She also tried a little jump rope, The Washington Post reported.
Speaking to dozens of children and parents at a Healthy Kids Fair on the White House South Lawn, Obama noted one in three American children are overweight, a condition known to lead to serious health problems such as high blood pressure, heart disease and cancer in later years.
The situation is so dire, she said, "medical experts are now warning that for the first time in the history of this nation, we're headed for the next generation being on track to have a shorter life span than us."
While sounding that serious warning about the need to eat healthier and exercise more, Obama acknowledged in a light-hearted way how hard it can be to give up unhealthy foods, such has her favorite: french fries. She got laughs when she said: "I love them. Dearly. Deeply.:
"I have a good relationship with french fries and I would eat them every single day if I could. I really would," she said. "But I know that if I'm eating the right things -- and I tell my girls this -- if you're getting the right foods for most of the time, then when it's time to have cake and french fries on those special occasions, then you balance it out."
Obama and Agriculture Secretary Tom Vilsack also pushed his department's challenge to U.S. middle and high schools to serve healthier food and provide more time for exercise and physical activity.
For the first time in more than a quarter century, a new rocket, the Ares 1-X, has been placed on a Kennedy Space Center launch pad in Florida.
NASA said its Ares I-X flight test rocket arrived at the pad atop a giant crawler-transporter at approximately 7:45 a.m. EDT Tuesday. The crawler-transporter left Kennedy's Vehicle Assembly Building at 1:39 a.m., traveling less than 1 mph during the 4.2-mile journey. The rocket was secured on the launch pad at 9:17 a.m.
The rocket is to be launched next Tuesday at 8 a.m. on its first test flight. The Ares I is being designed to carry astronauts into space in the Orion crew exploration vehicle.
During the next week, technicians will perform a variety of electrical and mechanical checks to ready the vehicle for flight. During the test flight, data will be collected from more than 700 sensors throughout the rocket.
"With the arrival of Ares I-X at the pad, this milestone demonstrates NASA's world-class ability to conceptually design, build and process a new launch vehicle in just under four years," said Bob Ess, mission manager for Ares I-X.
Ares I-X is an uncrewed, sub-orbital development test vehicle in a modified Ares I configuration. Ares I-X is the first developmental flight test of the Constellation Program, which includes the Ares I and V rockets, Orion and the Altair lunar lander.
A suicide bomber set off a device in southeastern Iran, killing at least 40 people including several high-ranking Revolutionary Guards officers.
The officials were reportedly meeting with tribal leaders in Sistan-Baluchistan province Sunday when they were attacked.
Iranian leaders at first blamed the United States and the United Kingdom for supporting the bomber -- allegations that were denied -- but Monday said Pakistan was to blame -- an allegation Pakistan denied.
Iran similarly blamed outside forces for violent protests following the disputed election last summer in which President Mahmoud Ahmadinejad was given a second term in office.
There were reports a local group that claims to fight in support of Sunni Muslims carried out the attack.
Six Revolutionary Guards commanders were among the 42 people killed, official Iranian reports said. Dozens of other people were injured. The attack occurred as a meeting between local tribal leaders and the Revolutionary Guards was beginning.