Uptown pretty much summed it up, and it's very a complex and multifactoral situation when it comes to weight loss, muscle loss from cancer treatment, cachexia, anorexia, and other side effects, especially in head and neck cancer patients who may already be nutritional deficient due to tobacco, alcohol dependency, and the tumor itself causing dysphagia, and other metabolic changes in the body. Other treatment related toxicities from chemotherapy, radiation can cause nausea, vomiting, diarrhea, mucocitis, aspiration, increased transit time, skeletal muscle loss, inflammatory responses, and a host of other problems, not to mention other medications that can cause muscle wasting like antibiotics, and a fetynal patch.