The aim of the study was to investigate the effects of (1) macronutrients on food intake, body composition and serum resistin and adiponectin and (2) sibutramine(S) on the above parameters in rats fed with isocaloric diets. Three groups of male Wistar rats (n=63) were fed with high fat diet (HFD), high carbohydrate diet (HCD) or high protein diet (HPD) for 13weeks. In the last 3weeks each group was divided into three subgroups and received S 5mg/kg or 10mg/kg, or vehicle. Body weight was measured weekly, gastrocnemius muscle, perirenal, retroperitoneal and epididymal fat were isolated, fat/lean ratio was calculated and serum adiponectin and resistin were assayed. S did not affect lean body mass in any group. HFD was associated with elevated fat/lean ratio regardless of S administration. S at 10mg/Kg decreased fat/lean ratio in the HCD and HPD and adiponectin in the HFD group. S did not affect resistin in any group. Adiponectin was paradoxically elevated in the HFDS10 compared to the HCD or HPD S10 groups. Resistin was lower in the HCD compared to the HPD and HFD groups. Results suggest a preferential effect of S on body fat. The detrimental effect of S on adiponectin can be attributed to its sympathomimetic properties. Adiponectin was paradoxically elevated in the HFD and resistin in the HPD group, results that require further investigation.