Yes, exhausted, hungry parents: The Obamas have been there, too.

"We were fortunate enough to have a pediatrician who kind of waved the flag and said, 'You may want to keep an eye on your children's BMI,' because one was getting a little out of kilter."

She's referring to body mass index, a correlation of weight and height that can be one of the first signals that a diet is slipping. "He was a pediatrician who practiced medicine in a predominantly African-American urban community and was seeing trends in obesity," she says.

Naturally, she was looking at her kids the way most of us do: seeing nothing but their beauty. "I hadn't even noticed," Mrs. Obama says. "She was cute. Just a little brown kid; seemed fine. But I made some very minor changes. We eliminated processed food. We took sugary drinks out. We tried to have [family] dinner more. We put more vegetables and fruits into our diet. It was very minor stuff." (Always protective of her children's privacy, Mrs. Obama didn't specify which daughter had the weight problem.)

Do you hear her point? "Very minor stuff," she says. But how many of us act on that knowledge, as the Obamas did? When you look at the long list of diet books published every year and listen to the debate over healthcare reform, you get the impression that it's strictly the province of professors and political operatives. In fact, it's as simple as a mom putting a carrot in her kid's hand rather than a candy bar. Don't think you can do that? Maybe you just don't realize how powerful you are as a parent.

The American Dietetic Association says 40 percent of kids cite their parents as their top role model. Seventy percent say they turn to their parents for information on nutrition and healthy eating. If you can set a good example, you have a fighting chance of countering the $1.6 billion a year the food industry spends to sell a chubby lifestyle to your kids. (So far, the marketers are winning. The USDA estimates that the average 6- to 11-year-old consumes around 1,985 calories a day, even though the average young couch potato needs just 1,250 to 1,680.)

"A lot of parents tell me, 'My kids don't like healthy foods,'" says David Katz, M. D., an associate professor adjunct of public health practice at the Yale School of Public Health. "Well, 'finicky' is not an excuse. You never hear a parent say, 'My child doesn't like to look both ways before he crosses the street.' They tell him to do it. They should do the same thing with dangerous foods. More of today's kids will die of complications from bad foods than from tobacco, drugs, and alcohol."

The "minor stuff" worked: "We saw some really significant changes," Mrs. Obama says, "to the point that the next time we saw the doctor, he said, 'What on earth are you doing? I said, 'Not that much.' You know, [the girls] were always active; it was really minor changes in the diet--minor--and educating our kids as well, so they read labels and took stuff out and refused to go to certain places to eat. The more they learned, the more they embraced. Things turned around--and we found, Barack and I, that our own health patterns were better."

Fertilized by such realizations, gardens sprout.

"If, with these minor changes and this little bit of information, we could make changes outside of the White House, man, what could we do if we were in the White House?" Mrs. Obama asks, thinking back. "[If] I could share these experiences and help other families struggling with some of the same things? The garden was an important step to that--you know, stepping back to the victory gardens of Eleanor Roosevelt and thinking about how powerful that could be."

History resonates in The White House.

Even the upholstery exhales past lives and grand achievements. So it was interesting to hear how present the First Lady's own past is when she considers her family's path. She vividly remembers a time when her birth family made healthy choices not because they were pioneering nutrition nuts but out of economic necessity.

"Our lifestyle back then was very different in how families, particularly working-class families, lived," she recalls. "There was a limit to our resources. We didn't have snacks and juice boxes. If we were at camp, lunch was a leftover sandwich with a piece of fruit. Dinner was more: You sat around the table and had a conversation, and it wasn't about eating everything. Those values, even though they were the result of economic circumstances, were still really good traditions, and they created some healthy boundaries about food."

Compare that to today. We shop in grocery stores laden with options--47 salad dressings alone--yet they're reminiscent of the Bruce Springsteen song "57 Channels (And Nothin' On)." As the manufactured-food smorgasbord spreads along with our collective waistline, it's as if our choices are getting worse, not better.

The current "locavore" movement, at its base, reflects a yearning for a time when food options were simpler and healthier. Locavores are rebelling against modern ingredients lists, which could easily be preceded by the words "Fashioned from the food laboratories of Dr. Strangelove." One of the primary effects of those chemical machinations is to fool your hypothalamus, according to Yale's Katz.

Here's how it works: The area at the base of your brain contains hunger regulators for the principal flavors that make up a diet: sweet, salty, and bitter. Long ago, it led Homo sapiens to sample different foods; when you filled up on one taste, you stopped eating and sought another, thereby ensuring a variety of nutrients. Now the food companies and their scientists combine sweet and salty flavors within single foods--for example, a cup of cornflakes has more salt than the same amount of cheese curls, but the salt is masked by sugar. As a result, you keep eating, because you never exhaust your taste in any single area. "Every processed food has chemical flavor enhancers to keep you eating," Katz says.

The First Lady harks back to an era when nobody needed to talk about the hypothalamus, because Big Food hadn't yet learned how to manipulate it. But she also takes the long view with her girls. "I tell them, 'Teaching you about how to eat really isn't about right now,'" she says. "'I'm your mom; I can make you eat what I think you should eat. But think about when you're on your own. When you get to college, you can eat pizza every single night. I did. But that's not healthy. When you grow up and have families, you've got to know how to eat so you can teach your kids.'"

It's something of a relief to hear her admission: I did it. Will we be smart enough to realize our mistakes, as she has, and change our ways?

Mrs. Obama doubles back to my question about their being the "first family of health and fitness." "I see our lifestyle as a way to educate our kids about how to live their lives. And we've tried to do that for every kid around the country. If that makes us the health-and-fitness first family, so be it. I try to make sure that families don't try to attain something that's not possible."

She's referring to the people who ask her "How do you do it?" Her retort: In the White House? With a kitchen staff, a beekeeper, and a guy the president refers to as the "crust master"? It's pretty easy. But the Obamas have been a working couple with kids longer than they've been Commander-in-Chief and First Lady.

"I know how hard it was to get to the gym and to cook balanced meals when you were coming in from work, getting to the grocery store every couple of weeks," she says, speaking of their early careers as a hospital administrator (Michelle) and state legislator-cum-law-school professor (Barack). She knows from picky eaters who can't ring the White House kitchen for some fresh blueberries.

"Kids don't eat rotting fruit," she notes. "If there's a bad grape, then they're all bad. It's like, 'Ooh, it's a fruit fly! I'm not eating those strawberries!' Modern life doesn't make it easy for families to eat healthy, and I don't want people to feel like if they can't do what Michelle Obama did then somehow they're inadequate. There's enough of that guilt going around for parents across this country. We don't want to add to that."

During our talk, I floated a theory of mine to the First Lady: Families, I posited, are the No. 1 healthcare organization in the country. Mrs. Obama was ready to entertain the idea. "Family is key," she said. "And you've got to have strong families with good information and the ability to access the resources they need to take care of their families. But the institutions that affect the lives of families and communities also have to take on their role in the solution. It's got to be all of us working together for the sake of our children's health."

Michelle Obama is the head of the first family, yes. But it's clear she believes it's first among equals. We're all in this together, after all. Marian Robinson is delivering a larger lesson there as well: If you're close enough to smell an extra Oreo cookie on your kid's breath, that means your kid is close enough to benefit from the example you set. Do and say the right things and maybe your kids will even think you're omniscient.