An assessment of the thermogenic effects of fluoxetine in obese subjects

Fluoxetine is an antidepressant drug with weight reducing properties. To assess whether fluoxetine has an ability to promote diet induced thermogenesis (DIT), 30 obese subjects (BMI 30-45 kg/m2) underwent a double blind, randomized, cross-over trial of 60 mg fluoxetine versus placebo. A two week single blind, run-in period on placebo was incorporated into the study to allow for placebo responders. The first stage of the study lasted for 14 days followed by a six week cross-over wash-out phase and concluded with the second 14 day stage of the study. An estimate of resting metabolic rate (RMR) was measured by continuous indirect calorimetry using the ventilated hood technique. Metabolic measurements were performed on six occasions, immediately before the first tablet was taken in the first stage, 24 hours after the first tablet was consumed and on the last day of the first stage; these three recordings were repeated on the second stage of the study. On each occasion a control reading of RMR was taken for 30 minutes then DIT was measured for 90 minutes following a lemon and glucose drink (1 g/kg body weight). Whilst a significant weight reduction (1.16 kg, P less than 0.05) occurred in the active stage, no such effect was achieved in the placebo phase. No differences were found between the two stages with regard to RMR, total DIT, peak DIT and time taken to reach peak DIT. We conclude that fluoxetine does not stimulate metabolism and that the weight reduction after 14 days therapy is due to other mechanisms.