In the latest attempt to counter the growing obesity epidemic, San Francisco supervisor Mark Farrell introduced legislation imposing restrictions on vending machines in order to push the city residents towards healthier diets. The measure comes on the heels of a recent wave of anti-obesity policies, including the soda tax in neighboring Berkeley and calorie-posting and sodium-warning requirements in New York City. Similar to those measures, San Francisco's new policy is well-intentioned but unlikely to have any real impact on obesity.

The proposed policy would limit the types of foods and drinks that can be sold at vending machines on city property. If passed, the policy would ban sodas, candy and chips from these vending machines altogether. Other foods would have to meet stringent low-calorie, low-sugar, low-sodium and low-fat nutritional criteria.

There are two reasons to doubt the measure's effectiveness. First, vending machine restrictions may not actually reduce the amount of calories that people consume. For example, several studies examined the impact of restricting soda in vending machines in schools. They compared the students' access to soda and the amount of soda consumed in states that have implemented soda restrictions and those that have not. They found that while students in states with soda restrictions had less access to soda in school, they did not reduce their overall soda consumption. Instead, they compensated for the restricted soda access by either bringing it with them or drinking more soda outside of school.

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