How can I stop myself from eating when I'm not hungry?
It's often hard to realize you may be eating for reasons besides a nutritional need! You may be simply just eating out of habit, boredom, or to distract from some emotion like a need for affection, or if you're worried, upset, or angry. First, after being conscious of "why," ask God to help. Then, don't deny God's assistance or insult Him by continuing something you'd rather not do. Third, try to become even more consistently aware of your true desire to change, knowing full well that there's a direct cause and effect relationship between overeating and obesity.
It will also help to regularly recommit to your weight and health goals, instead of having that extra food. Then, do something that will cause your brain to secrete endorphins, the "happy juices."
Next time you're tempted to eat when you know you're not hungry, try some other ways to feel happy quickly: Playing a physically active game, or watching really funny stand-up comedy, or getting tickled by your partner or friends.