Ask Smithsonian: Why Do We Love Junk Food So Much?

The jury is still out, but some are suggesting that sodas, chips and fries trick the brain into thinking no calories were consumed

What is it that keeps so many of us bellying up for double-decker burgers, dipping repeatedly and obsessively into bags of crunchy chips, and chasing it all down with super-sweet soda?

These so-called junk foods hit us right where our taste buds live and also satisfy a love of sugar that we’re born with. But the burgeoning, and in some cases, chronic, consumption of junk is driven by peer pressure and marketing—not physiological need—say nutrition experts.

“People love the way they taste,” said Marion Nestle, Paulette Goddard Professor of Nutrition and Food Studies at New York University.  But she said, that love is aided and abetted by the fortunes that manufacturers put into formulating those products, marketing them, and establishing brand loyalty. “Studies show that brand preference trumps taste every time,” said Nestle.

What is junk food? “Most people know a junk food when they see one,” Nestle said, paraphrasing Supreme Court Justice Potter Stewart’s 1964 pronouncement on pornography. The official definition, she said, is “a highly processed food of minimal nutritional value relative to calories.” That would include soft drinks, which have no nutrients, but lots of calories, and fast food, which may contain some nutrients, but they are accompanied by loads of excess salt and sugar.

Junk is considered bad for us because it rewards the brain—through pathways that are similar to those observed with the ingestion of powerfully addictive drugs—but it does not enhance the body.

McDonald’s recently has gone on the offensive, aiming, it says, to correct misperceptions about what’s in its food and to meet consumer demand for more nutrition information. But the campaign seems to be raising more questions than it answers. In one of a series of YouTube videos put out by the company, it reveals that there are 19 ingredients in its French fries. The list includes salt and potatoes, but also a handful of preservatives, and different oils—some hydrogenated, which have known health risks—plus wheat, and “natural beef flavor,” among other additives.

Manufacturers create foods to meet multiple needs: being able to make mass quantities that have a consistent quality; making something that’s tasty and will sell well; and hitting on a formula that will keep us coming back for more. Journalist Michael Moss detailed food makers’ huge junk food R&D and marketing enterprises in a 2013 story for the New York Times and a later book.

Moss documented a multi-billion-dollar engineering process that creates flavor profiles designed to appeal to humans’ innate love of sugar, and the additional lip-smacking triumvirate of salt, fat and crunch. The average consumer wouldn’t necessarily discover these food products without some help. According to Moss, the $1 trillion food industry, with so much at stake, pays to have its processed foods placed at eye level on grocery store shelves. And of course, there are huge advertising campaigns, and tie-ins with celebrities, TV shows, cartoons, and movies.

Children are most vulnerable. The Center for the Science in the Public Interest, a nutrition watchdog organization, says that studies show that the ad blitzes and tie-ins easily capture childrens’ attention, who not only start building brand awareness and loyalty, but in turn are often a linchpin in influencing what their parents buy.

CSPI, along with the American Academy of Pediatrics, among other groups, have long pressured fast food chains and food conglomerates to rein in marketing to kids and to offer healthful alternatives. As a result, Burger King just recently joined several other fast food purveyors in saying it will remove soda from its kids’ menus.

Why is this important? CSPI, in a 2006 report urging responsible food marketing to children, said that since the 1990s, the rates of obesity have doubled in children and tripled in teens, and that most are eating nutritionally-poor diets that are too high in calories, saturated and trans fat, refined sugars, and salt, and too low in fruits, vegetables, whole grains, and calcium. Everyone’s looking ahead to a future full of adults with serious chronic illnesses like diabetes, heart disease and cancer.

Are junk foods addictive? Moss believes so. He described how Frito-Lay’s Cheetos product might help hook people, with what one scientist described as vanishing caloric density—the ability to trick the brain into thinking no calories were being consumed, even as the quick-melting corn snack drove the eater into wanting—and eating—more.

But Nestle said the jury is still out. “I don’t think you need to invoke addiction to explain why people like to eat them,” she said. “They taste good and satisfy hunger. Whether they are good for long-term health is an entirely different matter.”

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