The effect of sibutramine on resting energy expenditure and adrenaline-induced thermogenesis in obese females

BACKGROUND: Sibutramine, an inhibitor of serotonin and noradrenaline uptake, reduces appetite to cause weight loss. This study tested the hypothesis that an increase in energy expenditure also contributes to this weight loss. In addition, the effects of sibutramine on adrenaline induced changes in heart rate and cardiac output were determined METHODS: Nineteen obese females randomly received either sibutramine 15 mg daily or placebo for 12 weeks along with dietary advice. Resting energy expenditure (REE) was measured and then energy expenditure was measured during a 30 min infusion of adrenaline (25 ng/min/kg IBW). Cardiac output and heart rate, measured by Duplex Colour Doppler ultrasonography, were similarly measured in the basal state and post adrenaline. All measurements were recorded at baseline and then after 12 weeks. RESULTS: Ten patients who received sibutramine reduced their weight by 8.1 +/- 3.8% while 9 placebo treated subjects reduced their weight by 5.1 +/- 4.4%, P = 0.13. In absolute terms, REE decreased in placebo subjects from 1500 +/- 201 kcal/24 h to 1357 +/- 231 kcal/24 h (9.4 +/- 9.9%) and in sibutramine subjects from 1540 +/- 184 kcal/24 h to 1444 +/- 128 kcal/24 h (5.3 +/- 12.0%), P = 0.77. The increased weight loss in the sibutramine group was associated with an increase in the FFM adjusted REE (2.2 +/- 16.1%) unlike the expected decrease (5.8 +/- 9.5%) in the placebo group (P = 0.11). There was some suggestion (P = 0.09) that the usual positive correlation between loss of weight and decline in REE was lost in the sibutramine group (r = -0.30) compared with placebo (r = 0.35). There was a negative correlation between loss of FFM and decline in REE/kg FFM and (P = 0.029) which was not evident in placebo (P = 0.83). Adrenaline induced energy expenditure was similar in the two groups at the end of the 12 week period and there were no significant cardiovascular changes between the two groups. CONCLUSIONS: Sibutramine limits the decline in REE associated with weight loss, equivalent to about 100 kcal/d. This could allow greater numbers of people to maintain a greater degree of weight loss.