How does cannabis stimulate appetite, and is it effective for cachexia?

THC stimulates appetite through CB1 receptor activation in the hypothalamus, particularly the arcuate nucleus, which regulates hunger hormones. Mechanisms include: enhanced olfactory sensitivity (food smells more appealing), increased ghrelin release, reduced leptin sensitivity, and activation of hypothalamic neurons that normally signal starvation. This is the basis of the "munchies." For cachexia (wasting syndrome in cancer and HIV/AIDS), dronabinol (synthetic THC) is FDA-approved. However, clinical trial results are mixed: a 2006 Cochrane review found dronabinol modestly improved appetite but not body weight or quality of life vs. placebo in cancer cachexia. Megestrol acetate (a progestational agent) outperformed dronabinol in a head-to-head trial. For HIV-associated wasting, evidence is somewhat stronger. The appetite-stimulating effect is more consistent than the weight-gain effect.