In-n-Out

Maybe our food tastes too good.
Maybe it's too easy to consume.
Maybe we should have listened to our grandmothers when they told us to chew each bite twenty times before swallowing.

When we fail to properly chew our food we don't allow the enzymes found in our saliva to break down the starches, fats and proteins we consume. Our bodies know that they need these nutrients and if it takes three times the food to get the required nourishment, the brain may be telling the body to continue to consume until the required nutrient level is met.
Sure, the ratio of calories acquired to those burned has a lot to do with weight gain - but maybe the way we eat (or 'chew') our food is just as important.