When I'm first getting to know a new client who has a weight-loss goal, I chat to them about what they think is causing them to overeat. The client themselves usually already has these answers.
A large percentage of clients will report varying levels of emotional eating. They are eating when they are hungry, but also when they are anxious, angry, sad or bored. It's a sort of self-medication, giving yourself a hug from within.
The first line of defense is a hand written food journal, a very basic and straight forward way of helping you to be aware of what you are eating. Also incredibly important is mindfulness. Every time we go for a snack, we pause and think about why we are eating. It's very simple, just a brief moment to take stock of our motivation. The more you do this the more you become aware of why you are eating and what seems to be happening in your brain. Gradually this basic action can lead to a reduction in emotional eating.
This great Ted Talk by psychiatrist Judson Brewer explains why and how this works in relation to emotional eating and many other habits we wish to break.