Researchers at the Orlando Immunology Center in Florida investigated the long-term effects of THC (dronabinol) on 117 patients with HIV/AIDS, who lost weight. Subjects who received dronabinol for 3 to 12 months were included in a retrospective analysis. THC was shown to improve appetite and weight and to reduce nausea.

63 per cent of patients maintained or gained weight. In subjects receiving THC for 1 year, the mean weight gain was about 1700 grams. The percentage of patients experiencing loss of appetite decreased significantly from 71 per cent to 26 per cent at 1 month after start of the therapy and continued to decline throughout the trial. The percentage of patients experiencing nausea (38 per cent) decreased consistently from week 2 on.

(Source: Dejesus E, Rodwick BM, Bowers D, Cohen CJ, Pearce D. Use of dronabinol improves appetite and reverses weight loss in HIV/AIDS-infected patients. J Int Assoc Physicians AIDS Care 2007;6(2):95-100.)