It is well known that trypsin inhibitors（TIs）alter exocrine pancreatic function. We found that dietary TIs decreased serum triglyceride levels in Wistar rats in a previous investigation. In this study，we tried to confirm the effect of TIs on lipid metabolism of Sprague-Dawley（SD）rats with Japanese quail ovomucoid（OM）as a TI. Five-week-old male SD rats were fed a 20% casein control diet or OM diets containing 0.1% OM，0.2% OM or 0.4% OM for 4 weeks. Rats had no change in food intake and growth rate between the control and OM fed groups. An OM fed group（0.4% OM）had lower serum triglyceride levels and no change in serum cholesterol levels. OM led to increased pancreatic protein content and trypsin and chymotrypsin activities in a dose dependent manner，but no difference in amylase activity. Liver fatty acid synthetase activity significantly decreased in OM fed groups. Therefore，we suggested that dietary OM caused increased pancreatic protein synthesis，which resulted in increased energy expenditure and decreased serum triglyceride level
