A promotional portrait of the Depression-era “Little Rascals” shows a Hollywood ideal at a time when parents’ biggest worry about children’s weight was undernourishment. (MGM Studios/Getty Images)

In 1972, a Las Vegas businessman named Len Frederick introduced a new kind of lunch to cash-strapped schools eager to see their cafeterias turn a profit. Instead of chicken or meatloaf, carrots and a carton of milk, students could eat hamburgers, hot dogs and French fries, and drink milkshakes or soda. All Frederick had to do to square his “combo meals” with national nutrition standards was fortify them with vitamins and add a sprinkle of wheat germ to the buns. Pickles counted as a required vegetable. ¶ As historian Susan Levine recounts in her 2008 book “School Lunch Politics,” Las Vegas students lined up eagerly for the new fast-food-style menu, and the schools made money. But in 1978, a food critic found that given the freedom to pick and choose, most children weren’t getting the technically nutritious combo — they ended up with a lunch more like “two cinnamon buns and a Coke . . . four sugar cookies and a Sprite, or two bags of French fries and a milk shake.”

In hindsight, it’s easy to see the Las Vegas innovation as a harbinger of today’s fast-food-saturated environment and the nation’s childhood obesity problem — now so severe that some doctors predict that today’s kids will be the first in two centuries to have a lower life expectancy than their parents.

But back then, American policymakers were more concerned about undernourishing children than with overfeeding them. “Historically, the concern had always been lack of availability of food,” said historian Peter Stearns of George Mason University, “and work activities that were physically demanding.” As Levine notes, right up until the 1980sgovernment standards set minimums on calories, protein and vitamins in school lunches. But they put no upper limits on calories or fat or sugar or salt.

The widespread alarm about childhood obesity is a relatively recent phenomenon, historians agree. But what’s not new is that political and economic interests time and again have trumped science and health concerns in shaping what we feed our kids and, consequently, in shaping our kids’ bodies.

Fear of malnutrition

In 1933, Labor Secretary Frances Perkins told the country that one-fifth of all preschool and school-age children were “showing signs of poor nutrition” — practically a mirror image of today’s warnings that more than 18 percent of children in the United States are obese. Parents had been fretting over undernourishing their children from the start of the century, said Harvey Levenstein, author of “Paradox of Plenty: A Social History of Eating in America.” “People used to think if your child was chubby it meant they were healthy,” he said.

Although U.S. children’s health improved through the first half of the century — even during the Great Depression — fear of malnutrition persisted. It was reinforced, Levine said, by reports that “some huge proportion of the young recruits were rejected for service” during World War I because they were too skinny, too weak or otherwise too poorly fed. Scientists began calling attention to vitamins in the 1940s, adding the worry that even those who got enough food could suffer deficiencies in invisible but essential elements.

When the United States entered World War II, the idea spread that with so many women in the workforce, schools needed to take more responsibility for childhood nutrition. Leaders in the new science called home economics worked out the required calories and nutrients for military rations and school lunches.

The first national school lunch program began in 1946, and its chief purpose was to get enough nutrients into American kids. The meals “contained high levels of fat, in order to bump up the calorie content,” Levine wrote. They were required to include a serving of butter and to include whole milk and a pudding or other dessert.

‘Vigorous’ kids

The Cold War fostered a renewed and somewhat different drive to make American children strong, said Chin Jou, a Harvard University historian. In 1956, President Dwight D. Eisenhower created the President’s Council on Youth Fitness and Sports, an idea endorsed by his famously active successor, John F. Kennedy. The effort to have students run, long-jump, and perform pull-ups and other calisthenics continued through the 1970s. The idea was “to make sure kids were vigorous and healthy,” Jou said. “It was a symbol of American democracy wrapped up in how the population looked.”

Little did Americans know that their children’s fitness would soon face new threats on multiple fronts. One stealthy enemy was created in a government laboratory in Japan, where, around 1970, scientists figured out how to mass produce a new sweetener: high-fructose corn syrup, often abbreviated HFCS.

Because U.S.-subsidized corn was cheap, Jou said, HFCS was less expensive than sugar, and manufacturers were able to sell enormous servings of soft drinks and other sweetened foods for modest prices. To consumers, she said, it looked like a “great deal.”

One reason the consumers may not have realized that it was a bad deal health-wise was that the public health community was focused not on sugar but on fats — warning Americans against eggs, cheese, cream and meat. In 1977, Sen. George McGovern’s Senate Select Committee on Nutrition and Human Needs issued guidelines urging a major reduction in fats and an increase in complex carbohydrates. Industry responded with an array of low-fat and fat-free products: cake, cookies, bread, ice cream and beverages.

Americans did cut down proportionally on fats but, ironically, they started to get fatter — much fatter. Statistics from the Centers for Disease Control and Prevention show that rates of obesity in children and adults, which had been climbing through the ’70s, started to shoot upward around 1980. For children, obesity tripled from about 5 percent in 1980 to about 15 percent in 2000.

