ABC NEWS' Yunji de Nies Reports:
It was hula hoops and healthy food on the South Lawn of the White House today. The First Lady held a health fair– with cooking demonstrations and exercise stations – all to promote healthy living for parents and kids.
She sampled vegetable and turkey sausage frittatas, vegetable quesadillas, raw fruits, along with apple syrup cinnamon baked apples, exclaiming, "This tastes like apple pie!"
About 60 local elementary school students, teachers and parents were invited to speak with nutritionists and chefs, and get active right alongside the First Lady. Mrs. Obama was not shy, as she hula hooped, kicked off her shoes to jump rope, even running through an obstacle course, smiling and laughing throughout.
Mrs. Obama watched chefs prepare the foods and encouraged children and parents in the crowd to participate. One asked about the President's eating habits, to which the First Lady responded, "He's a very disciplined eater, much more than me. He embarrasses me. I'm eating dessert and he'll say, ‘No, no. I had desert yesterday.' "
Before the fun began, Mrs. Obama addresses the group, striking a more serious tone, emphasizing the need to encourage American children to exercise and eat healthy – both in and out of school.
Because of rising obesity rates, she said, "Medical experts are now warning that for the first time in history of this nation, we're headed for the next generation being on track to have a shorter life span than us."
Mrs. Obama said she relates to working parents who turn to fast food as a cheap, quick solution.
"We're all pulled in a million different directions, working hard, working long hours, trying to do everything, be perfect parents," she said, "When you come home from a long day of work and the refrigerator is empty and you know you don't feel like cooking, the easiest and sometime the cheapest thing to do is to get in the fast food drive through. We've all done it."
The First Lady spoke about her upbringing and how much things have changed from her childhood to that of her daughters'.
"When I was growing up, fast food was a treat. We couldn't afford to get fast food every week," she said, "We didn't have desert every single night. My mother would tell us, dessert is not a right, it's a treat!"
The First Lady continued, "My mother was also very clear in her household that you ate what she fixed," to which the crowd laughed knowingly, "You ate what she fixed, and if you didn't eat that, you didn't eat."
Mrs. Obama was quick to point out that the President and First Tweens do indulge from time to time.
"There's nothing that the First Family loves more than a good burger," she said, " My favorite food in the whole wide world are french fries! I love them, dearly. Deeply. I have a good relationship with French fries and I would eat them every day if I could."
Mrs. Obama explained eating right is not about absolutes but striking a balance. She also spoke about the need for more physical activity in school. "Many kids don't have any access to physical education in the schools. And that's something that's also changed. When I grew up and I went to public schools in my neighborhood, I don't care what you did, you had recess and you had gym."
"One of the things I want to do is to begin focusing on ways this administration can help parents, kids and families in tackling all these challenges," she said, "Not just tell you what to do and what it should look like but help you with some resources so it doesn't feel so impossible."
Mrs. Obama spoke about the Department of Agriculture's Healthier US School Challenge (HUSSC), which recognizes schools that promote good nutrition and physical activity. So far, more than 600 elementary schools are taking part in the program. Mrs. Obama encouraged more schools to join in and offered a personal visit as an added incentive.
"If you're school commits to this challenge, there's a possibility that I'll come check it out. But I'm not coming if you're not a part of the challenge," she said.
Mrs. Obama also said children themselves need to take an active role in keeping themselves healthy.
When it comes to vegetables –"We don't want to hear the whining," she said, "Eat it, just eat."
And she said, turn off the television. At the White House, Malia and Sasha Obama are apparently not allowed to watch TV during the week and are only allowed to do so for a few hours on weekends.
"Because the TVs are off, my girls get up and move. Even if they're pushing each other down, they're running," she said with a smile.
Agriculture Secretary Tom Vilsack joined the First Lady. He praised her for championing HUSSC, ""We could not have a better spokesperson in this country," he said.
The Secretary said that the White House a strong commitment to making healthy foods available to children through the school lunch program. As evidence, he relayed a conversation he had with the President, upon accepting his current job.
"The first instruction I got from my boss," Vilsack said, "'He said, ‘I want our children to be fed more nutritious meals."
Vilsack followed the First Lady through the cooking stations, sampling the various dishes, though he held back when she moved on to the hula hoops and jump ropes.
FLOTUS Fashion Watch: Mrs. Obama wore a teal cardigan over a black and white patterned blouse, topped with a studded black belt and black pants.