Kelly Brownell, who directs the Rudd Center for Food Policy and Obesity at Yale University, is a longtime proponent of the fat tax as a solution to the obesity epidemic. “The principle is simple,” he wrote in an email to The Daily Beast. “Cigarettes, alcohol, and some foods have negative consequences and hence high health-care costs, and taxes are a way of recovering some of these costs. Consumption goes down as taxes go up.”

But some experts warn that these so-called “sin taxes” can present a classic conflict of interest for the state, even if they always result in additional revenue…

There’s another problem with sin taxes, like levies on tobacco and junk food: they tend to be regressive, because poorer people spend more of their income on food relative to wealthier people.

But Brant Hellwig, a professor of taxation at Washington and Lee School of Law, said: “If the revenue from a junk-food tax were dedicated to expanding health-insurance coverage among low-income individuals, then what may appear to be a regressive tax on the revenue-collection side would be far less so when both sides of the equation are considered.”