There are many theories of causation and a variety of treatment strategies. The concern about body image and weight control may be a symptom of the underlying biological disorder and not a cause. The idea of a recursive feeding loop, running amok, helps us to locate the irrational behavior at a primitive, addictive level. The rational concern is not just avoiding weight gain, but also avoiding the awful feelings and the depression that follows bingeing. Many bulimics have a split personality or different eigenstates.
Foods act as molecular switches, often changing the eigenstate abruptly.
A second state methodically gets rid of the problem. A third state acts as if neither the bingeing nor the purging are happening at all. Most bulimics are focused on weight control - this is often a ruse, a convenient and widely accepted explanation. Many fail to recognize their food addiction, and do not admit that they are ill. They are involved in typical addictive denial.