The metabolic effects, and the composition of the tissue lost, in weight reduction by obese patients on treatment with fenfluramine.

1. Three groups of obese patients were treated for periods of up to 6 months. One group of 52 individuals received 80-120 mg fenfluramine daily. The second group of 20 people had placebo tablets. The third group of 28 patients were on a dietary restricted régime.2. Only the fenfluramine and dietary treated groups lost weight but there was no evidence of an increased metabolic rate after fenfluramine, either at rest or in standardized exercise. During the first month of treatment the mean weight loss in the group treated with fenfluramine was greater than that in the group treated by diet alone, but the difference was not significant (P<0.05). By the third month of treatment the mean weight loss was smaller in both groups, particularly in the women.3. The composition of the tissue lost in the weight reduction had a mean fat content of 75% and did not differ significantly between the fenfluramine group and the diet-restricted group, except in women.