America’s first ladies tend to undertake major social service projects, serving as the figurehead of a campaign for some cause that’s worthwhile, but not politically controversial enough to endanger their husbands. For Michelle Obama.

The cause is childhood obesity. One in five kids today is not just overweight, but obese, experts say; 40 years ago, that proportion was one in 20. The increasing rate produces a series of problems, from straining the health care system to reducing the pool of those eligible to serve in the military.

So Mrs. Obama’s “Let’s Move” campaign hopes to lead the nation to returning to the 1970 child obesity level within 20 years. A White House Task Force on Childhood Obesity on Tuesday released a blueprint for steps to take to reach that goal.

The proposal lists 70 possible steps that could lead to progress, and here’s the surprising part — surprising particularly to those who equate the name Obama with government clout: It includes no federal mandates, no new taxes, no strict regulations on industry. Some such steps could be needed in the future, it said, but first it relies on voluntary steps and public persuasion.

Regulation is “the last thing you want to do,” the Federal Trade Commission chairman said. “You try to start by pushing soft regulation, by using your bully pulpit — by commending the companies that are really stepping up to the plate and sometimes shaming companies that aren’t doing enough.”

Sterner steps might come later, if necessary. A national tax on junk food and sugary soft drinks, new rules on marketing food to kids, subsidies to make fresh fruits and vegetables cheaper? They’re worth study, the report said, but not justified now.The secretary of the Department of Health and Human Services suggested that some state and local governments may want to try out some of these ideas first. For now, Uncle Sam will use the soft approach.