Researchers from Northwestern University found that a program that replaced Chicago park vending machine choices with healthier snacks, led to increased monthly sales and positive feedback from patrons.

The Chicago Park District is the largest municipal park system in the United States, serving almost 200,000 children annually through after-school and summer programs. The city is also one of the first US cities to improve park food environments through more healthful snack vending through the Chicago Park District's 100 percent Healthier Snack Vending Initiative.

From spring 2011 to fall 2012, researchers collected data through observation, surveys, and interviews on staff and patron acceptance of snack vending items, purchasing behaviors, and machine operations at a sample of 10 Chicago parks. A new snack vending contract included nutrition standards for serving sizes, calories, sugar, fat, and sodium for all items. Fifteen months of snack vending sales data were collected from all 98 snack vending machines in park field houses.

Researchers found that 100 percent of staff and 88 percent of patrons reacted positively to the initiative, and average monthly per-machine sales increased from $84 to $371 during a 15-month period.

The study is published in Preventing Chronic Disease.