According to WebMDHealth, 75% of overeating is caused by emotions.

Situations and emotions that trigger us to eat fall into five main categories.

• Social. Eating when around other people. For example, excessive eating can result from being encouraged by others to eat; eating to fit in; arguing; or feelings of inadequacy around other people.
• Emotional. Eating in response to boredom, stress, fatigue, tension, depression, anger, anxiety or loneliness as a way to "fill the void."
• Situational. Eating because the opportunity is there. For example, at a restaurant, seeing an advertisement for a particular food, passing by a bakery. Eating may also be associated with certain activities such as watching TV, going to the movies or a sporting event, etc.
• Thoughts. Eating as a result of negative self-worth or making excuses for eating. For example, scolding oneself for looks or a lack of will power.
• Physiological. Eating in response to physical cues. For example, increased hunger due to skipping meals or eating to cure headaches or other pain.

For more info, see Weight Loss: Emotional Eating [1]