The aim of this study was to evaluate the effects of sibutramine on plasma leptin levels, body weight and glucose metabolism in non-dieting women. Fourteen healthy, non-diabetic, obese women were studied before treatment, after 1 week of placebo administration, and after a 2-week course of sibutramine (110 mg/day). At each of these stages, we assessed body composition, measured the levels of plasma leptin, C-peptide and various biochemical parameters, and also recorded plasma insulin and glucose levels during oral glucose tolerance tests. After 1 week of placebo treatment, there were no significant changes in any of the parameters. However, two weeks of 10 mg/day sibutramine dropped plasma leptin levels from a mean (+/-SE) of 48.84+/-4.54 to 42.84+/-4.74 ng/ml (p<0.04), reduced BMI from 39.36+/-2.01 to 38.57+/-1.93 kg/m(2) (p<0.002), and decreased insulin resistance (IR, as measured using the homeostasis model assessment of insulin resistance) from 5.59+/-0.85 to 3.66+/-0.43 (p<0.02). There was no correlation between the reduction in leptin concentration and the decrease in BMI, fat mass, percent body fat, IR, C-peptide, or the area under curve for glucose or insulin. There was also no correlation between the decrease in leptin levels and the increases that occurred in the insulin sensitivity index or the hepatic sensitivity index. The results showed that treatment with 10 mg/day sibutramine significantly reduces BMI, IR and leptin levels in non-dieting obese women. (C) 2002, Editrice Kurtis.