Among many observations on the junk food industry, Paul McFedries offers an explanation of why food makers don’t simply add more sugar, salt, and fat:
Why not just crank these ingredients up to 11 if we crave them so much? It turns out that although we generally do like more of them, when you go past a certain amount, we like the result less. That optimum amount of salt, sugar, or fat is called the bliss point. Scientists also adjust these ingredients as well as factors such as crunchiness to produce a mouthfeel—that is, the way the food feels inside a person’s mouth—that causes consumers to crave more. Technologists can also induce a flavor burst by altering the size and shape of the salt crystals themselves so that they basically assault the taste buds into submission.
The holy grail of junk-food science is vanishing caloric density, where the food melts in your mouth so quickly that the brain is fooled into thinking it’s hardly consuming any calories at all, so it just keeps snacking.
In the process, packaged-food scientists want to avoid triggering sensory-specific satiety, the brain mechanism that tells you to stop eating when it has become overwhelmed by big, bold flavors. Instead, the real goals are either passive overeating, which is the excessive eating of foods that are high in fat because the human body is slow to recognize the caloric content of rich foods, or auto-eating: that is, eating without thinking or without even being hungry. (The opposite problem is being overhungry, where you’re so ravenous that you’ll basically eat anything that’s put in front of you.) Either way, if you end up with a food baby, a distended stomach caused by excessive overeating, you’ve made a fast-food executive somewhere very happy.