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.
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.
China marked the 60th anniversary of the assumption of power by the Communist Party with a huge parade that show cased its military might.
The ceremonies centered on Tiananmen Square where, on Oct. 1, 1949, Mao Zedong declared the establishment of the People's Republic of China.
The parade with an estimated 100,000 participants showed off military hardware and serves as a reminder the world's most populous country -- 1.3 billion -- can field an important army in the traditional sense of military power.
But China's true strength wasn't seen on the parade grounds. Instead, it is inked in ledger books where the figures show Beijing holds considerable international sway economically. The United States is particularly vulnerable along this line as China in recent years has amassed more than $1 trillion in U.S. dollars in its foreign reserves (and another $1 trillion in other currencies).
It was the third series of missile tests by Tehran, which had a secret nuclear facility unveiled last week and has talks with the permanent members of the U.N. Security Council and Germany this week about its nuclear program.
Iran says its nuclear program is for peaceful purposes but many Western countries fear it may be a precursor to Tehran developing a nuclear weapon.
The Iranian leadership, particularly President Mahmoud Ahmadinejad, has been openly hostile to Israel.
Tests over the past few days included Monday's firing of the Shahab-3 rocket, which is believed to have a range of 1,240 miles. Two classes of missiles with less range were fired Sunday.
Even before the Monday tests, U.S. officials said they had the international support to impose "severe additional sanctions" on Tehran. However, Security Council members Russia and China have been successful in the past in keeping tough penalties from being levied. It is unknown if the revelation of a secret nuclear facility would change that stance.