Shortly after President Obama was elected to the White House in 2008, first lady Michelle Obama divulged some sensitive, personal details: The Obama children, Malia and Sasha, were gaining weight.

In interviews and speeches, she described her worry about her family's health and a pediatrician's warning that her daughters' body mass index (BMI) was creeping up.

"Even though I wasn't exactly sure at that time what I was supposed to do with this information about my children's BMI," the first lady said in 2010, "I knew that I had to do something. I had to lead our family to a different way."

That personal struggle became political. Obama has spent the bulk of her time in the White House doing something unprecedented for a "mom-in-chief": pushing hard against childhood obesity. Today, her Let's Move campaign is her highest-profile endeavor, far better known than her Joining Forces campaign to support service members and their families, or Let Girls Learn to advocate for girls' education around the world.

But I have to admit something: I was skeptical of the influence Obama could have on the nation's health.

We know obesity is disproportionately caused by overeating rather than a lack of exercise. And the first lady's initial championing of physical activity — her pushup competitions with Ellen DeGeneres, the dance-offs with Big Bird — seemed like a charming cop-out. She's also partnered with the very food giants that are synonymous with the problem, such as soda makers. Isn't that like teaming up with cigarette companies to get kids to stop smoking?

The government has also often exacerbated the problem over the years, in the form of subsidies for pizza- and french fry–filled school lunches, and generally allowing the industry, and not the best available science, to guide nutrition policy.

I wasn't confident that FLOTUS, with no legislative power, could make a dent.

Then I spoke with a dozen people who worked closely on her campaign, as well as the health and food policy researchers who studied it. (Despite repeated requests, Obama's office did not grant an interview with the First Lady on childhood obesity — and she has demurred from discussing the details of this work with other members of the press as well.)

I learned that some of the very things that made Michelle Obama sometimes appear soft — the industry collaborations, the emphasis on exercise — were part of the shrewd strategy that made her effective. Through her leadership, the Obama administration seized on a moment when America started paying attention to food, and made fighting obesity a top priority — both symbolically and legislatively.

Obama planted a garden, waged snappy social media campaigns, and worked behind the scenes with researchers, lawmakers, heads of government departments, schools, and food giants to quietly change what Americans eat.

Even observers who previously worried about Obama's food industry partnerships now called her advocacy "brilliant," "unprecedented," and a "godsend."

"All that attention to the issue has really helped push the discussion forward," said Kelly Brownell, a Duke University obesity researcher — and former critic.

Observers said this administration — largely because of the first lady's focus — will have more of an impact on obesity in this country than any other in recent history. (Obama is also the first modern FLOTUS to have a major influence on policy initiatives.)

Marion Nestle, the longtime food policy researcher who was also previously skeptical of the first lady's approach, is now among the impressed. "This was the first time in my life someone in the White House was interested in the same kinds of issues I'm interested in," she recently told me. "We're going to look back in 10, 20 years and wish she were still around."

Through the force of her leadership, FLOTUS improved school lunches

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Michelle Obama eating lunch with kids in Alexandria, Virginia, January 25, 2012.

There's near universal agreement among obesity researchers that the fight against obesity is all but lost once people seek help from their doctor to manage their weight.

Diets and medications work for some people whose health is compromised by their weight, but they fail most. Bariatric surgeries offer hope, but they come with real risks. So experts say fighting obesity really means preventing it, long before a person becomes a patient.

Say, in schools.

As recently as 2010, researchers found that schools were commonly serving children the kinds of calorie-dense and nutrient-poor meals — pizza, hot dogs, chicken nuggets, french fries — that increase kids' risk of obesity instead of helping them avoid weight gain.

Many low-income families rely on schools to feed their children at least one meal a day. (School lunches, and even breakfasts, are free for families with incomes that fall a certain percentage below the poverty line.) So offering kids nutritionally bankrupt meals, and driving up their risk of chronic diseases, isn't just a nutrition problem; it's a social justice issue, too.

Through consultation with some of the nation's top obesity experts, Michelle Obama zeroed in on solving the school lunch problem. And that's where the Healthy, Hunger-Free Kids Act of 2010 came in: legislation centered on cleaning up school food. Getting the act passed — and keeping it in place — became a key focus of the Let's Move campaign.

