• Conditions associated with very lean body shape (e.g., malnutrition/starvation, anorexia nervosa, cachexia caused by various etiology such as cancers, inflammatory disorders, hyperthyroidism, adrenal insufficiency, HIV associated wasting, diencephalic cachexia, etc.)• Constitutional thinness• Severe insulin resistance due to insulin receptor mutations• Acromegaly/pseudoacromegaly. The gene discussed is INSR; the disease is cancer.