WASHINGTON - Former first ladies Barbara and Laura Bush worked to end illiteracy. Nancy Reagan famously took on teenage drug use. Lady Bird Johnson planted flowers. But none of them has been seared for something as seemingly benign as calling for kids to eat more vegetables, as Michelle Obama has.

Just about everyone will agree that the nation's children are getting fatter and that obesity is a serious health problem. But the first lady's push for healthier meals and more exercise, which marked its first anniversary this month, has provoked a backlash from the right, who complain that the only thing here that's supersized is Big Brother.

Radio talk-show host Rush Limbaugh last week suggested Obama is a hypocrite for dining on ribs and remarked on her waistline in the process.

That was just the latest offering in what has been a steady diet of criticisms.

"Leaders are supposed to be leaders," Limbaugh said. "If we are supposed to eat roots, berries and tree bark, show us how."

Critics have carped about Obama's spread at her Super Bowl party - and have suggested that the child-nutrition legislation she backed in Congress would bring about the end of school bake sales. Her work with the National Restaurant Association to develop healthier menu items has been decried in some circles as a government takeover of business.

And in January, some conservatives suggested that Obama was endangering people, blaming an increase in pedestrian deaths on the first lady's campaign by saying that Americans were putting themselves at risk by walking more.

The criticism is fueled by a rising conservative chorus against the Obamas and comes as Republicans embark on a contest to pick a nominee to challenge the president next year.

Earlier this month, Mitt Romney, addressing the Conservative Political Action Conference in Washington, peppered his remarks with digs at the first lady and her husband.

Ridiculing President Barack Obama's purported move toward the political center, Romney joked that the president's rhetoric had shifted so radically that "he sounded like he was going to dig up the first lady's organic garden to put in a Bob's Big Boy," Romney said.

Later, while equating Obama's economic policies to Marie Antoinette's purported line about the French peasantry - "Let them eat cake" - Romney corrected himself.

"I'm sorry," he crowed. "Organic cake."

Michelle Obama's defenders say her campaign is producing results. "Over this past year, we've seen the first signs of a fundamental shift in how we live and eat," White House chef Sam Kass told a recent meeting of culinary professionals. "We've seen changes at every level of our society - from classrooms to boardrooms to the halls of Congress."

That didn't stop GOP Rep. Michele Bachmann of Minnesota from accusing Obama last week of trying to implement a "nanny state."

Appearing on a conservative radio show, the Republican congresswoman found fault with Obama's latest focus: encouraging mothers to breast-feed their newborn babies. Obama has said children who breast-feed are less likely to become obese.

The first lady's view is "very consistent with where the hard left is coming from," Bachmann said. "For them, government is the answer to every problem."

Bachmann was following the lead of Sarah Palin, who has complained Obama is imparting her worldview on Americans by telling them what to eat.

Myra Gutin, an expert on first ladies and politics at Rider University in New Jersey, said the only other first lady to be as consistently criticized as Obama was Hillary Clinton, for tackling health-care reform in the early years of the Clinton administration.

Clinton, however, "was running a bureaucracy of her own," Gutin said. "It's quite different."

In contrast, Gutin said, Nancy Reagan's "Just Say No" campaign was knocked as a less-than-aggressive response by the White House to mounting drug use.

"Some of the criticism (of Obama), quite frankly, has really shocked me," Gutin said. "There is a certain line with first ladies. You can take a shot, but I don't think people like it a lot. We're not talking about the war; we're not talking about the economy. At some level it begins to sound peevish and almost inappropriate."

Gutin said attacking Obama could backfire.

"While potential first ladies are not a reason for choosing a presidential candidate, this may come home to roost in a year and a half," she said. "Voters may remember it."