The law required the federal government to use recommendations from the Institute of Medicine to make the National School Lunch Program more nutritious, with more whole grains, a wider variety of fruits and vegetables, and less sodium and meat.

The law also mandated that schools stop marketing the fat-, sugar-, and salt-laden snacks — the sugary beverages, the chocolate bars — in cafeterias and vending machines, and that they replace those offerings with lower-calorie and more nutritious alternatives like fruit cups and granola bars. Finally, it made it possible for schools that have high poverty rates among students to provide free breakfasts in addition to lunches, without requiring paperwork on whether individual students meet certain poverty criteria.

But the act didn't pass easily. GOP leaders said it was emblematic of the nanny state. The School Nutrition Association — which receives funding from the food industry — argued that it would cost schools a lot of money to implement, and that kids threw out some of the fruits and vegetables the schools were required to put on their lunch trays.

This fight continues today. "Every time there's an appropriation bill, there's been an aggressive attempt to roll back the reforms we made," said Sam Kass, the former White House assistant chef whom Michelle Obama hired to be a nutrition policy adviser and executive director of Let's Move.

So how did Michelle Obama manage such a contentious change?

First, she got her husband on board with the Let's Move campaign, and he made childhood obesity and pushing for legislation like the Healthy, Hunger-Free Kids Act a priority for the administration. "The reason the president was pushing [the bill] was this was [Michelle Obama's] priority," Kass said. "So all credit goes to her on that. But the president runs the administration, so if he says, 'This is our priority,' it's everyone's job to get it done."

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New salad bars at the Montrose County school district in Colorado.

As Politico explained it, "The day the Let's Move! campaign launched, the president put out an executive order creating the first-ever national task force on childhood obesity, which would be led by his Domestic Policy Council and work in tandem with the first lady's campaign." About a dozen federal agencies started to work on the report's 70-plus recommendations.

That included the USDA, which administers the school lunch program.

"She had all the levers of the Obama administration at her disposal, from the White House Policy Council through to all the agencies," said Sean McBride, a consultant to the food industry in Washington who previously worked with the Grocery Manufacturers Association.

Of course, the bill went through in an era when there was already a growing awareness that Americans needed to "eat food, not too much, mostly plants," as author Michael Pollan put it. Many in the health community were already talking about cleaning up the food in schools.

But while food advocates had been working on these issues for years, they say they couldn't overcome the political hurdles until the Obama White House.

"When we were pushing through [the act]," said Margo Wootan, a longtime nutrition advocate and director of nutrition policy at the Center for Science in the Public Interest who was involved with the bill, "that was the first time I actually worked closely with White House legislative staff — not only in the East Wing but in the West Wing as well."

There were also frequent sit-downs with the USDA, schools, industry representatives, and lawmakers — talking through the content of the regulations and plotting how to fend off opposition. Obama herself, Wootan said, helped "smooth things over with some members of Congress [who opposed the bill]."

As Kass said, "The bill would not have passed without both the first lady and the president personally getting involved and making that bill pass." (Kass also helped the First Lady build the iconic White House Kitchen Garden in 2009 — the first at the residence since Eleanor Roosevelt's Victory garden.)

Healthy, Hunger-Free Kids is now widely considered a landmark piece of legislation and a boon for public health. As Juliana Cohen, a nutrition professor at the Harvard School of Public Health, points out, the National School Lunch Program feeds more than 30 million children every day — and the majority come from poor families who rely on these meals for up to half their daily energy intake.

It will take years to know how much this legislation moves the needle on childhood obesity. But early measures suggest promise. According to the USDA, as of December 2015, 97 percent of US schools are now meeting the new standard. Researchers who have studied the impact of the law have been finding that kids across the country are now eating more produce and whole grains.

Obama helped clean up the $350 billion market of packaged foods

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First lady Michelle Obama unveiling the new nutrition facts labels.

In addition to her leadership and behind-the-scenes maneuvering, the first lady managed to influence food policy by maintaining a positive public image. That involved assembling a staff around her who could carry out Let's Move's ambitions on her behalf.

