The thoughts and behaviors associated with an eating disorder are symptoms of the illness.  This is an important concept that I always cover in the very first session with a client.  By framing these as symptoms, they become much easier to talk about because it reduces the shame.  It can also be helpful to point out that what the client may view as problems have actually been his/her solutions, and while they may be destructive they are often simultaneously helpful.  

Let's look at a few examples of the functions of the symptoms as listed by Cloak and Powers¹:

• Rebel against a struct caregiver/superego and express autonomy 
• Test the therapist to see if s/he will respond in the same way as early caregivers
• Displace anxiety or shame onto fears of weight gain or hatred for the body
• Avoid recovery because it is perceived as resulting in overwhelming demands for performance
• Avoid recovery because it is equated with becoming a narcissistic extension of the therapist
• Substitute self-destructiveness related to the eating disorder for suicide
• Maintain a pathological identity
• Distract both patient and therapist from painful topics
• Precipitate rejection by the therapist because it is less painful to be rejected for unacceptable behavior than for intrinsic unacceptability
• Express emotional pain for which the patient cannot yet find the words

As you can see, the symptoms of eating disorders are incredibly complex in their functionality.  An important part of the therapeutic and recovery process is to formulate an understanding of the symptoms.  

Reference:

1. Maine, McGilley, Bunnell.  (2010). Treatment of Eating Disorders: Bridging the Research-Practice Gap. (p. 150).  London: Academic Press.