/or promotional signs affect sales and revenue of snack and beverage vending machines.

DESIGN: A 2×2×2 factorial randomized controlled trial was conducted.

PARTICIPANTS/SETTING: Students, staff, and employees on a university campus.

INTERVENTION: All co-located snack and beverage vending machines (n=56, 28 snack and 28 beverage) were randomized into one of eight conditions: availability of healthier products and/or 25% price reduction for healthier items and/or promotional signs on machines. Aggregate sales and revenue data for the 5-month study period (February to June 2015) were compared with data from the same months 1 year prior. Analyses were conducted July 2015.

MAIN OUTCOME MEASURES: The change in units sold and revenue between February through June 2014 and 2015.

STATISTICAL ANALYSES PERFORMED: Linear regression models (main effects and interaction effects) and t test analyses were performed.

RESULTS: The interaction between healthier product guidelines and promotional signs in snack vending machines documented increased revenue (P<0.05). Beverage machines randomized to meet healthier product guidelines documented increased units sold (P<0.05) with no revenue change. Price reductions alone had no effect, nor were there any effects for the three-way interaction of the factors. Examining top-selling products for all vending machines combined, pre- to postintervention, we found an overall shift to healthier purchasing.

CONCLUSIONS: When healthier vending snacks are available, promotional signs are also important to ensure consumers purchase those items in greater amounts. Mitigating potential loss in profits is essential for sustainability of a healthier food environment.