I believe that the main reason people eat when they aren't hungry is to fill the boredom. That's why I eat. I don't eat because my body is telling me I need to satiate it for survival, I eat because I'm like "Well, now what should I do?" and putting something into my mouth, chewing it, and swallowing is the best option. Am I no longer bored? Yes. Am I happy? Not really.
I'm sure you've eaten due to boredom multiple times in your life—we've all done it. We've not only done it, we've acknowledged it, but we rarely fix it. Why is it so easy to continue doing something we consciously know is bad for us and so hard to stop doing it? I don't know the science behind it but it just is!
Ways to stop boredom eating
Don't keep snacks in your home.
If you're like me, you lack self control when it comes to food. You don't eat one Oreo, you eat the whole sleeve. You don't put two scoops of ice cream into a bowl, you go at the carton with a spoon. If this sounds like you, then you need to stop keeping temptations at an arm's reach. I go to the store almost every day and only buy items I will eat that day. Trust me, I've thrown tantrums at 9 o'clock at night, opening every cupboard looking for chocolate because I'm boooored. This forces me to do something more valuable with my time and keeps me from stuffing my face with empty calories.
Leave your money at home.
It's so easy to walk past a shop and go in to buy something. There's a chocolate cafe, an ice cream shop, a cupcake shop, and a cheesecake shop all within a 1/2 mile of my flat. If I want to go for a stroll, I'm walking past these places. The best thing you can do is leave your money at home so you can't even entertain the idea of going in to "have a browse".
Don't multi-task eat
Make eating meals it's own activity. Focus on each bite, focus on the taste, and enjoy it. I suck at this. Whenever I eat, I want to watch TV and whenever I watch TV, I want to eat. I'm distracted and I don't think about what I've put into my mouth, I just know I want to keep eating because the TV show is still on. When I do this, I've now killed two birds with one stone and I've got nothing to do. Focus on eating by itself as its own task, and then move onto the next task afterwards.
Start a hobby or learn something new
Write down all the things you've wanted to do, to learn, or you're just generally curious about. Pick one and do something about it. I've recently filled that time of boredom with taking an online class because I've wanted to learn more about business. Being productive during the day is much more fulfilling than eating a tub of ice cream.
Boredom sucks, but don't let it suck you in. When you start making small steps towards being productive with your free time, you'll train yourself to get used to it and stop filling the time with food.