As noted yesterday in When Costs Rise, Sales of Unhealthful Foods Drop, so-called sin taxes on unhealthful foods may help stem America’s obesity and diabetes epidemics.

Facing critical budget deficits, some city and state legislators are embracing the idea. Earlier this month, Philadelphia Mayor Michael Nutter proposed a tax on soda purchases, while Colorado Gov. Bill Ritter last month signed a bill to tax candy and soda.

“State-level taxes exist on soda sold in grocery stores and vending machines in 34 and 39 states, respectively, and the mean taxes, currently applied for revenue generation, range from 3% to 4%,” write San Francisco Department of Public Health officials Mitchell H. Katz, MD, and Rajiv Bhatia, MD, in an editorial published in Monday’s edition of Archives of Internal Medicine.

But there’s not much evidence to support a link between such modest surcharges and changes in consumer behavior, they note.

“More substantial surcharges may decrease the consumption of sweetened beverages and, equally important, increase the consumption of more healthful alternatives,” write Drs. Katz and Bhatia.

The revenues cities and states collect “could be used to increase awareness about the harm of sugar-sweetened beverages and fund structural interventions, such as creating water stations in schools,” they add. “Copying a successful tactic of anti-tobacco crusaders, the funds also could be used to counter the lavish advertising of soda and junk food or for ‘marketing’ ordinary tap water.

“In the end,” they conclude, “putting our money where our mouth is means aligning our economic incentives so that we always serve up the healthful choice.”  

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Adults tend to consume less pizza and soda when prices increase, and their body weight and overall calorie intake also appear to decrease, according to a report in yesterday’s edition of Archives of Internal Medicine.

“To compensate for food environments where healthful foods (i.e., fresh fruits and vegetables) tend to cost more, public health professionals and politicians have suggested that foods high in calories, saturated fat or added sugar be subject to added taxes and/or that healthier foods be subsidized,” the authors write as background information in the article. “Such manipulation of food prices has been a mainstay of global agricultural and food policy, used as a means to increase availability of animal foods and basic commodities, but it has not been readily used as a mechanism to promote public health and chronic disease prevention efforts.”

Between 1985 and 2005, a 10% price increase was associated with a 7% decrease in calories consumed from soda and a 12% decrease in calories consumed from pizza, according to lead researcher Kiyah J. Duffey, PhD, and colleagues at the University of North Carolina, Chapel Hill.

A $1 increase in the cost of soda or pizza was also associated with a lower overall daily calorie intake, lower body weight and improved insulin resistance score. A $1 increase in the cost of both soda and pizza was associated with even greater changes.

The researchers estimate an 18% tax on these foods would result in a decline of roughly 56 calories per person per day—the equivalent of 5 pounds per person per year—with corresponding reductions in the risk of obesity-related diseases.

“In conclusion, our findings suggest that national, state or local policies to alter the price of less healthful foods and beverages may be one possible mechanism for steering U.S. adults toward a more healthful diet,” the authors write. “While such policies will not solve the obesity epidemic in its entirety and may face considerable opposition from food manufacturers and sellers, they could prove an important strategy to address overconsumption, help reduce energy intake, and potentially aid in weight loss and reduced rates of diabetes among U.S. adults.”

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