(CNN) -- First lady Michelle Obama's drive to stop a Republican-led effort to slow adoption of nutrition standards for school meals, a centerpiece of her anti-obesity "Let's Move" campaign, was dealt a setback in Congress.
Democrats aligned with Mrs. Obama on the issue failed on Thursday to strip the proposal from a $142.5 billion Agriculture Department spending bill, which was approved by the Appropriations Committee and sent to the full House for consideration.
The controversial plan offered by Rep. Robert Aderholt of Alabama would give schools struggling financially an extra year to comply with rules approved by Congress in 2010 to limit fat and salt and promote fruits, vegetables and whole grains.
"I want to be clear that everybody supports healthy lunches and meals for children, but the bottom line is the schools are finding the regulations to be too much too quick," Aderholt said during consideration of the measure by the appropriations panel. "School districts need more time to implement the changes."
An amendment proposed by Democratic Rep. Sam Farr of California to strip Aderholt's language from the bill failed 29-22 on a party line vote.
"It gives schools an opt-out saying you don't have to participate in the school lunch program cause it's hard. Well, we don't tell kids, 'Look you don't have to take math if it's hard or science if it's hard. You don't have do P.E. if it's hard,'" Farr said.
"This opt out for nutrition is just the wrong way to go particularly at this moment in American history when we're really trying to figure out how we can raise a healthier society," Farr said.
Mrs. Obama's strong pushback on a legislative issue marks a rare political foray.
She has promoted healthy eating and exercise through her White House garden and her "Let's Move" campaign for years, but she has never previously inserted herself so deeply into a congressional debate.
She has taken a public stance on the bill and urged Democrats, health advocates and ordinary people to fight the waiver and other proposed changes to nutrition programs.
"Remember a few years ago when Congress declared that the sauce on a slice of pizza should count as a vegetable in school lunches?" she wrote in an opinion piece published in the New York Times on Thursday.
"You don't have to be a nutritionist to know that this doesn't make much sense. Yet, we're seeing the same thing happening again with these new efforts to lower nutrition standards in our schools. Our children deserve so much better than this," she said.
Mrs. Obama hosted a roundtable on school meals on Tuesday and an off-the-record conference call with advocates last week, and her office says she is not backing down on this issue.
Farr hopes the waiver language can ultimately be defeated in the full House.
Similar legislation in the Senate does not include the waiver language. If it survives a House vote and the Senate approves its version of agriculture spending without it, then the two chambers would have to resolve the issue through negotiation.