As the symbolic figure head and leader of the campaign, "Obama stayed above the fray," McBride said, leaving her staff, along with the Domestic Policy Council, to transmit Let's Move's goals to the federal agencies. "The leaders of those agencies took over and carried the ball," he added.

Among the most prominent of her staff members was Kass. "Sam was the tactical leader, the manifestation of the first lady's food policy goals, and generally those goals were set by the White House," said McBride. In Kass's own words, "My role was negotiating in the policy nitty-gritty and with the companies. Her role was to set the vision."

Part of that vision included bringing more transparency to what's in our packaged food. At Obama's urging, the agency enacted one of the most dramatic overhauls to nutrition labels in decades. And last May, Obama was the one who announced the final version of new food labels, which is slated to appear on everything from sodas to candy bars, yogurts, and cereal packages starting in 2018.

The labels will finally give consumers long-sought-after information about added sugars in foods — data that health advocates had pressed the food and beverage industry to provide for decades. They'll also list nutrition information about serving sizes in portions that more accurately reflect how much people eat.

More subtly, the new labels are expected to get companies to reformulate products to make them healthier and less sugary.

Another milestone came in June 2015, when the FDA banned trans fats from the food supply within three years. The policy brought the US in line with other countries that have already banned the harmful fat, including Denmark, Austria, Iceland, and Switzerland. And it came long after scientific evidence had mounted for years that these processed unsaturated fats increase the risk for heart attacks and strokes.

"The FDA made nutrition a priority [under Obama's leadership]," Wootan summed up.

Before the trans fat ban turned into a federal policy, Michelle Obama, along with Sam Kass, had already been working with companies, like Walmart, to get them to pledge to remove trans fats (along with reducing sodium and sugar) from products sold in their stores and to bring affordable, nutritious foods to food deserts by opening new stores.

Part of that collaboration with companies came through the Partnership for a Healthier America, which launched in conjunction with (but independent from) the Let's Move campaign. In effect, the group is the outreach arm of Let's Move and its partners include industry groups, as well as nonprofits and research institutions.

Among the partnership's wins has been getting food companies — such as PepsiCo, Coca-Cola, and General Mills — to commit to cutting calories from the food supply. At the latest count in April, it had already removed 6.4 trillion calories (or 78 calories per person) by reformulating products and shrinking serving sizes.

Lawrence Soler, PHA president and CEO, says these gains have come as a result of a positive feedback loop that starts with Michelle Obama.

"People have responded to her message and to her as a messenger in a very real way," Soler said. "The fact that consumers are looking at food and physical activity in a new way has transformed where industry is going. And the Industry is responding to this enhanced consumer interest in changed products, healthier alternatives, and more of a focus on health."

The shrewd choice of promoting water instead of attacking Big Soda

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First lady Michelle Obama unveils the Drink Up logo to encourage water consumption on the South Lawn of the White House in 2014.

Even with all her charisma and determination, the first lady's close work with the food industry has also attracted criticism over the years. "If you look at the food industry players Let's Move has been engaged with, they are some of the same players that are manufacturing products that contribute a lot of calories to the American diet," Brownell said.

These companies need to maintain their market share while being perceived to be helpful and instructive, he added. "So critics would say the industry is using this as cover — a show of good faith — trying to make changes when they are really not doing so much."

Early in her obesity work, Obama called on food companies to stop marketing junk food to children. But in 2011, the administration tried (and failed) to pass voluntary guidelines that would have curtailed the food industry's ability to peddle to kids.

"The industry opposed it more vigorously than anything I've worked on in 20 years," said Wootan, "even though it was voluntary. And the administration at first pushed back then gave into the industry lobbying effort."

(Kass says there was nothing more the administration could do since the guidelines fall under the Federal Trade Commission, which the White House does not control.)

According to a Reuters investigation, the food industry responded to Obama's focus on obesity by doubling spending on lobbying between 2010 and 2012 alone.

"[Marketing to children] is a topic where collaborating with industry isn't going to work," Brownell said. "Food companies desperately want to maintain their ability to market foods to children."

On the flip side, he added, working with the food industry may have been a wise choice as another avenue through which Obama could change how we eat. "If [food companies] make changes," Brownell said, "that could affect a lot of people all at the same time."

