eating food has its chemical hormones releases from the brain purse to the bloodstream which turn back to the brain and controlled it mood. a lot of person's especially those that grow up from poor environment or poverty settings losses a self awareness. when they chewing the food all the muscles in the head responds and work tirelessly.

their face and mouth appeared disgusting, they concentrate and focus on the food like wild loans. self consciousness or awareness how they look or how people look at that at that moment is zero.

its a mental phys problem. just like a mad persons that are not aware of themselves.