Final answer:
Fairburn's Transdiagnostic Model recognizes the overvaluation of shape and weight as the central symptom in eating disorders, influencing behaviors across different disorders like anorexia and bulimia nervosa.
Step-by-step explanation:
According to Fairburn's Transdiagnostic Model, the core symptom of eating disorder psychopathology is overvaluation of shape and weight. This overvaluation serves as a central mechanism that connects various eating disorders, thereby shaping the individual's self-evaluation and leading to significant distress or disturbance in behavior. For example, in anorexia nervosa, this can manifest as extreme food restriction due to the fear of gaining weight, while in bulimia nervosa, it often involves cycles of binge eating followed by purging to control weight.