Which psychological disorder involves loss of appetite and excessive weight loss not caused by a physical disease?

The disorder characterized by a significant loss of appetite and excessive weight loss that is not linked to any physical illness is anorexia nervosa. This is a serious mental health condition that goes beyond just a desire to lose weight; individuals with anorexia nervosa often have an intense fear of gaining weight and may engage in restrictive eating behaviors, excessive exercise, or other harmful practices to control their weight. The psychological aspect is critical, as it involves an altered perception of body image and self-worth, deeply impacting the individual's mental and emotional health.

While anorexia is often used as a shorthand term in casual conversation to describe the disorder, it specifically refers to the broader category of eating disorders and does not encompass the specific criteria that define anorexia nervosa. Other options like anemia and anxiety disorder do not directly relate to the significant weight loss and lack of appetite driven by psychological factors that define anorexia nervosa.