AIM To evaluate the effect of chitosan on rat body weight, concetration of plasma leptin and serumtestosterone.METHODS Five groups of rats were respectively given access to basic diet, high fat diet and high fat dietwith different doses of chitosan (1.5%,3.0% and 6.0% of chitosan in high fat diet respectively) for 7 wk.All rats were weighed once a week. By the end of wk 7, the animals were sacrificed and their blood sampleswere taken, the concentration of plasma leptin and serum testosterone were determined by RIA Kit method.RESULTS At the end of wk7, the average body weight of rats treated with high-fat diet was 67.3 gheavier than that with the basic diet, however, the average body weight of rats treated with high doses of chitosan in high-fat diet was 56.3 g lighter than that with high-fat diet (P < 0.01). In addition, plasma leptinconcentration in rats treated with high fat diet was significantly different from those with basic diet(P