NEWARK, N.J. - A group of Newark schoolchildren received a pep talk on healthy eating and exercise Thursday from Michelle Obama, who assured them that she was putting her own advice into practice at the White House.

"We've sworn off the elevator at our home," she said. "We walk up the stairs. The kids don't like it, but they do it."

Obama visited the Maple Avenue School to talk to students about how eating better and exercising more could improve their lives. The event was part of her "Let's Move" initiative against childhood obesity. She met with some students individually and then addressed a school assembly.

Childhood obesity rates have tripled over the last three decades, and obesity-related health-care costs are about $147 billion a year, according to the White House.

"Let's Move" seeks to attack the problem by educating children and parents about healthy eating choices through advertising, food labeling, and healthier food in schools.

Maple Avenue students have started several programs, including exercise and dance classes, partnerships with local farmers' markets to give parents and children more healthy options, and rewards for students who make informed nutritional choices.

Some habits will always be hard to break, however.

"I know some kids who eat at McDonald's almost every day," seventh grader Evan Thomas said Thursday. "I don't go that much anymore."

Obama entered the auditorium to a chorus of screams from the third through eighth graders. After her speech, she exchanged hugs and handshakes with many of them as a sound system blared Aretha Franklin's "Respect" and the Jackson Five's "I Want You Back."

Newark Mayor Cory Booker, a national cochair of "Let's Move," called Obama "a chief provocateur in one of the most critical issues facing our nation."

Obama praised Booker's efforts in Newark and told students that they could start small and still make a difference.

"You can do it just by setting an example," she said. "You don't have to change the whole world at once. You can change the person who sits next to you in class."

"It's amazing," said Sihomara Ramos, 10. "It's a small school without that many people, so it makes us feel important. It makes us feel we actually mean something to her."