New York City’s diminutive dictator of health habits extends his reach:

Suppose you wanted to test the effects of halving the amount of salt in people’s diets. If you were an academic researcher, you’d have to persuade your institutional review board that you had considered the risks and obtained informed consent from the participants.

You might, for instance, take note of a recent clinical trial in which heart patients put on a restricted-sodium diet fared worse than those on a normal diet. In light of new research suggesting that eating salt improves mood and combats depression, you might be alert for psychological effects of the new diet. You might worry that people would react to less-salty food by eating more of it, a trend you could monitor by comparing them with a control group.

But if you are the mayor of New York, no such constraints apply. You can simply announce, as Michael Bloomberg did, that the city is starting a “nationwide initiative” to pressure the food industry and restaurant chains to cut salt intake by half over the next decade. Why bother with consent forms when you can automatically enroll everyone in the experiment?

[...]

When Dr. Frieden and Mr. Bloomberg decided several years ago that trans fats were dangerous, they didn’t simply issue a warning or a set of voluntary guidelines. They insisted on outlawing trans fats in New York’s restaurants.

At the time, it seemed extraordinary for a city to be forbidding its diners to order a legal food product, particularly given the scientific uncertainties about trans fats and the possible harms resulting from the ban.

But that local restaurant policy now seems fairly modest by comparison with Mr. Bloomberg’s and Dr. Frieden’s plans for salt. Soon, wherever you live, wherever you eat, you could be part of their experiment.

In the America of today, there is no aspect of your life that falls outside the domain of government control.