Lack of chewing is why our food is becoming more and more fatty, spicy, and sugary  (more calorie dense).  If you chew your food, the natural sweetness of grains, fruits and vegetables can be appreciated and enjoyed. 

If you wolf your food down, it needs to have a lot of refined sugar in it to taste sweet because it is going by really fast.  It needs a lot of fat and spices to coat your mouth and linger there because otherwise you won’t feel like you have eaten.

Without the satiety signal that your gut sends your brain (after 20 to 30 minutes of eating), the only indication that you are full is when you feel your stomach stretched (sometimes painfully).  Since our bodies are designed to adapt to the demands we place on them, our stomachs become larger over time. 

As we eat more, we adapt to eat even more.  And we become fatter and fatter.  Because we don't take the time to chew our food.