How to get out of the habit of eating junk food? What causes habitual eating of junk food?
How can one get out of the habit of eating junk food?
Paul McKenna would be jumping on this question had it been a self-help question :)

Some of the causes/factors in habitual eating and strategies to combat habitual eating are described below.

Causes and factors of habitual eating


Excessive hunger may precipitate an episode of binge eating compared to average hunger levels (Haedt-Matt &amp; Keel, 2011).
Negative moods, an immediate break-down of emotion and impulse regulation attempts can contribute to episodes of binge eating in Binge Eating Disorders (BED) (Munsch et al., 2012). Binge-eating behaviours can thus arise from negative moods as a substitution for positive strategies to alleviate those negative moods.
Depressive symptoms can predict the onset of overeacting and binge eating (Skinner et al., 2012). Similar to point two, these behaviours are a form of maladaptive coping mechanisms against negative affects.


Strategies to combat habitual eating


Cognitive Restructuring (CR) - Cognitive restructuring involves a problem-solving methodology where an individual identifies the maladaptive cognitions that are causing the unhelpful behaviour (Moffitt et al., 2012). This consists of rationalising and challenging disruptive thoughts that can cause the specific craving or binge eating behaviour. Moreover, it can involve the process of the replacement or modification of those disruptive thoughts into more healthy, positive thoughts.
Cognitive Defusion (CD) - Defusion from thoughts about food can improve the probability of distancing oneself from the temptation of food cravings (Moffitt et al., 2012). This involves acceptance (not passive resignation) of cravings and temptation of binge eating and build the experiential willingness to be open to these thoughts and temptations. For example, defusion would involve observing the thought associated with the craving - 'I notice I'm having the thought that I need to eat some chocolate' compared to a seemingly factual statement like 'I need to eat some chocolate'. The individual acknowledges the thought, thanks themselves and lets the thought dissipate in time.


References


Haedt-Matt, A.A. &amp; Keel, P.K. (2011). Hunger and Binge Eating: A meta-analysis of studies using ecological momentary assessment. International Journal of Eating Disorders, 44(7), 573-578
Munsch, S., Meyer, A.H., Quartier, V. &amp; Wilhelm, F.H. (2012). Binge eating in binge eating disorder: A breakdown of emotion regulatory process? Psychiatry Research, 195, 118-124
Skinner, H.H., Haines, J., Austin, S.B. &amp; Field, A.E. (2011). A prospective study of overeating, binge eating, and depressive symptoms among adolescent and young adult women. 
Journal of Adolescent Health, 50, 478-483
Moffitt, R., Brinkworth, G., Noakes, M. &amp; Mohr, P. (2012). A comparison of cognitive restructuring and cognitive defusion as strategies for resisting a craved food. Psychology &amp; Health, 27(2), 74-90