Cupcake PanicFood activists have told us that artificial sweeteners, meat, trans fat, and carbohydrates are the causes of American obesity. The latest food scare comes from Katie Couric’s film, Fed Up, which claims the obesity epidemic is mainly caused by America’s sugar “addiction”—a purported condition that would seem to afflict Ms. Couric herself. But in case you thought activists had jumped the shark with their latest movie, a new report by researchers at the RAND Corporation shows otherwise.

The report claims the main driver of rising obesity rates is more affordable food, stating “As a share of disposable income, Americans now have the cheapest food available in history, which fueled the obesity epidemic.” Most Americans, however, may not feel that food is cheaper than ever—Federal Reserve data show that food prices have increased faster than prices in general since 2010.

Whether the facts bear out the RAND claims or not, we can surely expect more efforts to push sin taxes on foods activists don’t like to ensure that everybody’s paying “enough” for their daily bread. Whatever the justification, don’t expect the effort to be popular. A recent Associated Press poll found 60 percent opposed to one particular tax. The Danes even passed a tax on Danishes, but a popular revolt of cross-border shopping scuppered the hated levy.

With economic growth anemic and cost-of-living headed upwards, don’t expect the RAND claims to fall on receptive ears. Shoppers’ wallets are already growling.