Although Harvard’s Jou noted that there was “no one culprit or explanation” for the startling rise, Gary Taubes, author of “Good Calories, Bad Calories,” emphasizes the effect of the anti-fat campaign. With eggs and bacon off their menus, he argued, many Americans filled their plates with cereal, toast and other foods high in carbohydrates. Furthermore, the new low-fat substitutes were often laden with high-fructose corn syrup and starch. Portion sizes grew.

At the same time, schools all over the country were allowing vending machines into their hallways, and cafeterias were coming to resemble shopping-mall food courts. Part of the reason was financial: They attracted paying students. Fast-food and soda companies also offered funding in exchange for adding their logos to, say, football scoreboards. But such contracts “turned out to be a bargain with the devil,” said Kelly Brownell, a Duke University expert on obesity. Add in the aggressive food advertising on television and online, he said, and kids of the 1980s and ’90s faced a “toxic food environment.”

“Industry realized that children are a valuable market and targeted them, hoping to build lifelong loyalty to brands,” Brownell said. Manufacturers came up with an array of child-specific foods — sweetened yogurts and juices, and popular combinations such as Happy Meals and Lunchables. “These foods tend to be unhealthy,” he said.

Behind all the food issues was another threat to fitness: Children were getting less exercise. For reasons including suburban sprawl and safety concerns, fewer students were walking and biking to school. Many schools cut out physical education and reduced the time kids spent running around at recess. “Atari and Nintendo and the Internet exacerbated that,” Jou said.

A sad paradox

Although it may have taken most Americans until near the end of the 20th century to recognize childhood obesity as a public health crisis, children were quick to pick up on the notion that fat was not beautiful.

“I’m sure grossly overweight kids have always been the subject of ridicule,” said Stearns of George Mason, author of “Fat History: Bodies and Beauty in the Modern West.” But by the 1920s, even mildly overweight kids were called “fat,” and new taunts were heard in the schoolyard: “Fatty fatty two-by-four, can’t get through the bathroom door.” “Here comes the bride, big, fat and wide.”

Many doctors at the time dismissed overweight as an issue of vanity, historians say. But there were a few exceptions, including a physician named Lulu Hunt Peters — “Dr. Lulu” — who in 1924 wrote a book called “Diet for Children (and Adults) and the Kalorie Kids.” It included letters written by young girls lamenting rejection, taunting and the relentless message from their peers that they were too fat to even hope for a date.

As the century continued, it became ever harder to be thin enough. In 1921, Miss America was 5-foot-1 and weighed 108 pounds, giving her a body-mass index in the lower half of the normal range. Sixty years later, Miss Americas were, on average, only a couple of pounds heavier but five inches taller. By 1995, according to “The Body Project,” by historian Joan Jacobs Brumberg, teenage girls reported that the ideal size was 5-foot-7 and 110 pounds — skinnier than their real-life average.

Even at the “fat camp” that author Marcia Millman visited for her 1980 book, “Such a Pretty Face,” an anti-fat prejudice persisted. Thinner campers shunned heavier ones, and overweight boys reported that they would not date a heavy girl because, as one 17-year-old boy put it, “A girl should be petite. Girl goes with petite like pie goes with coffee or bagels go with cream cheese.”

So at the same time that childhood obesity was skyrocketing, young people — especially girls — were exposed to ever-skinnier standards of beauty. Cases of anorexia surged. In a sad paradox, American culture had managed to make kids both heavier and more miserable about their bodies than ever before.

Recognizing the epidemic

By the dawn of the 21st century, the public health community coalesced around the idea that overweight and obesity were serious threats to the nation’s youth. The journal Pediatrics published a commentary in November 2002 titled “Childhood Obesity: A New Pandemic of the New Millennium.” The following July, Surgeon General Richard Carmona gave high-profile testimony before a congressional committee in which he referred to childhood obesity as a “crisis” and an “epidemic.”

Health officials reported a startling rise in Type 2 diabetes among children, with cases diagnosed in children as young as 8 or 9. As Duke’s Brownell noted, the disease used to be called “adult onset” — but it has had to be renamed. And it’s more dangerous for children than adults, he said: The high blood sugar that marks the disease inflicts cumulative damage, so those who develop it while still young face a much higher risk of blindness, permanent heart damage and premature death than those whose onset occurs in middle age.

By the time first lady Michelle Obama launched her “Let’s Move” campaign in 2010, it was almost impossible for anyone paying attention to be unaware of the crisis. The attention has had some effect, with recent studies showing the first signs of a leveling off of childhood obesity. But the battle is far from over.

On the bright side, Brownell said, public opinion has turned against industry’s marketing of unhealthy foods to children — and that’s now clearly understood to include those loaded with sugar or high-fructose corn syrup. “The country has agreed that schools should not be a place where predatory food activity should take place,” he said.

The first lady “gets it,” he said. “She understands this is not a problem of personal irresponsibility, but that corporate American needs to change — we need to change the environmental conditions that are driving the problem.” And, increasingly, the public gets it, too, he said. “We’re seeing campaigns directed at changing public policy rather than imploring people to be different.”

Faye Flam is a freelance science writer and author of the Lightning Rod blog.