Like any carefully engineered product, every chip and cheese puff can be reduced to a list of deliberate ingredients and scientific formulas. And it all starts with sugar, fat, and salt.
Food makers know that humans have been hard-wired since the Stone Age to crave those three key elements, says Moss.
Back in prehistoric times, these ingredients were so rare that gorging on them when they were available was important for survival. Today, however, artificially sweet, fatty, and salty foods are cheap and plentiful—so your primal instincts can set you up to binge again and again.
First, there’s the salt. Junk food manufacturers use it to add flavor and disguise the icky taste of the preservatives that keep processed foods fresh on the grocery store shelf. At 10 cents a pound, salt is a lot cheaper than fresh herbs and spices—plus it helps draw out the saliva that melts these delicious foods in your mouth.
Next, food makers add fat. It’s not a taste like sweetness or bitterness, but it produces a powerful sensation they call mouthfeel. “It’s the same tactile feeling you get when you bite into a warm, gooey grilled cheese,” Moss says. “It sends a strong pleasure signal to the reward center of your brain.” (Scientists have figured out that the most addictive foods get at least half of their calories from fats.)
Then there’s sugar—and you already understand how hard that is to resist. But junk food manufacturers also know that when there’s too much sugar in a product, your brain will signal you’ve had enough. So they bring in scientists to calculate just the right amount to make sure you keep on eating. They call that the bliss point: the perfect spot where your body craves more without registering that you’re full.
“These companies have marched around the grocery store and engineered bliss points for everything,” Moss says, “even foods that aren’t supposed to be sweet, like spaghetti sauce, yogurt, and bread.”