Her daughters were 6 and 9, and Michelle Obama was like any other working mom – struggling to juggle office hours, school pick-ups and mealtimes. By the end of the day, she was often too tired to make dinner, so she did what was easy: She ordered takeout or went to the drive-through.

She thought the girls were eating reasonably well – until her pediatrician in Chicago told her he didn’t like the weight fluctuations he was seeing.

“I was shocked because my kids looked perfectly fine to me,” Obama says. “But I had a wake-up call.” Like many parents, however, “I didn’t know what to do.”

Today, the self-described “mom in chief” is launching Let’s Move, a campaign to help other parents deal with a national health crisis she describes in epic terms.

The goal: to eliminate childhood obesity in a generation.

“It’s an ambitious goal, but we don’t have time to wait,” the first lady said in an interview with USA TODAY in her spacious office in the East Wing of the White House. “We’ve got to stop citing statistics and wringing our hands and feeling guilty, and get going on this issue.”

She says she intends to “sound the alarm” about the epidemic: About 32% of children and adolescents today – 25 million kids – are obese or overweight, according to the Centers for Disease Control and Prevention.

Those extra pounds put kids at a greater risk of developing a host of debilitating and costly diseases, including type 2 diabetes, high blood pressure and high cholesterol.

A 2005 study found that kids today may lead shorter lives by two to five years than their parents because of obesity. Meanwhile, the costs “take your breath away,” Obama says.

Obesity costs the country a staggering $147 billion a year in weight-related medical bills, according to government data.

Obama says she will use all the power of her White House pulpit to promote a multifaceted campaign that will include more healthful food in schools, more accurate food labeling, better grocery stores in communities that don’t have them, public service announcements and efforts to get children to be more active. Some of her plans, such as tax incentives for businesses, will need congressional approval.