Scientists have discovered that certain ultra-processed foods essentially undergo “predigestion,” which makes them seem less filling than truly whole and undigested foods. 

Food producers reduce basic food crops such as corn, wheat and potatoes to their most basic molecular components, called “slurries.” “The bulk of what is extracted is starch slurry, a milky mixture of starch and water, but we also have extracted proteins and fibers,” Starch Europe, a European starch industry association noted.

The "slurries" are then combined with artificial flavors, food coloring and such to make the many foods we consume. However, they lack fiber and protein that normally signals our stomach when we're full. Therefore, we overconsume. “In effect, you are bypassing the stretch receptor effect in the stomach,” preventive and lifestyle medicine expert David Katz told CNN. “Before the stretch receptors can even tell you, ‘Hey, we’ve had enough,’ you’ve put down twice as many calories as you need.” 

Unfortunately, the majority of adult American's calories come from these predigested foods.