Today, first lady Michelle Obama launched her “Let’s Move” campaign, aimed at eradicating childhood obesity. Before the she made her announcement, attendees heard speeches from the president of the American Academy of Pediatrics, an urban farmer, two mayors, and a student.

The urban farmer seemed out of place, because he made little effort to connect his locavore ideology to the problem of childhood weight gain. Of course, children will be healthier if they eat lots of fruits and vegetables, but there’s no reason those fruits and vegetables have to be grown in their cities instead of, say, shipped in from a field in California. The farmer railed against buying food from foreign countries — which, again, is no reason to avoid food from California, even if you accept his protectionist premise. Then he concluded with a few more off-topic pronouncements, including, “When farmers are in business, schools are out,” which sounds to me like an argument against relying on local food for children’s nutrition, and a recommendation that cities grow food in vacant buildings. (Not vacant lots, vacant buildings.)

The mayor of Hernando, Miss., offered more relevant comments, although he too gave the obligatory nods to farmers’ markets and urban gardens. He had a lot of ideas about things cities can do to invite physical activity, such as repairing sidewalks and building playgrounds. The mayor’s emphasis on local policies rather than federal mandates was refreshing. (You see, I have local biases of my own.) And I appreciated it when he said that government should not tell people to be healthy because “that’s a private decision.”

The mayor of Somerville, Mass., advocated a more invasive approach for government. His “Shape Up” campaign goes so far as to place a public stamp of approval on certain menu items at restaurants. Even more troubling is the mayor’s declaration, “The healthy choice must be the easy choice.” This recalls the attitude expressed by a student in Clayton when she spoke in support of the proposed smoking ban: If a choice is good, the city should ensure that it is also easy and fun. In other words, you shouldn’t have to make any sacrifices or be at all inconvenienced when you do the right thing — not if the government can help it. Take that way of thinking just a tiny step further, and the government will be making your choices for you.

While most of the speakers had creative plans for cities and schools, none of them explained why the federal government should play a role or why change couldn’t come from the ground up. The first lady emphasized that her campaign won’t try to impose Washington’s vision on everyone, but it’s hard to believe that when she says she’d like to turn convenience stores into produce markets.