How do sociologists know that the causes of eating disorders (such as anorexia nervosa and bulimia) and obesity reflect social factors more than physical or biological factors?

Because eating disorders are very recent health problems.

Explanation:

Eating disorders are pathologies of great clinical and social importance, as they present significant degrees of morbidity and mortality, and increasingly focus the attention of health professionals. Among eating disorders, anorexia, bulimia and obesity have attracted special interest from researchers and clinicians, due to the enormous challenge these pathologies pose to the health field.

Despite the degree of dangerousness, these diseases began to appear frequently in a short time showing sociologists that these diseases reflect social factors (such as the current way of life) rather than physical or biological factors.