Methods of treatment in subjects suffering from diabetes mellitus or obesity are provided. The methods comprise the step of administering an active agent directly to the small intestine in the subject. In particular, the active agent may be administered directly to the duodenum in the subject. The active agents useful in the treatments described herein include analgesic agents and, in particular, antinociceptive agents such as capsaicin, resiniferatoxin, and their analogues.
