There is no black and white definition of disordered eating. A general explanation of disordered eating is using food (whether restricting or overeating) to cope with stressors. This is almost identical to the definition of an eating disorder; the difference is the extremity of this behavior. Those with an eating disorder such as anorexia nervosa or compulsive overeating are flirting with danger as they ask their bodies to exist on far too few or far too many calories. 

This is not to say that disordered eating is not as important. Managing disordered eating is crucial as it is often an indicator of other stressors in your life. For some people, if left untreated, disordered eating can develop into a full on and dangerous eating disorder. 

As indicated above, disordered eating whether over or under eating is the result of unresolved emotional issues, and everyone is different; different emotional stressors and different in the manner of dealing with these issues. Seeking help when you find yourself managing stress with too much or too little food may best for your mental and physical health.