This article from The American Council on Exercise describes why we eat when we are not hungry
It basically boils down to what we learnt when we were growing up, following habits instead of conscious decisions, and associations between eating junk or high calorie foods when feeling either happy or sad.
Social pressures play a big part, and there’s interesting information about something called the ventromedial prefrontal cortex, evolutionary reasons for wanting a dessert when we are already full, and the role of dopamine.
The message is that we need to listen to our bodies more and retrain the brain over time by changing habit patterns. Could this also be called mindful eating?