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

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.

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

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

Students, staff, and employees on a university campus.

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.

The change in units sold and revenue between February through June 2014 and 2015.

Linear regression models (main effects and interaction effects) and t test analyses were performed.

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.

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.