William Dietz, a longtime obesity researcher who helped identify the obesity epidemic in the US while at the Centers for Disease Control and Prevention, said Obama was particularly savvy in her industry collaboration. There's plenty of scientific evidence that sugary drinks contribute to obesity, tooth decay, and diabetes, but Obama chose to promote water instead of warning parents and kids against the sweet stuff.

"She hasn't directly attacked sugar," Dietz added. "I think what's made her effective is that's she's focused on a number of public health initiatives without demonizing any particular product."

 Paul J. Richards/AFP/Getty Images
Former White House chef Sam Kass, pictured here with the first lady and schoolchildren, did a lot more than plant the White House garden.

Looking back, Kass said, he sees this approach as part of Michelle Obama's core philosophy. She wanted to both "create a space that anybody who was serious about becoming a part of the solution had a seat at the table" and move past the gridlock and finger-pointing that characterized many public health food fights.

This set Obama's team apart from other obesity advocates, said Susan Neely, president and CEO of the American Beverage Association.

"They decided that rather than lambasting industry or criticizing industry, they should invite companies or the private sector to participate, and I think they made it clear the bar was going to be high in terms of what legitimate participation would look like," she noted.

Then there was the smart choice of a name. Marion Nestle noted that she used to be concerned that the slogan placed too much of an emphasis on physical activity and was too soft on the food industry.

But "Let's Move" can be interpreted different ways, and now Nestle sees it as an important political calculation. "It's very hard to say [Obama] would have been better off taking on the food industry in a more direct way. She had no power to do that — no legislative power — and nothing but leadership to go on," she says.

That didn't mean she was soft on the industry, however. As Obama put it in a 2010 speech to the Grocery Manufacturers Association, kids are unhealthy, eating too much sugar and too many snacks, and those changes have come largely because of the industry. (The Grocery Manufacturers Association declined to comment for this story.)

Nestle called that early speech "extraordinary" and still wonders if the first lady knew the fierce lobbying and "near impossible circumstances" she'd be up against as she tried to steer America's eating habits in a healthier direction.

Kass views the speech as Obama's message to the industry that "the status quo is unacceptable, families are suffering, and in areas where the food industry was undermining public health, we are going to fight like hell to the end."

The next White House administration should build on Obama's legacy

Even those who are now leveling heaps of praise on the first lady acknowledge that preventing obesity will require much more fundamental shifts.

American diets on average still fall dramatically short of the minimum nutrition standards, particularly for fruit and vegetable consumption. And researchers have pointed out that if Americans actually followed the US dietary guidelines and started to eat the volume and variety of fruits and vegetables health officials recommend, we wouldn't have nearly enough to meet consumer demand.

 Javier Zarracina/Vox

Nutritious foods like fruits and vegetables are still more costly than fats, grains, and sugars, and we're bombarded with messages to eat more junk foods and snacks. As recently as 2014, food companies spent $1.28 billion on snack food advertising — and the bulk of that went to the salty and sugary options.

The result is that while rates of childhood obesity have leveled off by some measures, they haven't reversed. And adults are becoming more obese.

"In a perfect world, you'd try to address some of the big issues, such as marketing of food to kids and the relative costs of healthy and unhealthy foods," Brownell said.

 Javier Zarracina/Vox

Governments could do this through taxes on junk foods, bans on junk food marketing to children, and efforts to shift which crops are the subject of federal research funding and subsides away from corn and wheat — which go into processed foods — and toward fresh produce.

Tackling America's obesity problem needs to involve more than making junk foods more healthy; it needs to make healthy food more visible and available, said Michael Moss, author of the book Salt Sugar Fat.

"As much as I've harped on the companies about salt, sugar, fat, reducing the salt, sugar, fat in their products — as they are now all doing — is probably not the priority for a healthier diet," Moss said. "Adding good stuff is much harder than shrinking the bad."

Looking back, Kass hopes people appreciate how challenging improving the food environment is. "What people don't understand is just how hard change really is, how hard every right and every victory comes — particularly in this day and age, with Congress deadlocked and cynicism at all-time highs."

Overcoming that cynicism — while also building on Michelle Obama's legacy — is the challenge the next administration inherits.