We've all sat in front of the TV and munched on some Cheetos or potato chips, only to reach into the bag and find that it's empty and we're still hungry. It turns out there's a scientific reason that those salty snacks aren't filling you up no matter how much you eat. It's called vanishing caloric density.A common characteristic of snack chips is that they're easily breakable and tend to melt in your mouth. In his book "Why Humans Like Junk Food," food scientist Steven Witherly, zeroed in on Cheetos Puffs, calling them "one of the most marvelously constructed foods on the planet in terms of pure pleasure." Witherly explained that it is Cheetos Puffs' ability to quickly melt in your mouth as the snack's sinister appeal, as it tricks the brain into thinking that you've consumed no calories and keeps you hungry as a result. Boom! Science.