To elucidate the effect of rice protein level (7% and 14%) on body mass and lipids level in adult rats,male Wistar 20-week-old rats were fed rice protein (RP) and casein (CAS) adlibitum for 2 weeks.Body mass gain,deposit fat,and lipids concentration in plasma and liver were measured.Under 7% dietary protein level,no difference of body mass,growth performance,lipids in plasma and liver was found in C7 and R7.In contrast,R14 produced marked hypocholesterolemic action in comparison with C14,reflecting in the significant reduction of total cholesterol (TC),non high density lipoprotein cholesterol (non HDL-C),triglyceride (TG) in plasma (P<0.05).As a result,the atherogenic index (AI) of adult rats fed R14 was lower than those fed CAS.The liver accumulations of total cholesterol and triglyceride were significantly decreased in adult rats fed R14 as compared with C14 (P<0.05),with the increased dietary protein level.Body mass gain of adult rats fed R14 was lower than those fed C14,although no difference of body mass gain were observed in both groups of 7% dietary protein level.The present results suggest that the potential anti-obesity of RP might be closely related to dietary protein level,which may play an important role in regulation of lipids level and body mass gain.