Former first lady Michelle Obama made her first high-profile public appearance on Friday since leaving the White House in January.
Mrs Obama, who championed healthy eating and physical activity among children as first lady, was the keynote speaker at the Partnership for a Healthier America summit in Washington.
"We got to make sure we don't let anybody take us back. Because the question is 'where are we going back to?' What is it that people, and this is where you really have to look at motives," Obama said.
"You have to stop and think 'why don't you want our kids to have good food at school?' What is wrong with you? And why is that a partisan issue? Why would that be political? What is going on?" she said to applause.
Mrs Obama's appearance comes as a much-delayed U.S. rule requiring restaurants and retailers to clearly display food calorie counts is pushed back again, and could be rewritten or scrapped as the Trump administration rebuffs Obama-era regulations.
Notice came shortly after the U.S. Department of Agriculture relaxed some school lunch rules that were part of the former first lady's signature effort to fight childhood obesity.
It was not clear if Mrs Obama was speaking specifically about the new rules or more generally about the direction of healthcare in America.
The former first lady also said that life outside of the White House has been good.
"Being 'former' is all right. I'm good with it," she told the moderator who had asked how things have been for her and since the end of Barack Obama's 8-year-long presidency.
"President's good. You know, running around out there in the world with his shirt unbuttoned," Mrs Obama joked, in reference a speech given by the former president earlier in the week in Italy during which he was tie-less and kept his shirt unbuttoned at the top.
'What is wrong with you?' Michelle Obama asked the Trump govt after it relaxed her school lunch rules||The former first lady had championed healthy eating and physical activity among children||Her regulations had cut sodium and increased whole grains served in school meals