Defending his proposal to fight obesity by restricting soft drink sizes, New York Mayor Michael Bloomberg says, "I think that's what the public wants the mayor to do." If the public wanted it, of course, there would be no need for the government to require it. Bloomberg's plan makes sense only to the extent that it changes consumers' decisions by limiting their options—specifically, by decreeing that restaurants, food carts, movie theaters, and concession stands at sports arenas may not sell more than 16 ounces of most sugar-sweetened beverages in one cup or bottle. Yet The New York Times reports that Bloomberg cast doubt on the rationale for this rule right out of the gate:

The mayor, who said he occasionally drank a diet soda "on a hot day," contested the idea that the plan would limit consumers' choices, saying the option to buy more soda would always be available. "Your argument, I guess, could be that it's a little less convenient to have to carry two 16-ounce drinks to your seat in the movie theater rather than one 32 ounce," Mr. Bloomberg said in a sarcastic tone. "I don't think you can make the case that we're taking things away."

If so, what's the point? If the added inconvenience of carrying two containers does not deter people from drinking as much soda as they otherwise would, how can Bloomberg possibly claim his restrictions will make people thinner?

The answer is that Bloomberg and his health commissioner, Thomas Farley, say whatever pops into their heads, without regard to logic or evidence. Consider:

In New York City, where more than half of adults are obese or overweight, Dr. Thomas Farley, the health commissioner, blames sweetened drinks for up to half of the increase in city obesity rates over the last 30 years. About a third of New Yorkers drink one or more sugary drinks a day, according to the city. Dr. Farley said the city had seen higher obesity rates in neighborhoods where soda consumption was more common.

Correlation = causation. QED. If that is the quality of Farley's science, perhaps we should not ask how he came up with the estimate that sweetened drinks account for "up to half" of the increase in obesity rates since the early 1980s. That statement, after all, is consistent with the possibility that sweetened drinks account for none of the increase.

Even if we accept Farley's claims about soda's role in rising obesity rates, it does not follow that Bloomberg's plan will have a measurable impact on New Yorkers' waistlines. There are reasons to doubt that it will, starting with the mayor's observation that extra-thirsty customers can always buy another 16-ounce drink (which might actually result in the consumption of more calories, assuming their usual serving is between 16 and 32 ounces). Nor will undercover health inspectors monitor the city's fast food restaurants to prevent diners from availing themselves of free refills; the regulations graciously let them drink as much soda as they want, as long as they do it 16 ounces at a time. The size rule does not apply at all to convenience stores, supermarkets, or vending machines, so Big Gulps, giant Slurpees, and large bottles of soda will still be readily available. Bloomberg also plans to exempt fruit juices, which typically have more calories per ounce than sugar-sweetened soda, and milk-based drinks. So while New Yorkers won't be allowed to order 20 ounces of Coke (240 calories), they will still be able to get a 20-ounce Starbucks whole-milk latte (290 calories) or even a 24-ounce Double Chocolaty Frappuccino (520 calories), not to mention a 20-ounce milkshake (about 800 calories).

In other words, Bloomberg is right when he says there will still be lots of opportunities for New Yorkers to consume large quantities of high-calorie drinks, which means he does not even have a sound paternalistic justification for his meddling. He is screwing with people not to protect them from their own foolish choices but just to create the appearance of doing so. Or maybe just because he can.

The Times notes that Bloomberg "has made public health one of the top priorities of his lengthy tenure" with "a series of aggressive regulations," including "bans on smoking in restaurants and parks" and "a prohibition against artificial trans fat in restaurant food." It adds that "the measures have led to occasional derision of the mayor as Nanny Bloomberg, by those who view the restrictions as infringements on personal freedom." Is there any other reasonable way to view such restrictions? It is one thing to argue (as Bloomberg presumably would) that the restrictions are justified by the government's supposed duty to minimize morbidity and mortality by preventing people from taking risks (its "highest duty," according to Bloomberg). But it is patently absurd for Bloomberg to claim he is not limiting freedom when he uses force to stop people from doing something that violate no one's rights, whether it's selling donuts fried in trans fat, lighting up in a bar whose owner has chosen to allow smoking on his own property, or ordering a 20-ounce soda in a deli. When, as in this case, his arrogant, healthier-than-thou interference has, by his own admission, zero chance of achieving its stated goal, that fact hardly makes his arbitrary use of government power less objectionable.

More on Bloomberg and "public health" here.