Michelle Obama is now a world record holder.

The first lady announced Monday that her October bid to break the record for the most people doing jumping jacks in a 24-hour period succeeded. Mrs. Obama says 300,265 people participated, shattering the old record. The old record was 20,000 people, she notes in a video message on the Let's Move! website.

In order to achieve her goal, Mrs. Obama led 464 elementary and middle-school students from Washington in jumping jacks on the South Lawn of the White House. Other jumping jacks events were held around the world on Oct. 11.

The event was organized by National Geographic Kids magazine, which says this is its fifth Guinness World Record. "The record-breaking effort took place between 3 p.m. (EST) Oct. 11 and 3 p.m. Oct. 12, when anyone, anywhere could participate by doing one minute of jumping jacks.

The event was also a part of the first lady's Let's Move! initiative to promote physical fitness and healthy eating for children.

At the launch of the Let's Move! campaign in February 2010, Michelle Obama said, "The physical and emotional health of an entire generation and the economic health and security of our nation is at stake."

The Let's Move website notes that "Over the past three decades, childhood obesity rates in America have tripled, and today, nearly one in three children in America are overweight or obese. The numbers are even higher in African American and Hispanic communities, where nearly 40 percent of the children are overweight or obese."

IN PICTURES: Michelle Obama's travels with her girls