Cancer cachexia is the loss of muscle tissue which causes fatigue, weakness, pain, and poor quality of life. Chemotherapy is a standard cancer treatment with notorious side effects, including the loss of muscle mass. This double-barrelled attack on healthy lean mass can compromise treatment planning and patient quality of life. In this talk I will present our models for cancer cachexia and chemotherapy-induced cachexia and discuss the implications of cachexia on treatment planning.