I believe this man has cachexia (from his hx of cancer)--which is mainly due to increased proinflammatory cytokines
After initial elimation of everything except for Cytokine effect and Tumor hormone production, I thought through it like this: We know he has small cell lung carcinoma and it can't be tumor hormone production because the three paraneoplastic syndromes of SCC are 1. ADH (would increase weight) 2. ACTH (would increase weight) 3. Antibody (Lambert Eaton, no change in weight)
So only could therefore be A!