To investigate the effects of oral L -carnitine (LC) supplement on body weight, fat content,and serum levels of insulin and leptin in obese rats, male Wistar obese rats,induced by high fat diet,were randomly divided into four groups and fed LC of 0,125,250,500 (mg/kg BW) respectively for six weeks. At the end of the experiment,body weight of the rats,fat pad around kidneys and testes and serum levels of insulin and leptin were measured. The results showed that the body weight of rats in all LC supplementation groups decreased significantly compared with that in the control group ( P <0.05). Fat pads and levels of insulin and leptin of rat in 250 mg/kg BW and 500 mg/kg BW groups were lower than those of rats in control group( P <0.05). It was concluded that LC may increase consumption of energy,decrease weight gain and weaken the intrinsic resistance to insulin and leptin in obese rats.